Ololade Olatunji Editor

Natural
Polymers
Industry Techniques and Applications
Natural Polymers
Ololade Olatunji
Editor

Natural Polymers
Industry Techniques and Applications

13
Editor
Ololade Olatunji
Chemical Engineering Department
University of Lagos
Akoka, Lagos
Nigeria

ISBN 978-3-319-26412-7 ISBN 978-3-319-26414-1  (eBook)

DOI 10.1007/978-3-319-26414-1

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Preface

The word polymer is derived from the Greek word “poly” meaning many and
“meros” which means parts. Hence polymer refers to molecules made up of many
parts. More specifically, polymers are defined as molecules made up of repeated units
of smaller molecules. Although recent decades has seen a boost in the polymers in
various industries from pharmaceutical to construction to fashion industries where
designer shoes and bags made from synthetic and natural polymers from both plants
and animals have become commonplace, polymers have been in existence since the
very existence of life. DNA, cellulose, cotton, and rubber are all polymers occurring
in nature since the beginning of the ages. Processing of natural polymers has been
taking place since the early humans who have long woven and dyed fibers of silk,
wool, and carbohydrates from flax and cotton. Natural rubber (Hevea brasiliensis)
has been used by the early South American civilization for waterproofing and elastic
materials (Seymour and Carraher 1992). Today processing techniques of natural and
synthetic polymers have become more advanced with broader applications from scaf-
fold in tissue engineering (Chap. 5) to films for packaging (Chap. 7). An account of
the development of synthetic polymers over the years exists in the literature (Seymour
and Carraher 1992) showing the development of polymers from mainly natural poly-
mers such as wool, cotton, flax, leather cellulose, and silk in the early 1800s to the
development of vulcanized rubber in 1839. Later developments led to development
of bakelite, cellulose acetate, and cellulose nitrate between 1907 and 1923. Later
in the 1930s–1940s as understanding of polymers gradually developed, more poly-
mers such as poly(methyl methacrylates), polyvinyl acetate, and polystyrene were
­developed. Polycarbonate, polypropylene, high-density polyethylene, flurocarbones,
silicones, and polyurethanes and a host of other polymers were developed between
1940 and the late 1950s, where polymer saw a huge development. Later years saw
development of more polymers such as Kevlar and development of more varied forms
of pre-existing polymers to improve properties such as electrical conductivity. Today
biopolymers such as Polylactic acid and chitosan have gained increasing attention in
industries in applications such as 3D printing and tissue engineering.
Polymers have for centuries been an attractive alternative to metals due to the
rather unique properties they possess. These properties include their tendency to

v
vi Preface

be biocompatible, relative lighter weight, and ease of chemical modification com-

pared to metals. Natural polymers herein refer to polymers obtained from natural
sources with minimal or no alteration to their chemical structure. This book looks
at their extraction, purification, modification, and processing for various industrial
applications. Although a large portion of the organic chemistry industry is dedi-
cated to producing systemic polymers, natural polymers play a significant role in
many industries ranging from biomedical, pharmaceutical, to construction indus-
tries. These are discussed in this book.
Chapter 1 discusses the classification of natural polymers within the scope of
the book. Natural polymers are classified based on their sources in nature as poly-
saccharides, proteins, polynucleotides, polyisoprenes, and polyesters. The chap-
ter goes further to give descriptions and examples of natural polymers which fall
within these classifications.
Chapter 2 discusses the processing and characterization techniques that are
applicable to natural polymers of industrial relevance. For each processing and
characterization technique discussed, example case studies of natural polymers
which the techniques apply to are provided. The chapter discusses some recent
works that present innovative approaches to processing of natural polymer-
based materials. This includes techniques for production of polymer composites.
Electrospinning, extrusion, film casting, and spin coating are some of the pro-
cesses discussed. Characterization methods presented are mainly methods such as
TEM, XRD, and NMR with some example results of their applications to natural
polymer-based materials for various applications.
In Chap. 3 methods for extraction, purification, and modification of some natu-
ral polymers of industrial relevance are discussed. These include acid and alkali
methods of extraction of gelatin from various sources, extraction of starch, chitin,
and chitosan among others. In doing so the structure of the polymers are also dis-
cussed as well as the structural modifications that they undergo in the process of
extraction and modification.
Chapter 4 discusses some biomedical applications of natural polymers. This
includes applications in scaffolds, wound healing, and repair of skin and bones.
The chapter gives examples of cases where natural polymers either alone or
blended with other materials are used in such applications. Gelatin, chitosan, and
cellulose have shown wide application in this particular industry.
Chapter 5 discusses applications of natural polymer in the food industry. This
chapter does not greatly focus on food packaging as application of natural poly-
mers in packaging is discussed in a separate chapter. The chapter looks at appli-
cation of natural polymer-based microparticles, gels, and emulsions in the food
industry with some example case studies.
Chapter 6 looks at the recent applications of natural polymers used in pack-
aging, with particular focus on various polymer blends. This chapter takes the
approach of pointing out some of the challenges in the packaging industry and the
role natural polymers play in this. Here food packaging, both edible and noned-
ible, as well as pharmaceutical packaging are discussed as they cover a significant
portion of the packaging industry.
Preface vii

Chapter 7 discusses the application of natural polymers in engineering with a

large part focusing on drilling engineering. The first part of the chapter describes
the role of natural polymers in the nonrenewable energy industry (drilling fluids).
In doing so the problems of drilling fluid loss during its circulation in oil field
wells and its solution by using natural polymers are also discussed. The second
part deals with the role of natural polymers in the renewable energy industry, par-
ticularly as biomass; this part reviews the types of renewable energy produced
from biomass. The third part focuses on the role of natural polymers in wastewater
treatment technology.
The application of natural polymers in the cosmetics industry is discussed in
Chap. 8, mainly polysaccharides and proteins obtained from vegetable, animal,
and biotechnology origins. The use of cellulose derivatives which are widely used
for their physicochemical properties and cosmetic benefits are also discussed. The
versatile role of natural polymers as stabilizers, modifiers, or other additives is dis-
cussed. Examples of cosmetic formulations in the cosmetic industries are presented.
Natural polymers are sometimes alone, but more often in combination with synthetic
polymers to broaden their applicability in hair care, skin care, or toothpaste products.
In Chap. 9 the application of natural polymers in the pharmaceutical industry is
discussed. This chapter covers a broad area which includes transdermal drug deliv-
ery, oral, topical, nasal, and ocular drug delivery, among others. Natural polymers
as hydrogels, crosslinked with other natural and synthetic polymers in their vari-
ous pharmaceutical applications are discussed.
The environmental impacts of natural polymers are discussed in Chap. 10. The use
of natural polymers in place of synthetic polymers or in combination with synthetic
polymers poses some advantages as well as disadvantages. Consideration should be
given to the overall impact on the environment during extraction, purification, modifi-
cation, and processing of natural polymers for various applications. Case studies in the
case of lignocellulose-based natural polymers are considered alongside others.
Chapter 11 covers the economic impact of natural polymers. The chapter in a
couple of pages highlights some natural polymers of economic importance. The
chapter then looks at the global impacts of natural polymer in various economies
mainly UK, US, Brazil, and some African regions.
In Chap. 12 some future prospects of natural polymers in specific industries
are discussed. This includes some novel developments which point to the possi-
ble direction of natural polymer applications and processing in the various indus-
tries in the future. The future economic prospects of natural polymers are also
discussed in this chapter with reference to some reported economic reports. This
leads to the final chapter which gives some concluding remarks for the book.

Reference

Seymour R, Carraher C (1992) Polymer chemistry: an introduction, 3rd edn. Marcel Dekker,
Inc., New York
Contents

1 Classification of Natural Polymers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Ololade Olatunji
2 Processing and Characterization of Natural Polymers. . . . . . . . . . . . 19
Ololade Olatunji and Olsson Richard
3 Extraction, Purification, and Modification of Natural Polymers. . . . 63
Abdalbasit Adam Mariod
4 Biomedical Application of Natural Polymers. . . . . . . . . . . . . . . . . . . . 93
Ololade Olatunji
5 Application of Natural Polymers in Food. . . . . . . . . . . . . . . . . . . . . . . 115
Marilyn Rayner, Karolina Östbring and Jeanette Purhagen
6 Current Application and Challenges on Packaging Industry
Based on Natural Polymer Blending. . . . . . . . . . . . . . . . . . . . . . . . . . . 163
S.T. Sam, M.A. Nuradibah, K.M. Chin and Nurul Hani
7 Application of Natural Polymers in Engineering. . . . . . . . . . . . . . . . . 185
Amany A. Aboulrous, Tahany Mahmoud, Ahmed M. Alsabagh
and Mahmoud I. Abdou
8 Cosmetics and Personal Care Products. . . . . . . . . . . . . . . . . . . . . . . . . 219
Géraldine Savary, Michel Grisel and Céline Picard
9 Pharmaceutical Applications of Natural Polymers . . . . . . . . . . . . . . . 263
Atul Nayak, Ololade Olatunji, Diganta Bhusan Das
and Goran Vladisavljević
10 Environmental Impact of Natural Polymers . . . . . . . . . . . . . . . . . . . . 315
Witold Brostow and Tea Datashvili

ix
x Contents

11 Economic Impacts of Natural Polymers. . . . . . . . . . . . . . . . . . . . . . . . 339

Adeshola Raheem Kukoyi
12 Future Perspectives. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
Ololade Olatunji, Géraldine Savary, Michel Grisel, Céline Picard
and Atul Nayak
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
Chapter 1
Classification of Natural Polymers

Ololade Olatunji

1.1 Introduction

Natural polymers by themselves are a class of polymers which refer to polymers

sourced from nature (plants or animals). They include mainly carbohydrates and
proteins which exist in plants and animals providing mainly structural support.
Other polymers include thermoplastics, thermosets, elastomers, and rubbers. The
focus of this book is primarily on natural polymers. This refers to polymers that
are derived through extraction from their bulk form in nature, for example, cellu-
lose or lignin extracted from wood. This also includes polymers produced by bio-
logical process such as bacteria synthesis or fermentation.
Like synthetic polymers, natural polymers can be grouped based on their for-
mation method as addition and condensation polymers. Most natural polymers are
condensation polymers which are formed as a result of monomer units combining
to form a small molecule (usually water) as a by-product. Additional polymers are
those formed by direct combination of the monomer units making up the polymer
without any by-product. Polymers existing in nature can be grouped into six main
classifications with respect to their sources: Proteins, polysaccharides polynucleo-
tides, polyisoprenes, polyesters, and lignin (Atkins 1987). In Table 1.1, a list of
polysaccharides from various sources is provided (Olatunji et al. 2014; Brostow
2010; Abdelfadeel 2012; Rinaudo 2005).

O. Olatunji (*) 
Chemical Engineering Department, University of Lagos,
Akoka, Lagos, Nigeria
e-mail: lolakinola@gmail.com

© Springer International Publishing Switzerland 2016 1

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_1
2 O. Olatunji

Table 1.1  List of some polysaccharides from various sources

Source Polymer
Cells walls of plants Pectin
Seeds and roots Galactomannans
Seaweeds Carragenans, alginates, agar
Animal cell walls Hyaluronan
Shells of aquatic animals Chitin
Wood Cellulose, lignin, hemicellulose
Skins and bones of animals and scales of fish Gelatin
Bacteria Xanthan, hyaluronan, gellan
Fungi Cardlan, scleroglucan,
schizophyllan

1.2 Polysaccharides

These are homopolymers of glucose or amino sugars linked by acetic bonds.

Polysaccharides are known to be by far the most abundant renewable resource in
the world. Overall, the amount of polysaccharide produced from synthesis from
plants by the sun exceeds that produced synthetically on an annual basis by several
orders of magnitude (Dumitriu 2005).
Polysaccharides are of various types depending on their structure or function.
In terms of function there are three main types; storage polysaccharides such as
starch and glycogen, structural polysaccharides such as cellulose and chitin, and
gel forming polysaccharides such as alginic acid and mucopolysaccharides (Yui
2005). They can also be branched or straight chained polymers, ionic or nonionic
(cationic and anionic) polymers.
The major storage polysaccharides are starch (amylase and amylopectin) and
glycogen (Yui 2005), while the most common structural ones are chitin and cel-
lulose. Chitin being the structural polysaccharides in some animals such as crus-
taceans while cellulose is the main structural component of plants alongside
hemicelluloses, pectin, and lignin. Hyaluronan is another structural polysaccharide
found in human cells. Hyaluronic acid is also an anionic polysaccharide.
The overall physiological property of each polysaccharide depends on the
monopolymers it contains as well as on their orientation within the polymer struc-
ture (Kajiwara 2005). Many polysaccharides show irregular properties unlike syn-
thetic polymers which makes their classification and characterization somewhat
challenging. An example is in the case of amylopectin, where due to its highly
branched nature, by laws of polymer science should ideally be noncrystalline.
Yet amylopectin takes a semicrystalline form (Burchard 2005). This has for many
years kept many researchers inclined toward studying synthetic polymers rather
than natural polymers, especially polysaccharides that show many irregularities in
1  Classification of Natural Polymers 3

their structure and properties. However, polysaccharides have become more attrac-
tive due to their biodegradable and biocompatibility tendencies.
The following paragraphs summarize the structure and function of each of
these polysaccharides.

1.2.1 Cellulose

Cellulose as the principal component of plant cell wall makes up about half of
the biomass of photosynthetic organisms, thus making cellulose possibly the most
abundant molecule on earth. Alongside other components such as lignin, pectin,
and hemicelluloses, it makes up the cell wall which is the distinguishing differ-
ence between animal and plant cells. The application of cellulose goes way back
to the Chinese dynasties and Egyptian pharaohs where evidence exists of their
use in writing materials and lingerie (Perez 2005). For many centuries cellulose
has been abundantly sourced from wood, cotton, hemp, linen, jute, kenaf, sugar
beet cereal straws, flax and is widely exploited for various industrial applications.
Applications of cellulose range from clothing pulp and paper to food conferring
huge economic relevance (Perez 2005). Other sources of cellulose include bacte-
ria (e.g., Acetobacter), algae (e.g., Valonia and Microdicyon), and marine animals
of the Ascite family. Cellulose cannot be digested by the human body, however,
animals, in particular ruminants, can digest cellulose. It is also water insoluble.
(Viahakha 2012).
The word cellulose was first coined by the French chemist, Anselme Payen in
1838, who also was the first to identify the molecule as a fibrous component of
plant cell. Earlier works had made mention of acid hydrolysis of a component of
plant cell (Viahakha 2012; Payen 1838). The fundamental formula of the cellu-
lose structure was established by Willstatter and Zechmeister (1913) while fur-
ther work (Irvine and Hirst 1923) resulted in the presently accepted concept of
cellulose as macromolecular. By late 1931, following the numerous various work
done on cellulose the primary structure had already been established as a linear
homopolymer of glucose residues with D configuration linked by β-(1 → 4) gly-
cosidic linkages (Perez 2005).
A healthy plant cell wall is defined by its rigidity and dynamic nature. These
two requirements are met by a mixture of cellulose and protein within the plant
cell walls with cellulose microfibrils providing the resistance against tensile
strength and allowing for cell growth and extension (Jarvis 1984). Terminal com-
plexes of cellulose synthase, 5c-diphosphate (UDP) glucose, and glucose mol-
ecules are important components of the formation and elongation of cellulose
microfibrils (Malcom 2000; Perez 2005).
4 O. Olatunji

Schematic representation of plant cell wall showing the various polysaccharide

components.

Schematic representation of cellulose chain.

1.2.2 Hemicelluloses

Another major component of plant cells is hemicelluloses which form a matrix

for the cellulose microfibrils. Hemicelluloses are made up of a variety of mole-
cules such as xyloglucans, xylans, mannans, and β(1-3)-β(1-4)-glucans (Chanzy
1990; Viahakha 2012; Perez 2005) forming a matrix around the cellulose microfi-
brils. They are usually molecularly bonded to the cellulose microfibrils via forces
such as hydrogen bonds, van der Waals forces, and other molecular interactions.
Hemicelluloses also serve other functions such as cell signaling or acting as
reserves for metabolism.
While cellulose is strong and relatively chemically stable straight chain crystal-
line polysaccharide, hemicelluloses have an amorphous branched structure and lit-
tle mechanical strength. They also have a more random nature with shorter chain.
Hemicelluloses make up about 20–30 % of dry plant biomass. The industrial sig-
nificance of hemicelluloses lies in their potential to be hydrolyzed into ferment-
able sugars for applications such as ethanol production. However, a limitation in
1  Classification of Natural Polymers 5

this application is that other than glucose hemicelluloses typically consist of four
other sugars which include arabinose, galactose, xylose, and mannose. In addi-
tion to this it also contains other molecules such as acetic, glucuronic, and feru-
lic acids. This poses a limitation because fermentation of such a wide range of
substances is relatively more complex than fermentation of, for example, cellulose
(Wyman 2005).

1.2.3 Lignin

While cellulose is regarded as the most widely abundant natural polymer and
indeed the most abundant natural resource, lignin is the most abundant aromatic
polymer in nature and the next most abundant polymer. Lignin comes from the
Latin word lignum, meaning wood. Lignin was first referred to as a constituent of
wood by Ansleme Payen in 1838 as the carbon substance acting as the matrix in
wood composite embedding cellulose in wood. Later in 1865 this matrix was iden-
tified as lignin by Schulze.
Synthesis of lignin is as a result of the free radical polymerization of alco-
hols of para-hydroxy cinamic acid (Perez 2005). Like cellulose it also plays a
role in the cell structure of mainly vascular plants. Lignins are heteropolymers
with rather complex structures. These hydrophobic polymers exist in plant cell
walls providing the matrix that binds the cellulose microfibrils and other compo-
nents of the cell walls, thus providing biomechanical strength and rigidity. They
are responsible for the upright growth of plants (Wainwright 1982; Ralph 2004).
Some studies have also discovered presence of lignin in other nonvascular plants
(Martone 2009). It is believed that when plants evolved from aquatic to terres-
trial habitat about 475 million years ago, the formation of lignified cell walls was
a major structural evolution (Martone 2009; Kendrick 1997; Peter 2007; Boyce
2004).
Lignin is formed within the spaces existing around the cellulose microfibrils in
the final stage of cell differentiation in plant cell walls, thus forming a lignocellu-
loses matrix which contributes to the strength of the plant (Perez 2005).
Lignin is generally viewed as a waste material from industrial processes such as
pulp and paper production and ethanol production from lignocelluloses biomass. It
makes up about 20–305 % of cellulosic biomass. It is considered as non-fermenta-
ble, however, it is useful as a boiling fuel (Wyman 2005). On average, between 40
and 50 million tons of lignin is produced as a waste by-product from the pulp and
paper industry (Sakakibara 1991; Cotana 2014).
6 O. Olatunji

Structure of lignin and other wood constituents (Sourced from Adler (1977) with
permission license number 3633070804725).
Lignin makes up between 18 and 25 % of wood with the remaining constituents
being cellulose and hemicelluloses forming a matrix within the xylem (Brostow
2010). Lignin is present in the plant cell wall, the extracellular matrix that surrounds
the plant cell providing rigidity and support characteristics of plants (Brostow 2010).
To date the precise structure of native lignin is yet to be known and the struc-
ture of a particular lignin varies with source and extraction method. However, it is
known that it contains mainly methoxyl groups, phenolic hydroxyl groups, and a
few thermal aldehyde groups approximately in the following proportions: carbonyl
10–15 %, benzyl alcohol 15–20 %, phenolic hydroxyl 15–30 %, and methoxyl
92–96 % (Froass et al. 1996; Adler 1977).
Other than its structural role, lignin is also significant for water and nutrient
transportation within the plant and prevents the penetration of destructive enzymes
thereby preventing degradation (Sarkanen 1971; Sjöström 1993).

1.3 Pectin

Pectin refers to a complex group of molecules with a framework of mainly α-d-

(1-4_ galacturonan with intermittent units of α-l-(1-2)rhamnose. It belongs to the
class of gel forming polysaccharides alongside others such as agar and mucopol-
ysaccharides. Pectin is present in the primary cell wall of plants alongside other
components such as cellulose, hemicelluloses, and lignin. It makes up to 35 % of
1  Classification of Natural Polymers 7

the dry weight of the cell walls of dicotyledon higher plants. It constitutes less
proportion and is of different forms in monocotyledon plants. Pectin acts as a
structural and developmental polysaccharide in plants and also contributes its ion
exchange capacity, thus regulating the movement of ions and the pH of the plant
cell wall (Perez 2005; Jarvis 1984).

1.3.1 Starch (Amylose and Amylopectin)

Starch in its pure form is an odorless, tasteless white powder. It is a polysaccharide

that consists of two types of molecules; amylose and amylopectin. The concentra-
tion of each varies with the source and type of starch, however, it is usually around
20–25 % w/w amylose and 75–80 % amylopectin.
Starch is generally insoluble in water and alcohol; however, in the presence of
heat and water it can be irreversibly dissolved in water by the process known as
gelatinization. Starch is used in a variety of industrial applications, mainly adhe-
sives, paper, and clothing. The application of starch for various purposes dates as
far back as 700 A.D. when it was applied as cosmetic creams, food thickener, and
in paper production.
Amylose is a water soluble polysaccharide made up of (1-4)-α-d linked poly-
glucan in a wobbled helix configuration (Kajiwara 2005), while amylopectin takes
a branched form with branching occurring after every 28–30 glucose unit. The
branched configuration of amylopectin relative to amylase makes it more suscepti-
ble to hydrolysis and degradation as it has more regions exposed.
Despite the variation in the composition of amylase and amylopectin for differ-
ent types and sources of starch, the observed microstructure of starch granules is
almost identical for all types of starch (Burchard 2005).

1.3.2 Glycogen

Glycogen is another type of storage polysaccharide. It is similarly highly branched

and compact like other storage polysaccharides such as amylopectin (Yui 2005)
except with more branching and compactness. Glycogen exists in the cytoplasm
of animal cells where it serves as the main storage form for glucose. Albeit very
significant for body metabolism, glycogen has no industrial application and is only
mentioned here for completeness.

1.3.3 Chitin

Chitin is a highly hydrophobic linear polysaccharide of animal origin containing

amino and acetyl groups within its unit. It is insoluble in water and other organic
8 O. Olatunji

solvent, it is however soluble in specialized solvents such as chloroalcohols in

conjugation with aqueous solutions of mineral acids, hexafluoro-isopropanol, and
dimethylacetamide containing 5 % lithium chloride. It is another abundantly avail-
able structural polysaccharide in nature, present in the exoskeleton of invertebrates
such as insects, crustaceans, and other organisms including in the mycelia and
spore of fungi (Kokate 2003; Viahakha 2012). Chitin is similar in structure to cel-
lulose except for the hydroxyl groups contained within the cellulose chain that are
substituted with an acetamido group (Viahakha 2012).
Unlike most natural polymers that are either neutral or acid in nature, chitin
(as well as chitosan) is alkali in nature. This gives it some desirable properties for
various applications such as film and gel forming ability, chelation of metal ions,
and formation of polyoxysalts (Sharma et al. 2011). Chitin is especially applied
in biotechnology in the modified form of chitosan which is obtained from the
deacetylation of chitin. Chitosan is widely applied in transdermal drug delivery,
particularly for its mucoadhesive, reactive, and mechanical property, for its ten-
dency to be insoluble in neutral and alkali environment, and its solubility in acidic
environment which makes it attractive in controlled delivery (Sharma et al. 2011;
Kajiwara 2005).

1.3.4 Hyaluronic Acid

Hyaluronic acid is an example of a glycoprotein, also known as mucopolysac-

charides or mucins. It is also one of the few polysaccharides found in the tissue
of vertebrates and more abundantly in young embryo; another example of such
is heparin. These are polysaccharides bound to proteins in a covalent bond. Other
types include proteoglycans. Hyaluronic acid or hyaluronan that plays a signifi-
cant role in tissue development and cell proliferation (Guizzardi et al. 2013) is
a straight chain polysaccharide with a molecular mass of about 7 × 106 g/mol,
usually strongly attached to proteins in a hydrogen bond similar to that of water,
thus making its extraction and isolation rather onerous. Nonetheless, pure hya-
luronic acid has been isolated from sources such as cord bovine vitreous humor
and rooster combs and bacteria streptococcus zooepidemicus (Burchard 2005).
It is useful for certain biomedical applications; for instance, in combination with
alginate it is used in surgical applications for wound healing (Taravel et al. 2005;
Oerther et al. 1999).

1.3.5 Alginate

Alginate is a long chain hydrophilic polymer sourced from seaweeds, where it

exists within the cell walls providing flexibility and strength. It has been in use as
food as far back as 600 B.C. However, it was not until 1896 that the purified form
1  Classification of Natural Polymers 9

of alginate was extracted from seaweed by Akrefting. By 1929 alginate became a

commercialized product with the company Kelco being the first to commercialize
it as a stabilizing agent in ice cream (Sabra and Deckwer 2005).
It usually exists in association with other cations, mainly sodium and cal-
cium as sodium alginate and calcium alginate. The cations attached to the algi-
nate have an effect on its properties. The properties of the alginate also depend
on the species of algae, which is mainly Laminaria hyperborean, Macrocystis
pyrifera, Laminaria digitat, and Ascophyllum nodosum. Bacteria of the species
Pseudomonas and Azotobacter also produce alginate-like polymeric materials.
(Sabra and Deckwer 2005) Alginic acid serves diverse biological functions and
has various industrial applications as a stabilizing agent, drug carrier, voscosifier,
and as binding agent (Sharma et al. 2011; Sabra and Deckwer 2005). It is also
used in combination with other polymers such as chitosan and hyaluronic acid to
serve more varied functions (Taravel et al. 2005; Oerther et al. 1999).
Further details on the structures and functions of various polysaccharides can
be found in (Dumitriu 2005). Details provided here are to provide sufficient under-
standing of the various types of polysaccharides. Further chapter looks at their
applications in various industries.

1.4 Proteins

The previous sections have summarized the important roles that polysaccharides
play in plants. Proteins are also an integral part of the plant cell wall serving both
structural and functional molecules. They determine the functionality and specific-
ity of an organism (Perez 2005).
Proteins are made up of amino acid groups and sometimes other groups joined
together by amide bonds, also known as peptide bonds. Proteins can be classified
with regard to their shape, size, solubility, composition, and function.
Globular and fibrous proteins are the two types of proteins based on shape and
size. Globular proteins are water soluble types which are rather fragile in nature.
Antibodies, enzymes, and hormones are typical examples of globular proteins.
Fibrous proteins are tougher water insoluble proteins. These are usually proteins
found in structural tissues such as hair, nails, and skin.
Proteins can also be classified based on their solubility as simple, compound,
and derived proteins. Simple proteins are those which when hydrolyzed produce
amino acids only. These protein also have subcategories, which are albumins,
globins prolamins, glutelins, histones, prolamins, and abuminoids. Compound pro-
teins, also known as conjugate proteins, are a combination of simple proteins and
prosthetic groups. Conjugate proteins are of various types depending on the pros-
thetic group attached. These could be nucleoproteins lipoproteins, glycoproteins,
mucoproteins, phosphoproteins, metalloproteins, or chromoproteins.
Derived proteins are those derived from complete or partial acidic alkali or
enzymatic hydrolysis of simple or conjugate proteins. These derived proteins
10 O. Olatunji

could be either primary or secondary derived proteins. Primary derived pro-

teins are proteans, metaproteins, and coagulated proteins derived from partial
hydrolysis of the protein molecule where very little or no peptide bonds are bro-
ken. Secondary proteins are a result of more pronounced cleavage of the peptide
bonds through hydrolysis. The main types are proteoses, peptones, and peptides.
Proteins are also classified based on their functions as catalytic, protective regula-
tory, storage, transport, toxic, exotic, contractile, secretary, and structural proteins.
Catalytic, regulatory, and protective proteins are enzymes, hormones, and antibod-
ies respectively.
The following sections describe a few common proteins that are commonly
applied in industries. These include silk fibroin, silk sericin, zein, collagen, gela-
tine, casein, wheat gluten, and soy protein.

1.4.1 Silk Fibroin

Silk fibroin is a fibrous protein found in silkworms, particularly the bombyx mori,
a domestic insect of the Bombycide family. It is semicrystalline in nature with its
main amino acid contents being tyrosine, glycine serine, and alanine. Silk fibroin
makes up about 75–83 % of silk fibers with the rest of the silk fiber being made
up of sericin, wax, and other components such as hydrocarbons. Like other silks,
the silk fibroin is attractive for biomedical application due to its nontoxic, biode-
gradable, and biocompatible nature. In addition, the silk fibroin shows desirable
mechanical and chemical properties making it an excellent fiber for a variety of
applications such as food additives, cosmetics, matrix for transdermal drug deliv-
ery, scaffolds, and fibers (Prasong and Yaowalak 2009; Sharma et al. 2011; Taddei
2006; Min 2004). The silk fibroin is very versatile and can be prepared into vari-
ous forms such as gels, films, fiber, and powder (Park 2004). The amount of silk
fibroin obtained from a particular insect is affected by the nutritional intake and
environmental conditions such that these insects can be cultivated for the purpose
of producing the desired quantity and quality of silk fibroin.

1.4.2 Silk Sericin

Silk sericin is a globular, gumming protein present in the silkworm bombyx mori
alongside silk fibroin where it makes up about 17–25 % of the silk fiber. Silk
sericin is insoluble in cold water but will easily disperse in hot water (Kaewkorn
2013). Although it is most often discarded as a waste by-product of silk fibroin
production, silk sericin has found potential application in biomedicine due to its
gel forming property and its role in films and scaffolds for cosmetics and pharma-
ceutical applications. It is particularly attractive for biological application due to
the fact that it does not cause any immunological responses (Aramwit et al. 2012).
1  Classification of Natural Polymers 11

Treatment of colon cancer and anti-aging agent in cosmetics are some of the
potential applications of silk sericin in industry (Kaewkorn 2013; Kitisin 2013).

1.4.3 Zein

A by-product of corn processing, zein is a hydrophobic prolamin protein with

thermoplastic property. It is soluble in alcohol and has good film forming proper-
ties albeit forming rather brittle films; the film property can be improved through
use of other additives and by maintaining the right operating conditions (Guo
2012). It has potential for application as films and coatings in food and pharma-
ceuticals (Sharma et al. 2011; Elisangela 2007).

1.4.4 Wheat Gluten

Gluten is a by-product from processing of starch present in wheat flour (Tanada-

Palmu 2003). It contains two prolamin proteins, gliadin a monomeric polypeptide
soluble in dilute salt and glutenin a polymer complex soluble in acidic solutions
(Waga 2004). Although in the wheat plant these proteins serve mainly as storage
protein, gluten has unique viscoelastic properties which make it commercially
attractive in structural applications such as film forming and bread making. Wheat
gluten also contains other proteins, such as albumins and globulins, which serve
mainly biological purposes as catalysts and regulators (Waga 2004). The film
forming ability of wheat gluten can be modified through addition of plasticizer
such as glycerol (Tanada-palmu 2000) or varying the pH (Herald 1995).

1.4.5 Collagen

Collagen is the most abundant protein in mammals making up about 25 % of the
dry mass. It is a structural protein made of three polypeptide chains folded into
a triple helix structure usually produced by fibroblast cells. Due to its biodegrada-
bility, biocompatibility, availability, and versatility, collagen is widely applied in
biomedicine, pharmaceutics, and cosmetics. It is found in tissues such as muscles,
skin, and bone where it provides strength and flexibility. Its industrial application
includes use as scaffold and injectable (Parenteau-Bareil 2010). Collagen type var-
ies from source to source and also within sources, with the most common type
used in industries being type 1 collagen. Other types are listed in Table 1.2.
12 O. Olatunji

Table 1.2  Collagen type, forms, and distribution

Type Molecular formula Polymerized form Tissue distribution
Fibril—forming I [αl(I)]2α2(I) Fibril Bone, skin, tendons,
(fibrillar) ligaments, cornea
(represent 90 % of
total collagen of the
hitman body)
II [αl(n)]3 Fibril Cartilage,
­intervertebrate disk,
notochord, vitreous
humor in the eye
III [αl(III)]3 Fibril Skin, blood vessels
V [αl(V)]2α2(V) and Fibril (assemble with Idem as type I
αl(V)α2(V)α3(V) type I)
XI αl(XI)α2(XI)α3(XI) Fibril (assemble with Idem as type II
type II)
Fibril—associated IX α1(IX)α2(IX) Lateral association Cartilage
α3(IX) with type II fibril
XII [αl(XII)]3 Lateral association Tendons, ligaments
with type I fibril
Network—forming IV [αl(IV)]2α2(IV) Sheet-like network Basal lamina
VII [αl(VII)]3 Anchoring fibrils Beneath stratified
squamous epithelia
Source Parenteau-Bareil (2010) reproduced under creative commons attribution license

Schematics representing (a) a segment of a triple helix collagen chain, (b) collagen
molecules, (c) collagen fibril made up of collagen molecules, (d) Collagen fibril
aggregates forming collagen fiber. (Reproduced from Parenteau-Bareil (2010)
under creative commons attribution license.)
1  Classification of Natural Polymers 13

1.4.6 Gelatine

Gelatine is a derived protein; it is the partially hydrolyzed form of collagen

extracted from tissues such as bones and skins of animals through thermal hydrol-
ysis using either an acid or alkali (Zhang 2011). There is also growing interest
in extraction of gelatine from the scales of fish (Olatunji et al. 2014) and insects
(Mariod and Adam 2013) as potential preferred alternatives to mammalian
sourced gelatin. It is a mixture of polypeptides and proteins formed as a result
of irreversible hydrolysis of collagen, which results in the unfolding of the α tri-
ple helix structure by partially breaking some of the hydrogen bonds between the
inter wound polypeptide chains. Gelatin is of two types, type A which is gela-
tine obtained through acid hydrolysis and type B obtained through basic (alkali)
hydrolysis (Mariod and Adam 2013). The properties of gelatine depend on the
source and extraction method; for instance, studies have shown that gelatine from
insects have properties that are different from commercial gelatine (Abdelfadeel
2012). Studies also show that gelatine from different fishes and their parts also dif-
fer (Koli et al. 2012). Gelatin is widely applied in foods, pharmaceutics, and cos-
metics for its viscoelastic properties to act as gelling agent, thickener, or stabilizer.

1.5 Polyester

The main known polyesters in nature are cutin, suberin, and polyhydroxyalkanoates.

1.5.1 Cutin

It is a complex combination of nonpolar lipids which form part of the waxy layer that
envelopes the plant on the outermost layer, protecting it against water loss to the envi-
ronment. This plant outermost layer is referred to as cuticle; it is the structure thought
to be a major enabler of plant evolution from water to dry land due to the enhanced
water retention capacity it provides. The discovery of natural polyester from plant
cuticle came later than that of polysaccharides and proteins (Holloway 1982).

1.5.2 Suberin

Suberin is synthesized within the extracellular matrix of mainly the root tissue. It
plays a similar role as cutin of protecting the root tissue against water loss. It is
commonly used industrially as the main constituent of cork.
14 O. Olatunji

1.5.3 Polyhydroxyalkanoates

Polyhydroxyalkanoates are complexes found in bacteria, however, efforts are

being made to synthesize it in plants, particulary in the leaves (Nawrath and
Poirier 2008).

1.6 Polynucleotides

Polynucleotides are mainly ribonucleic acid (RNA) and deoxyribonucleic acid

(DNA) which serve as the building blocks of life that make up the instructions
necessary for a cell to perform its function. Polynucleotides in industry serve
biomedical purposes such as gene therapy and DNA sequencing (Manavbasi and
Suleymanoglu 2007; Templeton 2002; Ulrich 2002). Polynucleotide structure con-
sists of 13 or more nucleotide monomers joined together to form a chain. DNA for
example is made up of two chains of polynucleotides folded in a double helix. The
sequence of the nucleotides determines the instruction for the particular cell.

1.7 Polyisoprenes

Polyisoprenes are natural rubbers with thermosetting properties (Tanaka

2001). Polyisoprenes are classified into two types, cis and trans, also known as
Z-polyisoprene and E-polyisoprene. The type of polyisoprene formed is deter-
mined by the isoprene unit present and the two forms have different proper-
ties. The cis-polyisoprene is more widely available as it is produced in over 200
latex producing higher plants, particularly the rubber tree (hevea brasiliensis),
which serves as the main commercial source of polyisoprene due to the high
polyisoprene yield and the desired mechanical properties of the product. Albeit
much fewer in existence, plants producing the trans polyisoprene include bal-
ata (Minusops balata) and Gutta percha (Palaquium gutta and Eucommia ulmo-
ides (Bamba et al. 2002; Backhaus 1985; Hendricks et al. 1946). The desired
properties of trans isoprene include rigidity, insulation properties, extremely
low coefficient of thermal expansion/contraction, and alkali and acid resistance
(Asawatreratanakul et al. 2003).

1.8 Conclusion

Some natural polymers have been replicated in the laboratory. This is done in
some cases to reduce the chances of impurities or undesired components that
might be difficult to separate while extracting the desired polymer from its bulk
1  Classification of Natural Polymers 15

form. For example, use of synthetic polyisoprene in place of natural polyisoprene

is more common in industry today as the polyisoprene produced by plants such as
rubber plant is cis-polyisoprene, whereas trans polyisoprene has more desirable
properties for commercial application (Chen et al. 2012).

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Chapter 2
Processing and Characterization of Natural
Polymers

Ololade Olatunji and Olsson Richard

2.1 Introduction

Polymer processing involves two main aspects, processing of polymers into forms
for further processing as powders and pellets and processing of polymers into fin-
ished products of desired geometry such as scaffolds, microneedles, and films for
food packaging. The former involves techniques such as extrusion and blending,
while the latter could involve processes such as injection molding or film casting.
Such will be discussed in this chapter. Furthermore to determine the usefulness
and for quality assurance and safety, it is necessary to characterize polymers to
determine properties such as mechanical strength, thermal conductivity, micro-
structure, and density. For such purpose techniques such as Fourier transform
infrared spectroscopy, transmission electron microscopy, differential scanning
calorimetry, and thermogravimetry analysis have been developed and are widely
applied in characterization of polymers.
Many processing techniques applied for the industrial synthetic polymers are
applicable to natural polymers, however, in several cases certain limitations exist
which limit the applicability of some of the conventional polymer processing tech-
niques to natural polymers. Measures have been taken by researchers to address
such limitations and/or modify the polymer processing technique to suit natural
polymers. For example, starch is plasticized to form thermoplastic starch (Nafchi
et al. 2013) which can be processed using extrusion molding, a process typically
applied to thermoplastics.

O. Olatunji (*) 
Chemical Engineering Department, University of Lagos, Akoka, Lagos, Nigeria
e-mail: Lolakinola@gmail.com
O. Richard 
Fibre and Polymer Technology-Polymeric Materials, KTH Royal Institute of Technology,
Stockholm, Sweden

© Springer International Publishing Switzerland 2016 19

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_2
20 O. Olatunji and O. Richard

Proper characterization aids in the selection of polymers for specific applica-

tion such that the best suited polymer or combination of polymers can be selected.
It is desired that the typical processes used in industry for processing of synthetic
polymers to be adoptable for natural polymers in order to save costs and for con-
venience. In this chapter we also look at processing of natural polymers into com-
posites and blend. This extends to combination of natural and synthetic polymers.
We look at the role of natural polymers in composites containing either natural
or synthetic polymers as matrices. Typical characterization methods which are
applied in industry and how they are applied for characterization of natural poly-
mers are discussed.

2.2 Blends and Composites

Blends and composites are a good means of obtaining broader usability from poly-
mers either as matrix or fillers. Composites have been defined as a combination
of two or more elements with distinct identity and properties bonded to form a
multiphase multicomponent system, while the component elements maintain their
physical and chemical identities. A composite is made up of a polymer as a matrix
and a filler, where the filler could be a fiber, flake, or a woven fabric which could
be a ceramic, metal, or polymer element. Polymers can therefore play the role
of a filler or matrix in composites. The need for such systems is in the desire for
physical and/or physicochemical parameters which cannot be met by other simple
mono-component synthetic or natural materials (Cazacu and Popa 2005).
Composites can be made up of both synthetic and natural polymers. The blend-
ing of both natural and synthetic polymers yields a new breed of materials with
more varied properties for broader applications. Composites based on natural pol-
ymers have gained increasing attention as over the years largely due to the fact
that the production of synthetic polymers, albeit involving advantages such as con-
sistency of product and ease of production, have raised environmental concerns
due to their nonbiodegradability and potential toxicity.
Blends are formed when two or more polymers are physically mixed either in
the molten state or dissolved in appropriate solvent. Polymer blends obtained from
mixing of polymers can be of various forms such as miscible one phase, miscible
separated phase, compatible, incompatible, alloys, interpenetrating and semi-inter-
penetration polymer networks, or molecular composites. The two main classifica-
tions of polymer blends are either as compatible or incompatible blends.
Incompatible blends are immiscible blends where the separate phases are well
defined. These blends generally have poor mechanical properties. Compatible
blends are those blends which form a single phase where different components
cannot be separately identified morphologically. These types of polymer blends
are more likely to attain superior mechanical properties than the component poly-
mers. Incompatible blends are more common than compatible polymer blends.
2  Processing and Characterization of Natural Polymers 21

Composites exist in nature in the form of wood and bones. Wood, for example,
is a good representation of polymer composite. The hemicellulose and lignin act
as the polymer matrix component, while the cellulose fibers act as the filler com-
ponents (Freudenberg 1932; Lee et al. 2014). The interactions between the hydro-
phobic lignin and hydrophilic cellulose components are thought to be due to one
ester and one ether linkage forming a lignin cellulose complex (LCC) (Rozmarin
1984), which acts as a compatibilization agent thought to be responsible for the
peculiar structural stability of wood (Takase et al. 1989). Understanding of natu-
rally existing composites has contributed to the development of novel composites
with improved properties.
Man-made composites have been in existence since 500 BC where pitch was
used by the middle easterners as binders, papyrus, and reeds in building boats.
The Europeans, Asians, and Americans are also reported to have used laminated
wood veneers as decorations as far back as first century AD. Shellac resin-based
laminates have also been used by the Indians for over 300 years, while evidence
of laminated wood is seen in Thebes dating as far back as 1500 BC (Cazacu and
Popa 2005; Lee 1989).
Methods employed in formation of blends and composites include hand lay-up,
low-pressure injection molding, compression, molding, extrusion, centrifugal cast-
ing, spray-up, reinforced reaction injection rolling, filament winding and pultru-
sion methods (Cazacu and Popa 2005; Kulshreshtha 2002).

2.2.1 Compatibilization

The compatibility of polymer blends can be significantly improved by the pres-

ence of specific interactions such as hydrogen bonding (Cao et al. 1989) elec-
tron-donor and electron-acceptor complexation (Simmons and Eisenberg 1986)
and ion–ion pairing (Simmons and Eisenberg 1986; Cazacu and Popa 2005). The
properties of a polymer blend are dependent of the properties of individual compo-
nents. These properties can be improved by modifying the interfacial and superfi-
cial properties of the components. This process is referred to as compatibilization.
Compatibilization can be achieved by the use of additives known as compati-
bilizing agents. Compatibilization is also done by using a graft copolymer of the
natural polymer which is miscible with each of the components of the polymer
blend. This is reactive compatibilization and is chemically formed during mixing.
Chemically modifying the natural or synthetic polymers such that certain func-
tional groups are formed on the polymers, thus improving interactions between the
components of the polymer blends. Copolymerization, i.e., forming polymers from
more than one monomer unit, is also a method of compatibilization as the different
monomer units result in interactions which may improve miscibility.
Silanes such as amino silanes, aminopropyltriethoxysilane, glycidoxypropyl-
trimethoxysilane (Tran et al. 2014) and methacrylopropyltrimethoxysilane (Salon
et al. 2005), and isocyanates can also be used alongside or in place of MAPP.
22 O. Olatunji and O. Richard

The mechanism of compatibilization involves a silanol group (Si–OH) form-

ing between the silane and the water molecule on the cellulose. This then forms
a covalent or hydrogen bond with the cellulose (Xie et al. 2010). Silane has also
been used as compatibilizer in cellulose/low-density polyethylene (LDPE) com-
posites. Pre-impregnated cellulose fibers in LDPE dissolved in xylene solu-
tion yielded composites which show up to 50 % increase in mechanical strength
(Herrera-Franco and Agular-Vega 1997).
In one innovative approach degraded LDPE is used as a compatibilizer for
LDPE–wood composites (Ndlovu et al. 2013). As the LDPE degrade they form
functional groups which make them applicable as compatibilizers. Although the
degraded LDPE does not increase the thermal stability, significant improvement in
the mechanical and viscoelastic properties of the LDPE–wood composite can be
achieved using the degraded LDPE as compatibilizer. Such processing techniques
allow for utilization of partially degraded LDPE which could be in the form of
recycled LDPE contributing toward waste recycling. Some detailed examples of
compatibilizers used for producing composites of synthetic and natural polymers
can be found in (Cazacu and Popa 2005). Some of which are listed in Table 2.1.

2.2.2 Blending of Natural Polymers with Synthetic Polymers

The mixing of natural and synthetic polymers allows for the combination of the
desirable high-performance mechanical properties, consistency, and water resist-
ance property of synthetic properties with the low cost, biodegradability, multi-
functionality, and biocompatibility of natural polymers. This leads to achieving
new materials with more varied physical and physicochemical properties for
broader applications. The main aims of mixing natural and synthetic polymers
are either to reduce cost, improve performance, or tune specific properties such as
biodegradability.
Blending of polymers allows the possibility of mixing inexpensive and rela-
tively abundant polymers with expensive ones using low-cost mixing meth-
ods, thus reducing the cost of the polymer while still attaining high performance
required. The presence of natural polymers within synthetic polymer systems also
speed up the process of biodegradation. The degradation of the blend or composite
begins with the degradation of the natural polymer component within the material
which results in increasing the surface area available for water, photo, chemical,
and microbial action. This is due to the degradation of the natural polymer within
the material leaving behind spaces between the fragments of the material making
it more susceptible to degradation (Cazacu and Popa 2005). Figure 2.1 shows a
sketch of possible route for degradation of natural polymer composites.
Lignocellulose-based biomass is used in combination with synthetic polymers
as they are widely available. Lignocellulose deposited to the biosphere annually
is reported to be about 200 billion tons. This includes lignocellulose from wood
waste, e.g., furniture and construction industry, agro wastes of plants, waste from
2  Processing and Characterization of Natural Polymers 23

Table 2.1  Natural/synthetic composites and compatibilizers

Synthetic polymer Natural polymer Compatibilizer Processing Reference
technique
Polypropylene Sawdust Maleic anhydride Extrusion Cazacu and Popa
(2005)
Polypropylene Wood fibers Ethylene–propyl- Injection forming Cazacu and Popa
ene or ethyl- (2005)
ene–propylidene
copolymer
Maleate
polypropylene
Calcium stearate
Low density Lignocellulosic Ionomer Extrusion Cazacu and Popa
polyethylene fibers polyethylene Injection (2005)
Sawdust Maleate
polypropylene
Low molecu-
lar weight
polypropylnene
Maleic anhydride
Polyurethane Mechanical pulp Isocyanates Pressing Cazacu and Popa
(2005)
Phenol Lignocellulose Chemical modi- Pressing Cazacu and Popa
formaldehyde fied fibers (2005)
Polyester +  Wood fibers Phenol resins Pressing Cazacu and Popa
PE + PP (2005)
Carboxylated Natural Rubber Maleic anhy- Roll milling Onyeagoro
Nitrile Rubber dride grafted (2013)
polyisoprene
epoxy resin
Chlorinated Natural Rubber Maleic anhydrided Thermal mixing Sirisinha et al.
Polyethylene grafted ethyl- followed by roll (2004)
ene propylene milling
diene rubber
EPDM-g-MA
Carboxylated Natural rubber Bis(disopropyl) Thermal mixing Naskar et al.
nitrile rubber thiophosphoryl followed by roll (2001)
polysulphides milling
Poly(lactic acid) Natural rubber Poly(lactic acid)- Chumeka et al.
natural rubber tri (2014)
block copolymer

pulp and paper industries (Cazacu and Popa 2005). This is even more than the
quantity of synthetic polymers produced every year which is estimated at 150 mil-
lion tons per year.
The main challenges in blending natural polymers such as lignocellulose
with synthetic polymers lie in the hydrophilic nature of natural polymers such
as polysaccharides and the hydrophobic nature of synthetic polymers such as
24 O. Olatunji and O. Richard

Fig. 2.1  Degradation of natural and synthetic polymers

polyethylene. The polarity leading to intermolecular attraction between the natural

polymer but poor adhesion between the natural polymer and the synthetic polymer
leading to poor wettability and dispersion. An advantage of natural polymers is the
presence of many functional groups such as hydroxyl, ester, and carbonyl groups
(Rozmarin 1984). This makes it possible for them to be modified for desired func-
tionality and to improve compatibility with synthetic polymers, thus forming
blends and composites of high performance.
Natural polymers can be blended with synthetic polymers either as fillers, rein-
forcement fibers, mixing components, or grafted copolymers for compatibility.
Figure 2.2 shows some materials obtainable from mixing of natural and synthetic
polymers and some example applications summarized from various texts (Yeh
1995; Garg and Jana 2007; Cazacu and Popa 2005).
Incorporation of natural polymers within synthetic polymer matrices can be
done through impregnation of the natural polymer component within the mono-
mer units such as styrene, vinyl chloride or methyl acrylate, resins such as epoxy
or polystyrene or within polymer–monomer systems such as styrene–polyester
resin or methyl methacrylate–polyester resin–styrene systems, followed by polym-
erization. This impregnation allows for strong interaction between the functional
groups and components of the natural polymer and the impregnation agent.
Another means of incorporating natural polymers with synthetic polymers is
through compounding. This involves mechanical mixing of the natural polymer
with the synthetic polymer either in the melt state followed by extrusion and ther-
moforming or at room temperature. Polypropylene, polystyrene, and polyethylene
are the most common synthetic polymers blended with natural polymers.
TPS blended with LDPE and linear low-density polyethylene (LLDPE) are
formed in at twin screw extruder using PE-grafted maleic anhydride as compatibi-
lizer. Despite the reduction in tensile strength and elongation from 18 to 10.5 MPa
and 340–200 % as the TPS content increased from 5 to 20 % (Sabetzadeh et al.
2015), the composites had sufficient thermoplastic property to be processed into
films using the conventional blowing process used for commonly used polymers in
industry. The films also had the required standard mechanical properties suitable
for packaging application according to ASTM standards.
2  Processing and Characterization of Natural Polymers 25

Natural polymers
•Cellulose
•Chitosan
•Gelatin
•Starch
•Xanthan gum Applications:
•Packaging
•Controlled drug
delivery
•wound dressing
•Food
Synthetic polymers •Engineering
(drilling)
•LDPE
•Poly(NIPAAm-coAAm)
•Hydroxyphenylpropionic acid
•Polylactic acid
•Vinyl Urethanes

Fig. 2.2  Blends of natural and synthetic polymers with example applications (arranged in order
of correspondence)

It is important to be able to process biopolymers using the common industrial

processes as this makes them more adoptable industrially without the need for
specialized equipment which could increase cost of production. It must therefore
be considered that a trade-off between the optimum performance property of the
material and the environmental friendliness should be carefully considered, while
selecting natural- and synthetic-based polymers for any industrial application.
Natural polymers are also blended with other natural polymers. This allows
a combination of their properties to obtain a fully biodegradable material with
improved properties. For example, a combination of chitosan with cellulose com-
bines the film-forming properties of chitosan with the structural strength of cel-
lulose. Such blends of natural polymers tend to be more compatible due to the
similarity in structure and hydrophilic nature.
Energy of mixing for blends and composites
It is not enough to simply mix components to obtain a composite with the expecta-
tion that it would result in a new material with desired properties. It is important
to study the particular properties of each component, the interactions between the
component, compatibility or incompatibility of the components, and the long-term
stability of the produced composite. The structural and molecular characterization
of the composites is therefore of importance.
26 O. Olatunji and O. Richard

Detailed understanding of the structural and morphological properties of com-

ponents makes it possible to pre-evaluate the miscibility of components to form
composites thus making for easier selection processes. Such did not become possi-
ble until 1995 (Cazacu and Popa 2005). It is established that the miscibility of two
or more polymers is dependent on the free energy of mixing (Gmix).
�Gmix = �Hmix − T �Smix < 0 (2.1)
Hmix and Smix are the enthalpy and entropy variations and T is temperature. To
form a miscible blend, the Gmix must be negative (Cazacu and Popa 2005).

2.2.3 Natural Polymers as Matrix in Composites

Natural polymers are used as matrices for composites either alone or in combina-
tion with synthetic or other natural polymers. Natural polymers such as rubber,
starch, cellulose, chitosan, and gelatin are used as composite matrix in various
applications such as construction and biomedical. This could be either in their
modified form, refined form, partially isolated form, or in their raw complex form.
Although natural polymers have disadvantages such as poor consistency, high
moisture absorbance, low resistance to UV, chemical and microbial activity, they
possess advantages such as low cost, biodegradability, lightweight, versatility (due
to the fact that they can be modified into different forms based on their functional
groups) and availability, for example, lignocellulose-based waste estimated to up
to 200 billion tons annually).
Starch is a good candidate for polymer matrix, however, starch is prone to
destruction and polymerization during processing into the melt state (Bergthaller
et al. 1999). This challenge is addressed by adopting the right processing condi-
tions, using a twin screw extruder or a corotating twin screw extruder. The applica-
tion of plasticizers such as glycerol, sorbitol, urea, polyethylene glycol, poly vinyl
alcohol, and sucrose also improves the processibility of starch (Roper and Koch
1990). This results in a thermoplastic, flexible, biodegradable, hydrophilic starch
form referred to as thermoplastic starch (TPS). TPS has better thermoplasticity,
film forming, and molding properties (Cazacu and Popa 2005).
TPS starch composites incorporating natural and synthetic polymers can be
formed using industrial thermoforming methods such as extrusion and injec-
tion molding. In particular, example compounding TPS from cassava source
with synthetic polymer, LDPE significantly improves the thermal and mechani-
cal properties of TPS. Further improvement in the mechanical properties is
observed by modification into composites using cotton fibers as reinforcement
and carrageenan as gelling agent. The composite was processed using an internal
melt mixer followed by injection molding without damaging effects on the TPS
(Prachayawarakorn and Pombage 2014).
Composites of glycerol-plasticized TPS from rice starch with either cotton or
LDPE as reinforcing agents show improved tensile strength and Young’s modulus
2  Processing and Characterization of Natural Polymers 27

with the incorporation of cotton or LDPE compared to TPS only. The compatibil-
ity between TPS and LDPE is improved using either maleic anhydride polyeth-
ylene or vinyltrimethoxysilane as compatibilizing agents. The water absorption
property which is important in maintaining the stability of the material is reduced
by the inclusion of cotton and LDPE in the TPS matrix (Prachayawarakorn et al.
2010). In this case the synthetic polymer is also acting as a filler rather than
a matrix in the composite, while the natural polymer TPS acts as the matrix
component.

2.2.4 Natural Polymers as Fillers and Reinforcements

Natural polymers in their modified, refined, or complex raw form can also be
incorporated into natural or synthetic polymer matrixes. In Table 2.2 we summa-
rize some natural polymers used as filler in composites of natural and synthetic
polymers. Most of the natural fibers used as reinforcement in polymer composites
are cellulose, lignocellulose, or pectin based. They derived from sources such as
wood, cereal straw, bagasse, cotton bark, rice husks, pulp, and vegetables such as
jute, flax, sisal, hemp, and ramie (Cerqueira et al. 2011).
Cellulose is commonly used as reinforcement or fillers in natural and syn-
thetic polymer matrices as fibers, viscose, and powders or in modified forms as
esters, ethers, or grafted onto the polymer. Other than being the most abundant
polymer in nature, it offers advantages such as low cost, low density, mechani-
cal strength, ease of processing and biodegradability (Cazacu and Popa 2005).
Cellulose also tends to form better bonds with polymers, a property thought to be
due to the interaction between the –OH groups in cellulose’s anhydroglucose unit

Table 2.2  Natural polymer as matrices in composites

Natural polymer Filler/ Compatibilizer Processing Reference
matrix reinforcement method
Natural rubber Jute fiber – Roll milling Pantamanatsopa
followed by hot et al. (2014)
compression
Wheat starch Cotton fiber – Hand layup Komuraiah et al.
(2013)
Natural rubber Organophilic Epoxidized natural Internal mixer Teh et al. (2004)
layered clay rubber followed by vul-
(organoclay) canization using
conventional
sulphuric system
Natural White rice husk Poly(propylene– Internal mixer Ismail et al.
rubber/LLDPE ash ethylene–acrylic (2001)
blend acid) (PPEAA)
Rice starch Cotton fiber – Hand layup Komuraiah et al.
(2013)
28 O. Olatunji and O. Richard

and the functional groups present in the synthetic polymers. Cellulose has three
–OH groups which have different polarity and regioselectivity which attribute to
the peculiar physical properties of cellulose and its ability to form various deriva-
tives. The versatility of cellulose makes it possible to modify for various compos-
ite systems.
The poor solubility in organic solvent, low thermal stability, hydrophillicity,
and polarity of cellulose poses some challenges in application as fillers in compos-
ites. This leads to poor dispersion in melted polymer, weak interaction between the
cellulose fiber and matrix and difficulty in thermal processing. These challenges
can, however, be met by using a compatibilizer, chemical modification of the cel-
lulose, or by dissolving cellulose in a suitable solvent prior to dispersing in non-
solvent for better dispersion (Cazacu and Popa 2005).
As an example we look at natural fiber jute reinforced natural rubber.
In this case natural polymers are being used as matrix and reinforcement.
Compatibilization is achieved through coating of the jute fiber with natural rub-
ber using immersion technique. The fibers are treated with sulphuric acid to del-
ignify prior to coating. The impact of treatment of the jute fiber is compared with
untreated jute fibers and natural rubber in Fig. 2.3. In Table 2.2 we list some com-
posite systems which use natural polymers as matrices. While Table 2.3 gives
some examples of natural polymers as fillers in synthetic and natural matrices.
Polypropylene is one of the common synthetic polymers for producing cel-
lulose-reinforced composites. For this purpose maleic anhydride-grafted poly-
propylene (MAPP) is the preferred compatibilizing agent. MAPP can be bonded
covalently through esterification to the cellulose functional groups. The effective-
ness of the bonding depends on the PP chain length in the MAPP. Where short

Fig. 2.3  Stress–strain graph of HANR and DPNR-treated jute composite compared with

untreated jute composite and natural rubber (Pantamanatsopa et al. 2014) (creative commons
license)
2  Processing and Characterization of Natural Polymers 29

Table 2.3  Some examples of natural polymer fillers in synthetic and natural matrices

Natural polymer Polymer matrix Compatibilizer Processing Reference
filler method
Cotton fiber Rice starch Hand layup Komuraiah et al.
Wheat starch (2013)
Urea formal
dehyde
Plaster of paris
Sugarcane bagasse Polypropylene 10 % Sulfuric Cerqueira et al.
fiber acid, deligni- (2011)
fication and
compounding in
a thermokinetic
mixer
Sisal fiber Polylactide Bacteria nanocel- Solvent cast- Lee et al. (2012)
(PLLA) lulose coating ing followed
by injection
molding
Cellulose Fish gelatin – Solvent casting Santos et al.
(2014)

chains facilitate coupling between polar groups on cellulose and nonpolar groups
of the synthetic plastic. While longer PP chains cause steric hinderance which lim-
its the attraction between the cellulose and polymer to the superficial layer (Felix
and Gatenholm 1991; Cazacu and Popa 2005).
Composites of natural polymer blends can be produced by dissolving the fiber
and matrix material, mixing the dissolved form followed by film casting and dry-
ing. This can be achieved by either dissolving the fiber and matrix in the same
solvent, coagulating in a nonsolvent or coagulation in a vinyl solvent prior to
polymerization of the resulting gel (Nishio 1994; Cazacu and Popa 2005).

2.3 Processing Techniques

The method of processing of polymer composites depends on the factors such as

the nature of the polymer and fiber, the targeted application which could be bio-
medical applications such as wound healing and scaffold or for construction or
producing vehicle car parts. In this section we will look at some specific examples
where natural polymer has been processed into composites for various applica-
tions. In so doing we will discuss the processing techniques used to produce the
natural polymer being discussed. The processing techniques discussed here vary
from those used for engineering applications such as composites used for aircrafts
to those used in biomedical applications such as scaffolds for tissue replacement
and transdermal films for wound healing.
30 O. Olatunji and O. Richard

2.3.1 Extrusion Molding

Extrusion molding is generally used for polymers with thermoplastic properties.

The process involves melting polymers under heat and shear to achieve uniform-
ity of the polymer with or without other polymers and additives to form blends
or composites. Processing of polymers as matrixes for applications such as phar-
maceutical or engineering often require processing the polymer in its melt state to
attain uniformity and desired shape. Extrusion molding is mostly based on flow of
a molten polymer in a screw, while injection molding in addition to this involves
flow of the molten polymer into a cavity and cooling of the polymer within the
cavity. The polymer is usually introduced into the system through the hoper in the
pellet or granular form, this then forced through a screw and barrel which melts
and mixes it and then through a die where it forms into desired shape. There
usually exists a breaker plate and screen between the barrel and die to filter out
unwanted particles and achieve uniformity. This is followed by sizing and cooling
where the extruded polymer is formed into final size and cooled. The conditions
(such as temperature, pressure, speed, time) in an injection or extrusion molding
system depend on the type of polymer and other constituents of the blends (fillers,
additives, etc.). Extrusion is a very versatile process of much industrial relevance.
Typically, extrusion process is used widely in plastics industries to achieve end
products such as pipes, tubing, straws, and films for packaging. Further reading
on extrusion can be found in Seymour and Carraher (1992) and Ebewele (2000).
Figure 2.4 is a representative sketch of an extruder.
This method has been applied in various industries such as pharmaceutical
(Vervaet et al. 2008). In the pharmaceutical application, for example, where the
incorporation of drug within a polymer is required as a matrix carrier for drug
component and other additives. A hot melt extrusion process is used to achieve a
uniform blend of the drug formulation. In such applications there are usually tem-
perature restriction to prevent denaturing of the active drug ingredient such that
hot melt extrusion of pharmaceutical agents employ polymers which can be ther-
moformed at relatively low temperature which will not damage the drug ingredi-
ent. Hot melt extrusion is often preferred over other methods such as compression
molding of casting due to its continuity which makes automation more possible as
all processes (mixing, melting, and shaping) can be completed in a single equip-
ment (Repka et al. 2007; Crowley et al. 2007).
Hot melt extrusion is also preferred due to the homogeneity attainable from
the process. Examples of natural polymers which can be processed using hot melt

Fig. 2.4  Illustrative sketch of an extruder

2  Processing and Characterization of Natural Polymers 31

process include gelatin (Andreuccetti et al. 2012), starch, waxes, lipids, and deriv-
atives of cellulose such as ethyl cellulose (Vervaet et al. 2008). Often plasticizers
are used to improve the thermoplastic properties of the polymer for better thermal
processing.
Here we use an example of the preparation of gelatin-based films containing
Yucca schidigera extract using glycerol as plasticizer where extrusion molding is
applied in preparing the films (Andreuccetti et al. 2012). Glycerol concentration
varies between 0.25 and 8.75 g per 100 g of protein. When extrusion, blown extru-
sion and casting method are compared, the processing technique does affect the
properties of final film formed. The films produced by extrusion showed higher
flexibility than the blown or casted films. While the solubility of the films is not
affected by the processing method, the extrusion blown films had lower water per-
meability. It is also necessary to add water up to a moisture content of 35 % to the
gelatin-based film to further aid the extrusion process. Prior to extrusion the sam-
ples are allowed to equilibrate at 5 C and 60 % humidity for 24 h. The temperature
in the feeding zone of the extruder was 65, 100 C in the intermediate zone and
75 C at the die while the screw rotated at a speed of 47.2 rpm.
In one novel approach, conditions in an extrusion process provided the right con-
ditions (temperature and pressure) for wood to exhibit flow properties which results
in more compatible blending with engineering plastics to form better wood plastic
composites. Here the wood was first modified using phenol formaldehyde. Under
these conditions the polymers in wood, mainly lignin and carbohydrate serve as
plasticizers and binders, to give wood its thermoplastic properties making it pos-
sible for wood to be heat extruded like other engineering plastics (Miki et al. 2014).
Multilayer extrusion is also possible. This is of particular importance for mois-
ture-sensitive polymers such as starch and proteins. In this case a layer of water-
resistant polymer or other material can be coated unto the moisture-sensitive
polymer forming multiple layers of controlled thickness (Yu et al. 2006; Martin
et al. 2001; Van Tuil et al. 2000; Wang et al. 2000).

2.3.2 Injection Molding

Injection molding is also a fairly versatile process of industrial significance. It

involves conversion of thermoplastic and thermosetting polymers in the molten or
viscous state into solid finished materials. It is typically used for achieving fin-
ished products such as forks, spoons, and parts for electronics. The process gener-
ally involves heating of the polymer which is introduced in the form of pellets of
powder, followed by injection within a heated barrel and screw and then injecting
into a mold cavity and cooled under pressure to minimize shrinkage. The resulting
cooled polymer is then ejected from the unit.
Injection molding has been shown to be applicable in the biomedical area
for producing, for instance, 3D scaffolds. Scaffolds developed from cornstarch-
based polymers have been introduced using hydroxyapatite as reinforcement and
32 O. Olatunji and O. Richard

carboxylic acid-based blowing agent (Gomes et al. 2001). It is possible to achieve

3D scaffolds with complex structures and porosity, while maintaining significant
mechanical strength. Producing scaffolds using conventional injection molding
offers the possibility of achieving a reproducible method for producing biode-
gradable polymer-based scaffolds for load-bearing tissues. A review of injection
molding and its applications in drug delivery contains some natural polymer-based
polymer products of injection molding (Zema et al. 2012).
A biocomposite consisting or crayfish powder with 60 % protein and polycap-
rolactone has been used to prepare biocomposite using injection molding (Felix
et al. 2015). The plasticity of the protein was enhanced using glycerol as plasti-
cizer. The injection molding conditions such as temperature and speed were
optimized by rheometry and thermal analysis. The mechanical properties of the
crayfish powder protein were significantly enhanced to yield a composite material
with suitable mechanical properties for injection molding.

2.3.3 Solvent Casting

This is a processing method commonly used for forming polymer films. The abil-
ity of polymers to form films is important for various applications such as pack-
aging, transdermal drug delivery, and wound healing. Films may also be used as
coatings. Uniformity is key characteristics of films for any application. To achieve
consistency in film formation either from neat polymers or blends certain proce-
dures are followed. Methods for film forming include self-absorption of monolay-
ers (SAM), spin coating, thermal spraying, solvent casting, floating technique, and
Langmuir–Blodgett film forming. Most common techniques being solvent casting
and spin coating.
Here we take a case study of nanocellulose as a reinforcement in polymer com-
posite focusing on the processing techniques applied in developing such com-
posite. Gelatin from fish skin is acting as the polymer matrix, while cellulose
whiskers from cotton linter are used as the reinforcement component (Santos et al.
2014).
First water at 24 °C was used to hydrate the gelatin and glycerol using 25 wt%
glycerol concentration. The suspension was heated to 50 °C and stirred for 15 min
at this temperature. This was followed by slowly adding the cellulose whiskers,
while homogenizing at 10,000 rpm for 10 min. After the first 2 min the cellulose
was completely added. The homogenization is a mechanical method of prevent-
ing aggregation of the cellulose in the gelatin mixture. To eliminate gas bubbles,
some of which might have been formed during the homogenizing, the gelatin/
cellulose mixture was vacuum degassed using a V-700 vacuum pump at 30 mbar
for an hour. The films were formed by pouring on a glass plate and allowed to
dry at room temperature for 24 h, after which dry films are formed. The films are
detached from the glass plate and can be stored in a desiccator to maintain a con-
stant humidity (Santos et al. 2014).
2  Processing and Characterization of Natural Polymers 33

2.3.4 Spin Coating

Spin coating is a well-established technique widely used in polymer industry to

produce thin films on substrates. The typical setup includes a dispenser unit and
a spinning unit as illustrated in Fig. 2.5. The dispenser deposits a small amount of
the material which could be in the form of a neat polymer, a polymer composite
or a resin, onto the center of the substrate attached to the spinning unit. The spin-
ning unit then spins at a set speed which is usually between 1500 and 6000 rpm
depending on the requirement. This spinning motion induces a centripetal force,
which results in the material spreading to form a thin film. Excess film is spun off
the substrate. A film in the micrometer range is classified as a thin film.
The film thickness can be controlled by varying parameters such as spinning
speed, spinning time, and the fluid viscosity. This process has been employed for
coating thin films of natural polymers such as chitosan (Mironenko et al. 2014),
hyaluronic acid (Ding et al. 2012), and cellulose (Da Roz et al. 2010) for various
applications. An example is the coating of thin films of chitosan in application as
planar optical waveguides (Mironenko et al. 2014).

2.3.5 Self-assemble of Monolayers (SAM)

Although more applied to synthetic polymers, the SAM method has been used to
process cellulose into biofunctional interfaces (Yokota et al. 2008). The cellulose
maintained its biological functionality after processing by the SAM method. This
was evident by good cell proliferation and adhesion. This method involves modi-
fying the surface of a material in order to impose certain functionalities to improve
properties such as adhesion, biosensing, friction, and wetting (Chaudhury 1995).
The mechanical properties of the material such as stiffness and flexibility may be

Fig. 2.5  A commercially available spin coater Chemat precision spin from Sigma Aldrich
(image publicly available at www.sigmaaldrich.com)
34 O. Olatunji and O. Richard

desired, however, the surface properties might limit its applicability for particular
functions. Self-assembly of monolayers is applied to alter the surface properties,
while retaining the mechanical properties of the material. For instance in applica-
tions for scaffold, a polymer material may possess the required mechanical proper-
ties, however, the surface properties could limit cell adhesion and proliferation.

2.3.6 Natural Polymer Microneedles

The field of micromanufacturing has been fast expanding in the past decades. The
ability to make omicron-sized devices with precision and mass reproducible tech-
niques is of much industrial significance. This is key to designing more effective
tools for applications in biomedical, engineering, and pharmaceutical industries
for example. Natural polymers are particularly attractive for micromanufactur-
ing due to their relative low cost and ease of processing. In this section particular
focus is placed on microneedle production as example of micromanufacturing-
based devices used in biomedical applications for drug and vaccine delivery.
Microfabrication of microneedles from natural polymer generally requires
obtaining the dissolved form of the polymer such that the polymer is molded using
centrifugal micromolding followed by drying to allow the solvent evaporate leav-
ing behind a polymer which takes the shape of the mold. Silk fibroins from the
Bombyx mori silkworm have been used to fabricate fast-dissolving micronee-
dles using the centrifuge casting method (Kaplan et al. 2013; You et al. 2011). In
a typical process the silk is extracted from the Bombyx mori silkworm by boil-
ing for 30 min in aqueous solution of sodium carbonate (Na2CO3) followed by
thorough rinsing with deionized water to extract the sticky sericin proteins. This
was followed by overnight drying of the extracted fibroin. Dissolving the dried
fibroin in 9.3 M Lithium Bromide (LiBr) solution at room temperature yielded a
20 wt% solution. The LiBr was then removed from the solution through the dialy-
sis process in water for 48 h. To remove particulates and contaminants the silk
fibroin was centrifugated and microfilters yielding 8–10 wt% fibroin. Dry fibroin
is obtained through evaporation to remove water. Microneedles are fabricated from
the silk fibroin using the typical micromolding process as illustrated in Fig. 2.6,
similar methods for polymer microneedle production have been presented in other
studies (Olatunji et al. 2014). The polymer in the dissolved form is poured over a
PDMS (Polydimethyl siloxane) mold which has been prepared by either reverse
micromolding or laser drilling, under applied centrifugal force of about 2500 rpm
for 15 min, the polymer takes the shape on the PDMS as illustrated in Fig. 2.6.
The polymer is then left to dry in the mold, after which it is separated from the
mold.
Likewise fish scale biopolymers have been microfabricated into micronee-
dles using centrifuge molding (Olatunji et al. 2014). Biopolymer was extracted
from fish scale using thermal hydrolysis. The polymer was then used to produce
microneedles which were shown to have sufficient strength to penetrate into the
2  Processing and Characterization of Natural Polymers 35

Fig. 2.6  Schematics of micromolding process for silk fibroin microneedles (Kaplan et al. 2013).
Reproduced with permission License number 3623650472538

skin. Figure 2.7 shows the microneedle gradually dissolving in the skin. Such
microneedles take advantage of the fact that when in the dry form these polymers
form hard glassy material but when in contact with moisture in the skin they dis-
solve to release the active ingredients embedded within the structure.
More recently, compression molding at low temperature of about 50 °C has
been introduced for micromolding of fish scale polymer-based microneedles
with cellulose nanocomposites. The study showed that the compression mold-
ing method can be used to obtain microneedles with sharp tip by optimizing the
operating conditions for particular fish scale/nanocellulose compositions. As the
polymer films of fish scale/nanocellulose blend do not easily redissolve in water,

Fig. 2.7  Fish scale microneedles gradually dissolving in the skin (Olatunji et al. 2014)
36 O. Olatunji and O. Richard

Fig. 2.8  Spatially
discrete thermal drawing
of biodegradable polymer
microneedles (Choi et al.
2013) with permission from
Elsevier License number
3632190774292

this method offers a more ideal microfabrication to achieve microneedles from the
fish scale nanocellulose blends and similarly for other polymer blends which do
not easily dissolve in water but have limited thermoplasticity. Other novel methods
for processing biodegradable polymer microneedles make use of spatially discrete
thermal drawing (Choi et al. 2013). In this process the polymer is dispensed on a
tray followed by application of another tray such that the polymer lies between
the two plates. The plates are heated to a certain temperature depending on the
melting and transition point of the polymer. The upper plate is then moved upward
such that the polymer is pooled at a controlled speed while cooling this is illus-
trated in Fig. 2.8. The pulling results in formation of microneedles with sharp tips.
Microneedles produced from glass albeit limited to experimental applications are
produced using thermal drawing of glass micropipettes over Bunsen burner or
using a pipette puller to form glass microneedles (Olatunji et al. 2014).

2.3.7 Cellulose Nanoparticles

Reduction of particle size to the micro or nano scale could improve the functional-
ity of the polymer significantly. Many research efforts are currently being placed
on nanocellulose for production of high-performance composites. Nanocellulose
is sourced from the bottom-up approach through biosynthesis by some bacteria
such as bacteria of the Acetobacter species. Alternatively, they can be sourced
from plants through the top-down approach by disintegration of the plant matter
(Turbak et al. 1983; Herrick et al. 1983). Nanocellulose is also sourced from Algae
(Preston and Nicolai 1948) and tunicate (Belton et al. 1989; Lee et al. 2014).
Figures 2.9 and 2.10 show example of a plant and bacterial cellulose.
Magnetic decoration of cellulose nanoparticles have been used to achieve tough
membranes suitable for application in speakers’ production. Using the magnetic
decoration method, well-dispersed nanomagnets in cellulose fiber network can be
achieved leading to tough structures. Figure 2.11 shows steps in the preparation of
2  Processing and Characterization of Natural Polymers 37

Fig. 2.9  Image showing a 3-day-old culture of Acetobacter xylinum. The gel-like pellicle can be
seen in the culture. Under SEM, the pellicle appears to be made of a nanofibrillar network of cel-
lulose. Obtained from Lee et al. (2014). Reproduced under creative commons license

Fig. 2.10  Image showing the nanometre scale of a 1 wt% NFC suspension in water (Lee et al.
2014). Figures taken from Lee et al. (2012a, b). Reproduced under creative commons license

magnetic nanocomposites from decorated cellulose nanofibrils (NFC). (a) shows

structure of a softwood tissue; this is processed using high shear microfluidiza-
tion to obtain nanofibrils from the cell wall; AFM image of the cellulose nanofi-
brils. (b) Magnetic decorated nanofibrils are obtained by in situ precipitation of
magnetic ferrite nanoparticles onto the nanofibrils from metal salt solutions; SEM
image of a decorated nanofibril. (c) Further drying results in formation of mag-
netic nanocomposite hydrogel, overnight drying, and rotation on a Teflon surface
resulted in formation of hard permanently magnetized spherical beads—this is
followed by vacuum filtration of the magnetic decorated nanofibril suspension to
obtain large magnetic membranes (20 cm diameter); the image next to it shows
adaption of hybrid magnetic membranes in a thin prototype loudspeaker without
external magnet. The consecutive processing steps are indicated by the numbering
in Fig. 2.11.
38 O. Olatunji and O. Richard

Fig. 2.11  It shows steps in the preparation of magnetic nanocomposites from decorated cel-
lulose nanofibrils (NFC). a Shows structure of a softwood tissue; AFM image of the cellulose
nanofibrils. b Magnetic decorated nanofibril; SEM image of a decorated nanofibril. c Magnetic
nanocomposite hydrogel, hard permanently magnetized spherical beads—large magnetic mem-
branes (20 cm diameter); adaption of hybrid magnetic membranes in a thin prototype loud-
speaker without external magnet. Reproduced under creative commons attributed license

2.3.8 Electrospinning, Melt Spinning, and Wet Spinning

Production of microfibers from composite materials with good dispersion and

mechanical properties in a reproducible manner can be achieved using electrospin-
ning, melt spinning, and wet spinning. Figure 2.12 is a schematics of the working
principles of electrospinning and melt spinning.
A typical electrospinning process consists of a syringe attached to a syringe
pump with a pump controller, a high voltage supply, and a collector plate. The
metallic tip of the needle of the syringe is connected to the high voltage supply.
The pump pushes the polymer out of the syringe while the high voltage causes a
spinning of the polymer resulting in fibers in the nano or micro range forming on
the collector plate. The nature of the electrospun fiber obtained depends on operat-
ing conditions such as voltage, fluid properties of the polymer, nature of collec-
tor plate, flow rate, distance from collector plate, and dimensions of the needle
tip (Rojas et al. 2009). Here we use an example of electrospun nanowhiskers with
2  Processing and Characterization of Natural Polymers 39

(a)
Syringe
containing Spinneret Spun fibre
polymer solution connected to
attached to high voltage
syringe pump Collector
plate

(b)

Polymer in melt state

Spineret

Fiber is taken up
by winder and
wound into a roll

Fig. 2.12  Schematics of a electrospinning process, b melt spinning process

polystyrene shown in Fig. 2.13. Electrospinning has been applied for processing of

natural polymers such as silk fibroin (Cho et al. 2012), Chitosan (Wan et al. 2008).
Melt spinning process generally involves passing a polymer in the melt state
through multiple spinnerettes and into a series of rolls and finally winder where it
is wound up into fiber bundles (Fig. 2.12b). The main challenge in this process for
application in the processing of natural polymers lies in the thermal sensitivity of
natural polymers compared to synthetic thermoplastic polymers. Nonetheless melt
spinning has been applied to a variety of natural polymer-based materials. For
example, smooth defect-free nanocomposite fibers based on cellulose nanocrys-
tals have been achieved using melt spinning process with the inclusion of cellu-
lose acetate butyrate and triethylacetate. The spinning was done with a twin screw
micro-compounder and it was observed that increasing the cellulose nanocrys-
tal volume in the composite resulted in a fiber with better mechanical properties
(Hooshmand et al. 2014).
Additionally, shell-core structured carbon fibers containing pyrolyzed fuel oil
and natural polymer, lignin from wood have achieved using melt spinning. The
blend was spun into fibers following dissolving in tetrahydrofuran as solvent. The
blends were spun at 280 °C. The fibers showed both crystalline and amorphous
regions due to the presence of lignin, however, they possessed good mechanical
properties (modulus = 100 GPa) (Kim et al. 2015). In other studies PLA/bacteria
40 O. Olatunji and O. Richard

Fig. 2.13  SEM of electrospun PS microfibers filled with 6 % cellulose nanowhiskers in the pres-
ence of nonionic surfactant (PS:CNW:S ratio of 94:6:6) showing ribbon-shaped structures. The
operating conditions were 20 % PS in THF, Q = 0.2 mL/min, 40 kV, distance = 16 cm. Repro-
duced with permission from Rojas et al. (2009). License number 3632200995714. Original Pub-
lisher John Wiley and Sons

cellulose blends reinforced with PDLLA (poly(D, L) lactide were achieved using
melt spinning (Blaker et al. 2015).
The wet spinning process similarly involves passing molten polymer through
a spinnerette using a pump. The exiting fiber from the spinnerette in this case is
passed toa spin bath containing solvent which allows coagulation to occur. This is
then followed by further stretching, washing and drying, all in continuous stages
on a series of rolls. The fiber is finally passed into a winder where it is wound up
into a bundle. Collagen fibers have been processed using the wet spinning process
and showed better mechanical properties than thermally spun collagen (Meyer
et al. 2010).

2.4 Characterization

The structural characterization to determine the conformation of polymers such

as polysaccharides is based on understanding the characteristic energy release for
specific types of linkages which is measured by the angle of rotation about the
linkage. This is particularly effective for compounds with well-established con-
formations such as polysaccharides and oligosaccharides. For instance by having
information on the dihedral angles of rotation about the monosaccharide link-
ages in a polysaccharide or oligosaccharide chain, a detailed geometry of com-
pound can be obtained (Kijawara and Miyamoto 2007). A random conformation is
assumed, for example, for a polysaccharide showing independent rotations at each
2  Processing and Characterization of Natural Polymers 41

monosaccharide link. Interactions between and within chains limit the likelihood
of a random conformation as this allows less room for independent rotation.
Conformation is important in the functionality of the polymer. Taking a case
of cellulose and amylose, polysaccharides both made up of the same monomer
units and are both poly-d-glucans with (1→4)-α-d-Linkages. However, that of
amylose results in a wobbled helix while cellulose has a stretched zig-zag chain
conformation. This difference in conformation results in edible and soluble amyl-
ose while cellulose is inedible and water insoluble. Characterization of polymers
also help determine the crystalline or amorphous nature of a polymer. Crystalline
compounds tend to form much stronger structure. Polysaccharides rarely form
crystal structures while proteins maintain their crystal structures even in solution
(Kijawara and Miyamoto 2007).
In this section techniques such as small-angle X-ray scattering, X-ray dif-
fraction, Fourier transform infrared spectrometry and magnetic resonance are
employed.

2.4.1 Small-Angle X-ray Scattering (SAXS)

This is an X-ray-based method that is characterized by a small angle. SAXS can

produce rapid analysis of polymers such as proteins (Putnam et al. 2014) and poly-
saccharides (Kijawara and Miyamotos 2007) in solution. This process is based on
the principles of reciprocal law which relates the distance r in a real space with the
scattering vector q in a scattering space also known as the Fourier space (Kijawara
and Miyamotos 2007).
As presented by Glatter and Kratky, the electron density distribution within
the object can be determined from the scattering intensity I(q). This is done by
expressing I(q) as the Fourier transformation of the scattering angle (Eq. 2.2)
(Glatter and Kratky 1982).
ˆ∞
I(q) = V = 4πr 2 γ (r) · exp(−iq · r)dr (2.2)
0
where y(r) represents averaged product of two electron density fluctuations as a
distance r. The scattering vector is expressed as a function of the wavelength θ and
the scattering angle λ given as:
V = (4π/) sin(θ/2) (2.3)
The shape of the scattering object p(r) is characterized by the distance distribution
which is defined as:
p(r) = Vr 2 · γ (r) (2.4)
The number of electrons in the object is represented by the scattered intensity.
Maximum scattered intensity is at zero scattering angle and relates to the number
42 O. Olatunji and O. Richard

of electrons in the object. The set of relationships can then be solved by various
mathematical models presented in literature (Putnam et al. 2014; Kijawara and
Miyamoto 2007; Takeda et al. 1977). The data are then matched with existing
models of conformations to establish the true conformation of the polymer being
analyzed.
SAXS provides rapid but low-resolution structural characterization of poly-
mers; it is also used in combination with other methods. As the properties of the
X-ray being used is known, the other parameters can be calculated from the vari-
ous mathematical models that exist for SAXS profile (Putnam et al. 2014). As
an advantage SAXS is not limited to crystallized samples only and can be used
to study macromolecules in solution. This is of particular advantage for natural
polymers which do not easily crystallize. The reader is referred to other texts
(Burchard and Meuser 1993; Glatter and Kratky 1982; Kijawara and Miyamoto
2007; Putnam et al. 2014) for more details on SAXS method.

2.4.2 Nuclear Magnetic Resonance (NMR)

The assignment of specific protons or carbons to specific linkages and determina-

tion of conformation of these linkages provides more detailed information about
a material. This can be done using NMR. This is a noninvasive spectroscopic
method used for the structural analysis and conformational dynamics of polymers.
A NMR spectrometer typically consists of a magnet, a radio frequency (RF) trans-
mitter (Oscillator), and an RF detector. A sample placed between the magnets is
subjected to an RF at s known frequency. The material absorbs the RF and detec-
tor picks up the absorption of the RF at a particular frequency and the magnetic
field strength. The absorption of the RF is called resonance. A plot of the oscillator
frequency against the magnetic strength at the particular frequency provides infor-
mation on the chemical property of the material (Roberts 1959).
Despite its limitation to polymers which are mostly noncrystalline, it is rela-
tively robust as it can be used to obtain data on the conformation, stereoregular-
ity, primary and secondary structure of proteins, polysaccharides and synthetic
polymers in liquid, solid, or gel forms. NMR spectroscopy is specific, the analysis
can be directed at functional groups, main chain and side chains at specific sites.
Information on the time-dependent structure of the polymer as well as molecu-
lar motion can be obtained. When compared to other methods such as X-ray scat-
tering, NMR has a better sensitivity to microscopic structure within a short-range
order, however, on a long-range and higher order information is not well retained
and may be lost. NMR does not accurately determine spatial position of atomic
groups. NMR also takes a considerable amount of time to run compared to other
more rapid methods such as SAXS (Kijawara and Miyamoto 2007). A number of
NMR techniques exist, these include one-dimensional pulse NMR which can be
used for determining relaxation times and primary structures of carbohydrates and
sugars in solution, solid-state high-resolution NMR is applied to determine the
2  Processing and Characterization of Natural Polymers 43

structure of polymers in viscose solution, gel and solid forms while two-dimen-
sional and tree-dimensional NMR techniques provide information on the primary
and secondary structures and conformation of polymers (Kijawara and Miyamoto
2007). The technique chose therefore depends on the nature of the polymer to be
analyzed and the information required.
Analysis of polymers using the NMR technique is based on the chemi-
cal shifts and relaxation times recorded from an NMR spectrometer. Reading of
1HNMR signal peaks at specific regions of the spectrum between 2 and 6 ppm

provides information of the polymer being analyzed such that proper translation
of the presence of particular peaks at certain points of the NMR spectra provides
information on the presence of certain structures in the object being analyzed.
Table 2.4 summarizes 1H NMR chemical shifts for identifying monomer units of
polysaccharides.
The relaxation time relates to the local tumbling motion and conformational
changes of polymers under NMR. The time-dependent structure and dynamics of a
polymer such as hydration structure, helix–coil transition, amorphous and crystal-
line structures, sol–gel transition, and the structure-dependent molecular motion

Table 2.4  Chemical shifts (ppm) of monosaccharides from acetone at 2.225 ppm in D2 at

22.27 °C (Kijawara and Miyamoto 2007)
Monosaccharidea Protons
H1 H2 H3 H4 H5 H6 H7 CH3 NAc

Β-d-Glc-(1→
α-d-Glc-(1→ 5.1 3.56 3.72 3.42 3.77 3.77 3.87 – –
4.4 3.31 3.51 3.41 3.45 3.74 3.92 – –
α-d-Man-(1 1.9 3.98 3.83 3.70 3.70 3.78 3.89 – –
β-d-Man-(1 4.7 4.04 3.63 3.58 3.37 3.76 3.93 – –
α-d-Gal-(1→ 5.2 3.84 3.90 4.02 4.34 3.69 3.71 – –
β-d-Gal-(1→ 4.5 3.52 3.67 3.92 3.71 3.78 3.75 – –
β-d-GlcNAc-(1→ 4.7 3.75 3.56 3.48 3.45 3.90 3.67 – 2.04
α-d-GalNAc-(1→ 5.2 4.24 3.92 4.00 4.07 3.79 3.68 – 2.04
β-d-GalNAc-(1→ 4.7 3.96 3.87 3.92 3.65 3.80 3.75 1.23 2.01
α-l-Fuc-(1→ 5.1 3.69 3.90 3.79 4.1–4.9b – – 1.28 –
α-l-Rha-(1→ 4.9 4.06 3.80 3.46 3.74 – – – –
4.5 3.27 3.43 3.61 c – – 1.32 –
β-d-Xyl-(1→
3-θ-Me-α-l-Fuc-(1→ 4.8 3.70 3.40 – 3.89 – – 1.32 –
3-θ-Me-α-l-Rha-(1→ 5.0 4.24 3.59 3.52 3.77 – – 1.32 –
2,3-di-θ-Me-α-l-Rha-(1→ 5.1 3.94 3.52 3.41 3.73 – – – –
3,6-di-θ-Me-β-d-Glc-(1→ 4.7 3.34 3.31 3.51 3.51 3.66 3.78 –
aThese are average values for nonreducing terminal sugars linked by a glycosidic linkage to the
adjacent monosaccharides. Signals for protons at the ring carbons are shifted downfield when
linked by another monosaccharide at the hydroxyl group of that carbon
bThese are signals which are considerably vary more than other signals due to conformational

features
cH5ax 3.29; H5eq 3.93
44 O. Olatunji and O. Richard

can be obtained from the relaxation times. This involves the spin–lattice relaxation
time (T1) and the spin–spin relaxation time (T2).
T1 can be measured using repeated pulse sequence of π–τ–2/π radio frequency
through the inversion recovery method using the following equation:
ln(A∞ − Aτ ) = ln 2A∞ − τ/T1 (2.5)
Aτ and A∞ represent the magnitude of the recovering vector of magnetization
evolved the pulse at time t =  ∞ and t = τ . A plot of ln(A∞ − Aτ )) against τ . T1
also relates to viscosity η and temperature T (Bovey 1972).

128π 3 µ4 a3  η 
  
1
= (2.6)
T1 h2 r6 kT

where µ denotes a nuclear moment, a is the effective radius of a spherical mol-

T1 decreases in proportion to ŋ/T and a3 increases with r6. The effective volume
ecule, and r is the distance from the observed nucleus to its magnetic neighbor.

a3 is replaced with the molar volume in the case of oligosaccharides and polysac-
charides in solution. T1 as a function of the correlation time indicated the degree of
molecular motion, and T1 takes a minimum at the temperature when the relaxation
occurs according to the dipole–dipole interaction,
The correlation time is given by:
τc = 4π 3 a3 η/3kT (2.7)
The spin–spin relaxation time T2 is used in extreme situations of low viscosity
and fast motion. T2 is derived using the Carr-Purcell method or the Meiboom Gill
(CPMG) method (Carr and Purcell 1954; Meiboom and Gill 1958). In the case of
spin–spin relaxation time pulse sequence (π/2)−τ −πγ −2τ −πγ −2τ −πγ −ρ . . .
at τ pulse intervals.

2.4.3 X-ray Diffraction

The extent of crystallinity, crystalline microstructure, occurrence of amorphous

structure and the phases present in a polymeric material can be determined using
X-ray diffraction. The working principles of X-ray diffraction are based on the dif-
fraction and interference of X-ray beams as they leave a crystal. XRD can also
provide other information about a material such as the orientation of the filler
within the polymer or the orientation of the polymer itself. Example, biaxially
orientated polypropylene properties vary significantly from that of polypropylene
with other orientations.
The crystallization of a polymer sample can also be measured in situ while the
process is ongoing. This can allow for controlling parameters during processing.
Sample for XRD must be well crystallized and well oriented in order to achieve
good quality readings. There are a variety of methods for preparing samples for
2  Processing and Characterization of Natural Polymers 45

XRD analysis, for example, starch powders and films can be pretreated bzxy dry-
ing and conditioning in a desiccator prior to XRD analysis (Detduangchan et al.
2014).
For a diffraction to occur Bragg’s law must be obeyed
n = 2d sin θ (2.8)
where n = 1, 2, 3,…, d is the spacing between adjacent plane, λ is the wavelength
of the X-ray, and the diffraction angle is 2θ kl.
Here we look at some XRD processing methods that have been used for natural
polymers (Polnaya et al. 2013). The starch sample was dried into powdered form
and tightly packed in a sample holder of the X-ray diffractometer. X-ray beam at
30 kV and 30 mA was passed through the sample scanning at a diffraction angle
of 2θ  = 5° to 5° at 0.40 intervals with a rotary speed of 30 min−1 and a count
time of 1 s. The degree of crystallinity was obtained by identifying an amorphous
region and a crystalline region by plotting a smooth curve on the diffractogram.
This is illustrated in Fig. 2.14.
Crystallinity is calculated using the following equation:
Crystallinity (%) − Ac /(Ac + Am ) × 100 (2.9)
where Ac and Am are the area of the crystalline and amorphous regions
respectively.
Figure 2.15 shows the X-ray diffraction curves, which is a plot of X-ray inten-
sity against diffraction angle, for native sago starch (NSS) (a) and sago starch

Fig. 2.14  Smooth curve on diffractogram showing amorphous and crystalline portions of a

starch sample. Reproduced from Polnaya et al. (2013) under IFRJ open access stated terms
46 O. Olatunji and O. Richard

Fig. 2.15  Intensities for
native sago starch (a) and
sago starch treated by
phosphorylation with 5 %
sodium tripolyphosphate
STPP (b) and cross-linking
with 4 % phosphorous
oxychloride (POCl3) (cN)
(Polnaya et al. 2013).
Reproduced from Polnaya
et al. (2013) under IFRJ open
access stated terms

treated by phosphorylation with 5 % sodium tripolyphosphate STPP (b) and cross-
linking with 4 % phosphorous oxychloride (POCl3) (c).
The plot shows that native starch shows a C-type crystalline pattern which is
suggested by the weak diffraction pattern at a diffraction angle of 5.67° and broad
peaks at 15.3°, 17.12°, 18.08°, and 23.46°. These crystalline patterns are typical
of native sago starch as it has been observed in other studies on native sago starch
where similar peaks were exhibited (Leong et al. 2007). The nature of crystallinity
shown by the material, in this case starch is indicative of the composition. In this
case starch with relatively high amylose content is reported to display such XRD
peaks (Polnaya et al. 2013; Ahmad et al. 1999). Further study of the X-ray dif-
fraction graphs shows that the phosphorylation and the cross-linking had no effect
on the crystallinity of the starch. Although the peaks at 18° disappeared and new
peaks were formed at 17.88° and 17.84° for cross-linked and phosphorylated sago
starch, the degree of crystallinity was not much affected.

2.4.4 Thermogravimetry

Thermal characterization of polymers to determine the behavior of the polymer

under different temperature conditions is usually carried out using DSC or TGA.
Thermogravimetry analysis involves monitoring the changes in the mass of a sub-
stance with respect to temperature over a given time under controlled atmospheric
conditions. The setup typically consists of a sensitive weighing balance, a pan
connected to the weighing balance, and a high temperature furnace with an inlet
and purge for inert gas (which could be helium, nitrogen, or argon). The change in
2  Processing and Characterization of Natural Polymers 47

mass over the duration of heating is indicative of the degradation property of the
material at different temperatures.

2.4.5 Differential Scanning Calorimetry

The differential scanning calorimeter typically consists of two heating pans con-
nected to heating plates and a temperature reader connected to a computer. This is
illustrated in Fig. 2.16. The process involves placing the polymer sample on one of
the heating pans while the other pan acts as a reference pan. Heat is then applied
at a constant heat flow rate. The temperature readings of both pans are recorded at
different times and heat flow.
Here we look at examples where the thermal properties of nanocellulose-coated
sisal fiber-reinforced PLLA is obtained using DSC (Lee et al. 2012a, b). 20 mg of the
nanocomposite sample is placed on the heating pan. This particular process involves
a heating period where the sample was heated at a rate of 10 °C min−1, followed
by a cooling period where the sample is cooled at a rate of 50 °C min−1, and then
another heating period where the sample is reheated at a rate of 10 °C min−1 to a
temperature of 210 °C. The heating curves are then plotted for each heating and cool-
ing cycle. The crystallinity of the composite after thermal processing is calculated
from the Eq. 2.10. The properties obtained for each sample are shown in Table 2.5.
�Hm − �Hc
xc = × 100 % (2.10)
(1 − f )�Hm0

Fig. 2.16  DSC thermograms of electrospun polystyrene microfibers showing neat polystyrene

PS (100:0:0) and polystyrene loaded with 6 and 9 % cellulose whiskers (CNW) using an equiva-
lent amount of nonionic surfactant (S). Reproduced with permission from Rojas et al. (2009).
License number 3632200995714. Original Publisher John Wiley and Sons
48 O. Olatunji and O. Richard

Table 2.5  Crystallization Sample Heating Tg (°C) Tc (°C) Tm (°C) Xc (%)

and melt behavior of neat
PLLA 1st 63 113 171 18 ± 2
PLLA and its fiber/BC
2nd 61 110 169
reinforced hierarchical
composites Tg, Tc, Tm PLLA–sisal 1st 57 100 168 21 ± 3
and xc are glass transition 2nd 59 103 168
temperature, crystallization, PLLA–DCNS 1st 57 88 168 20 ± 3
temperature, melt 2nd 62 93 169
temperature and crystallinity PLLA–HNSF 1st 57 94 166 18 ± 2
of the composites based 2nd 57 94 166
on the 1st heating curve, PLLA–sisal–BC 1st 55 83 165 23 ± 4
respectively (Lee et al. 2nd – – 168
2012b) PLLA–DCNS–BC 1st 56 85 163 18 ± 3
2nd – – 166
PLLA–HNSF–BC 1st 54 81 165 24 ± 4
2nd – – 167

where xc is the crystallinity of the composite Hm, Hc, f, and H0m are the melting
enthalpy and cold crystallization enthalpy determined from DSC curves, weight
fraction of the reinforcing phase (20 wt%) and the melting enthalpy of pure crys-
talline PLLA (75.57 Jg−1) respectively.
The transition temperature can also be obtained from dynamic mechanical anal-
ysis, this is discussed in the next subsection. Differential scanning calorimetry for
thermal characterization of natural polymer-based materials include electrospun
polystyrene cellulose nanofibers (Rojas et al. 2009). In this case the glass trans-
mission temperature for electrospun polystyrene with varying amount of cellulose
nanowhiskers were compared (Fig. 2.16). The said fibers were electrospun at 20 %
PS in THF, Q ¼ 0.2 mL/min, 40 kV, distance ¼ 16 cm. Electrospun microfibers of
cellulose nanowhiskers showed lower glass transition temperature of 78 °C com-
pared to film casted polystyrene films with the same amount of cellulose nano-
whiskers which had a glass transition temperature of 93 °C (Rojas et al. 2009).
This is attributed to high voltage used in the electrospinning process causing some
structural modifications in the polystyrene nanocellulose fiber. The difference in
glass transition temperature of electrospun fibers compared to film casted fibers
with the same contents indicated that the processing method has an effect on the
structural properties of the material.

2.4.6 Mechanical Characterization

Tensile Strength Test

The tensile test is most commonly applied to polymer materials to establish the
amount of work input required to cause the material to yield or fail. Properties
such as stress at break, elongation at break, Young’s modulus, and work of failure
can be obtained from a static strength test on a polymer material. The standard
2  Processing and Characterization of Natural Polymers 49

procedure for natural polymer materials is the same for other synthetic materials.
This generally involves placing a strip of known dimension, i.e., width thickness
and length, between two grips of a tensile testing machine. At a set speed the strip
is pulled apart as the force applied varies with the displacement/elongation of the
polymer strip (Singh et al. 2009).
A typical tensile testing machine consists of a station and a static crosshead,
grips, load sensor, and a monitor or computer which records and displays the force
displacement profile for the test.
The tensile properties can be calculated from the following equations (Belton
et al. 1989):
Lmax
t= (2.11)
Ai

�lb
ε= × 100 (2.12)
li

YM = dL/dm/Ai (2.13)

δ
w = AUC × (2.14)
Ai
where Lmax is the maximum load, Ai is the initial cross-sectional area of the sam-
ple, li is the initial gauge length, Δlb is the increase in the length at the break-
ing point, dL/dm is the slope of the linear portion of the elastic deformation, w is
a function of the work done in the breaking of a film specimen and representa-
tive of film toughness. AUC refers to the area under the curve (Singh et al. 2009).
The results obtained are dependent on humidity and temperature, therefore these
parameters should be noted and kept constant as much as possible.
The tensile properties of biopolymers derived from fish (Olatunji et al. 2014;
Santos et al. 2014), jute/natural rubber composite (Pantamanatsopa et al. 2014)
have been reported. Table 2.6 lists Young’s modulus, elongation at break and stress
at peak for some natural polymer-based materials.
Dynamic Mechanical Analysis (DMA)
Dynamic mechanical analysis refers to the study of a material’s behavior under
sinusoidal applied force applied at a frequency f Hz and an angular frequency of
ω. A phase lag δ usually exists between the stress and strain of a viscoelastic body.
Such that the dynamic stress σ and strain ε can be expressed as:
ε = εo sin(ωt) (2.13)

σ = σo sin(ωt + δ) (2.14)
50 O. Olatunji and O. Richard

Table 2.6  Mechanical properties of some natural polymer materials

Material Elongation (%) Stress at break Young modulus Reference
(N/mm2) (N/mm2)
Fish scale 393.45 1.8105 0.2324 Olatunji et al.
biopolymer (2014)
Gelatin + glycerol 71.66 1.040 1.452 Jadhav et al.
(2010)
Wheat 0.94 15.2175 154.27 Komuraiah et al.
starch + cotton (2013)
Rice starch + cotton 1.28 12.828 119.57 Komuraiah et al.
(2013)
Fish gelatin + nano- 18 17 650 Santos et al.
cellulose (2014)

The stress can be divided into real and imaginary parts. The real part refers to the
ability of the material to store energy and release this energy when deformed while
the imaginary part represents the energy lost as heat during deformation. Including
the in-phase and out-of-phase components the stress can be expressed as:
σ = σo sin(ωt) cos δ + σo cos(ωt) sin δ (2.15)
where (σo cos δ) is the in-phase component and (σo sin δ) is the out-of-phase com-
ponent. These define the real and imaginary moduli E′ and E′′ respectively as
follows:
σ = εo E ′ sin(ωt) + εo E ′′ cos(ωt) (2.16)

σo
E′ = cos δ (2.17)
εo

σo
E ′′ = sin δ (2.18)
εo

ε = εo exp(iωt) (2.19)

σ = σo exp(ωt + δ)i (2.20)

σ σo σo
E∗ = = eiδ = (cos δ + i sin δ) = E ′ + iE ′′ (2.21)
ε εo εo
Such a relationship between the shear modulus G* and storage modulus G′ and
the loss modulus G′′ can be expressed as:
G∗ = G′ + iG′′ (2.22)
Or in terms of phase angle as:
G′′
tan δ = (2.23)
G′
2  Processing and Characterization of Natural Polymers 51

Fig. 2.17  Modulus of elasticity for natural neat natural rubber (NR), unmodified jute fiber in
natural rubber matrix (UN) and treated jute fiber with natural polymer matrix (Pantamanatsopa
et al. 2014)

While the storage modulus relates to the stiffness of the material or Young’s modu-
lus, the loss modulus relates to the internal friction of the material. Factors such as
motions at the molecular level, transitions, relaxation, and morphology affect the
loss modulus.
The glass transition temperature is also obtainable from dynamic mechanical
analysis. The glass transition temperature of −60 °C was obtained for natural rub-
ber matrix using the DMA (Pantamanatsopa et al. 2014). As shown in Fig. 2.17,
the sharp drop in the modulus beyond 60 °C corresponds to a glass transition state
of the material. Where NR100 indicates a neat natural rubber polymer, UN10 indi-
cates a natural rubber polymer matrix with untreated jute fiber reinforcement and
T10 indicates natural rubber matrix containing treated jute fiber as reinforcement.

2.4.7 Microscopy

Most commonly used microscopy method for characterization of natural polymers

is scanning electron microscope (SEM) and transmission electron microscope
(TEM). Scanning electron microscopy is often used to obtain microphotographs
of fibers and composites in the micro- and nanoscale in order to study the mor-
phology of the material. In an example the morphology of electrospun cellulose
nanowhiskers were obtained using a Hitachi S-3200N variable pressure SEM
(Fig.  2.13). The process required collecting of the electrospun nanowhiskers on
aluminum foils, shadowing with an approximately 150 Å thick layer of gold–pal-
ladium. The prepared sample was observed at a working distance of 3 and 60 mm
and accelerating voltage of between 0.3 and 30 kV. Scanning electron microscopy
gives good information about the dispersion of the fiber within the composite and
compatibility between the polymers. It has been widely applied in studying natural
52 O. Olatunji and O. Richard

Fig. 2.18  TEM images of fish scale gelatin with cellulose nanocrystals as reinforcement

(Olatunji and Olsson 2015)

polymers used as fillers, fibers, or matrix in films and composite. Figure 2.18

shows scanning electron micrographs of fish scale gelatin with cellulose nanocrys-
tals from wood (Olatunji and Olsson 2015).
Through the micrographs issues such as aggregation or beading can be
observed. For example, Rojas et al. (2009) observed using SEM that the bead-
ing in electrospun polystyrene–cellulose nanowhiskers was significantly reduced
with the use of nonionic surfactant by comparing micrographs of the electrospun
fibers with and without surfactant. The diameters of the fibers formed were also
observed using SEM.
TEM is often used for more detailed analysis of polymer morphology.
Figure 2.19 shows the TEM images of electrospun polystyrene–cellulose nanow-
hiskers. For this purpose a Hitachi HF-2000 TEM using a cold field emission elec-
tron source at a 200 kV voltage was employed. TEM grids which are made up of
3-mm copper mesh were placed on the collector plate during electrospinnig to col-
lect the electrospun samples on the TEM grids. Figure 2.18a shows TEM of neat
electrospun polystyrene films without cellulose nanowhiskers, these had smoother
surface while those of electrospun polystyrene with cellulose nanowhiskers shown
in Fig. 2.18b were rougher and darker. Figure 2.18c shows the cellulose containing
fibers at a higher magnification to show the surface roughness.

2.4.8 Fourier Transform Infrared (FTIR) Spectrometry

FTIR is commonly used to analyze polymers with the aim of identifying the
chemical bonds which exist within a sample. FTIR could also be a measure of
2  Processing and Characterization of Natural Polymers 53

Fig. 2.19  TEM of electrospun microfibers from neat polystyrene (a) and from polystyrene filled
with 9 % cellulose nanowhiskers in the presence of equivalent amount of nonionic surfactant
(b, c). Operating conditions: 20 % PS in THF. Q = 0.2 mL/min, 40 kV, distance = 16 cm. Repro-
duced with permission from Rojas et al. (2009). License number 3632200995714. Original Pub-
lisher John Wiley and Sons

compatibility between polymers. Figure 2.20 shows FTIR of lignin, cellulose, and

hemicellulose obtained from biomass.
The main functional groups represented by the peaks in Fig. 2.20 for the three
components, lignin, cellulose, and hemicellulose are shown in Table 2.7. Using
FTIR the observation of the peaks translate to the presence of specific bonds
which can be used to determine the chemical components of a sample. In the par-
ticular study by Yan et al. (2007), the FTIR was used to identify the components of
biomass from plants prior to pyrolysis. The pyrolysis of biomass is of importance
in the industries for energy generation from biomass from waste plant product as
an alternative to fossil fuel which is fast depleting (Yan et al. 2007).
54 O. Olatunji and O. Richard

Fig. 2.20  FTIR of lignin, cellulose, and hemicellulose (image obtained from Yan et al. 2007
with permission from Elsevier, license number 3633510294045)

Table 2.7  The main functional groups in lignin, cellulose, and hemicellulose from FTIR
Wave number (cm−1)a Functional groups Compounds
3600–3000 (s) OH stretching Acid, methanol
2860–2970 (m) C–Hn stretching Alkyl, aliphatic,
aromatic
1700–1730 (m), 1510–1560 (m) C=O stretching Ketone and carbonyl
1632 (m) C=C Benzene stretching ring
1613 (w), 1450 (w) C=C stretching Aromatic skeletal mode
1470–1430 (s) O–CH3 Methoxyl–O–CH3
1440–1400 (s) OH bending Acid
1402 (m) CH bending
1232 (s) C–O–C stretching Aryl–alkyl ether linkage
1215 (s) C–O stretching Phenol
1170 (s), 1082 (s) C–O–C stretching vibration Pyranose ring skeletal
1108 (m) OH association C–OH
1060 (m) C–O stretching and C–O C–OH (ethanol)
deformation
700–900 (m) C–H Aromatic hydrogen
700–400 (w) C–C stretching
as strong, m middle, w weak
2  Processing and Characterization of Natural Polymers 55

Fig. 2.21  FTIR of fish gelatin with and without cellulose nanowhiskers (obtained from Santos
et al. 2014 with permission from Elsevier, License number 3633491129379)

In another example Santos et al. (2014) obtained the FTIR analysis of gelatin
with and without nanocellulose blended (Fig. 2.21). This was carried out using
a Varian 660-IR spectrophotometer equipped with an attenuated total reflec-
tance (ATR) sampling accessory scanning at a wavelength between 4000 and
6500 cm−1. The samples showed similar peaks for both samples with a slight
increase in intensity at 3280 cm−1, representative of the amide A functional
group, for the nanocellulose-blended sample (Gelatine + 10 %NC). There is also
a decreased intensity at the amide I, II, and III group seen at 1361, 1542, and
1238 cm−1 wavelength respectively. These are attributed to the protein dilution
effect and/or the cellulose gelatin interactions (Santos et al. 2014).
More recent approach to FTIR makes use of nondestructive methods in which
the samples require no pretreatment. As a further example the FTIR analysis of
nanocellulose is carried out and shown in Fig. 2.22. To obtain FTIR peaks for the

Fig. 2.22  FTIR of nanocellulose extracted from wood

56 O. Olatunji and O. Richard

nanocellulose gel, a diamond ATR spectrometer accessory attached to the Agilent

Cary 630 FTIR using a diamond crystal at a wavelength ranging between 63,000
and 350 cm−1 is employed. The sample of nanocellulose gel is placed on the sam-
ple window and the press closed to allow contact. The sample is then scanned to
obtain the absorbance plot (Fig. 2.22). The main peaks obtained occur at about
3600 cm−1 which is indicative of the presence of OH group due to intramolecular
hydrogen bonding. The other major peak occurs at about 1600, which is indicative
of absorbed water. Similar peaks for nanocellulose have been reported by (Zain
et al. 2014) using a Perkin Elmer type FTIR.

2.5 Conclusion

Processing of natural polymers into blends and composites consisting of natural

polymers as fillers or as matrices in combination with other polymers can sig-
nificantly alter the properties and applicability of the polymer. Further processing
techniques common to industry such as extrusion, electrospinning, and micronee-
dle production can be used to form products from natural polymers for different
applications. Natural polymers can be characterized using methods such as XRD,
TEM, DMA, and TGA. Although a variety of other methods exist and others are
yet to emerge the techniques discussed here are those with known applications in
natural polymers. In each case, examples of reported applications of these pro-
cessing and characterization techniques to natural polymers are provided. Some
characterization techniques presently applicable to synthetic polymers are not
applicable to natural polymers due to limitations in their physical or mechanical
properties. Modifications of these properties have extended some of the methods
previously limited to only synthetic materials to natural polymers.
Acknowledgment  This research was supported by the international Foundation for Science,
Stockholm Sweden through a grant to Ololade Olatunji.

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Zain NFM, Yusop SM, Ahmad I (2014) Preparation and characterization of cellulose
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Zema L et al (2012) Injection moulding and it’s application to drug delivery. J Control Release
159(3):324–331
Chapter 3
Extraction, Purification, and Modification
of Natural Polymers

Abdalbasit Adam Mariod

3.1 Introduction

“Polymer” signifies “numerous parts” (from the Greek poly, signifying “numerous,”
and meros, signifying “parts”). Polymers are large molecules with molar masses
extending from thousands to millions. About 80 % of the organic chemical i­ndustry
is committed to the generation of manufactured polymers, for example, plastics,
material filaments, and engineered rubbers. A polymer is incorporated by syntheti-
cally joining together numerous small molecules into one big molecule. The small
molecules used to synthesize polymers are called monomers. Manufactured poly-
mers can be called expansion polymers, structured from monomer units specifically
joined together, or build up polymers, framed from monomer units joining such
that a small molecule, ordinarily water, is delivered amid every response. Polymers
are broadly found in nature. The human body, plants, and animals contain numer-
ous natural polymers, for example, proteins, cellulose, gelatine, starch, chitin, and
chitosan (Joesten and Wood 1996). These polymers can be extracted, purified, and
modified for improved functionality in various applications.

A.A. Mariod (*) 
College of Sciences and Arts, University of Jeddah, P.O. Box 110, 21931 Alkamil,
Saudi Arabia
e-mail: basitmariod@yahoo.com

© Springer International Publishing Switzerland 2016 63

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_3
64 A.A. Mariod

3.2 Extraction, Purification, and Modification of Gelatin

Gelatin or gelatin (from Latin: gelatos meaning “stiff,” “frozen”) is a translucent,

dismal, weak (when dry), flavorless polymer, obtained from collagen acquired
from different animal by-products. It is generally utilized as a gelling agent in
food, pharmaceuticals, photography, and cosmetic manufacturing. Substances con-
taining gelatin or working in a comparative manner are called gelatinous. Gelatin
is an irreversibly hydrolyzed type of collagen. Gelatin is a mixture of peptides and
proteins delivered by incomplete hydrolysis of collagen separated from the skin,
bones, and connective tissues of animals, for example, cattles, chicken, pigs, and
fish. Gelatin is derived from collagen by partial thermal hydrolysis. It is an impor-
tant functional biopolymer that has a very broad application for food, material,
pharmacy, and photography industries (Hao et al. 2009).
Despite the fact that gelatins from beef and pork have been broadly consid-
ered, less work has been published on extraction techniques and utilitarian prop-
erties of gelatin from cold-blooded animals, for example, fish (Cho et al. 2005;
Gudmundsson 2002a, b), recently insect was used as a new gelatine source
(Mariod et al. 2011a). Since it is acquired by the corruption of a bigger struc-
ture, it brings about a wide-mixed variety of peptide chain species. This degra-
dative methodology is totally arbitrary, therefore most gelatin arrangements are
not homogenous resulting in variation in molecular weight or weight distribu-
tion (Gomez-Guillen et al. 2002). Due to the acid obligation of cross-connecting
in fish skin collagen, gentle treatment with acid ought to be sufficient to influ-
ence solubilisation (Norland 1990). Such treatment prompts a sort A gelatin with
an isoelectric point between pH 6 and 9, which conveys a net positive charge in
most food uses (Stainsby 1987). Various studies on collagen from diverse spe-
cies have concentrated on acid extractions (Montero and Gomez-Guillen 2000).
On the other hand, for the assembling of food grade gelatin from fish, citric acid
is widely utilized as it does not impart objectionable color or odor to the gelatin
(Gudmundsson and Hafsteinsson 1997). The sort of acid used, the ionic strength,
and the pH emphatically impact swelling properties and solubilization of collagen.
Expanding hydrogen ions supports the entrance of water to the collagen filaments,
and this water is held in by electrostatic powers between charged polar gatherings
(electrostatic swelling) or by hydrogen holding between uncharged polar groups
and negative atoms (lyotropic hydration) (Gómez-Guillén and Montero 2001).

3.2.1 Primary Structure of Gelatin

The essential structure and composition of gelatin resembles the parent colla-
gen. This likeness has been substantiated for a few tissues and animal varieties
(Fernandez-Diaz et al. 2001). Slight contrasts are because of the wellspring of
crude material in mix with the pretreatment and extraction methodology utilized.
The functional group of gelatin, for example, –NH2, –SH, and –COOH endow
3  Extraction, Purification, and Modification of Natural Polymers 65

Fig. 3.1  A typical structure of gelatin polypeptide (Source Liu et al. 2011)

it as lessening and stabilizing agent to diminish Au(III) to structure a gold col-

loid. As shown in Fig. 3.1, decently scattered gelatin stabilized gold nanoparticles.
Gelatin polypeptide chains with predominately loop compliance are unreservedly
soluble in water at raised temperature (>35 °C). Nonetheless, gelatin particles con-
nected together to structure aggregates when gelatin solution and gelatin-AuNPs
colloid were gradually cooled to room temperature.

3.2.2 Secondary Structure of Gelatin

Different aspects of gelatin behavior in solution and gels have been disclosed in
connection to its molecular weight. Gelatin is not polydispersed totally, yet has a
distinct molecular weight dissemination design, which relates to the α-chain and
its oligomers (Buice et al. 1995). One to eight oligomers may be discovered or dis-
tinguished in solution, however the likelihood of higher numbers being available
cannot be precluded. Oligomers of three α-chains will exist primarily as in triple
helices while a certain extent will exist as augmented α-polymers bonded arbitrar-
ily by end-to-end or side-to-side bonds. The vicinity of oligomers with expand-
ing quantities of α-chains becomes more complex and hard to peruse (Buice et al.
1995). Polyacrylamide gel electrophoresis (PAGE) is utilized to acquire pro-
foundly precise molecular weight spectra of both commercial and laboratory gela-
tins, giving quantitative separation (Buice et al. 1995).

3.2.3 Denaturation of Collagen to Obtain Gelatin

The least complex approach to change collagen to gelatin is to denature soluble col-
lagen. It includes hydrolysis catalyzed by enzyme, acid, or soluble base. Thermal
denaturation happens in gentle conditions by warming the collagen in neutral or
somewhat acidic conditions to around 40 °C (Gimenez et al. 2005). At the point
66 A.A. Mariod

Fig. 3.2  Denaturation of collagen to obtain gelatin (Reproduced from Samal et al. (2012), with
permission from Royal Society of Chemistry, License number 3634181495264)

when collagen is warmed for amplified periods of time, the triple helix atomic
structure unfolds at a certain temperature, and the collagen breaks down into irregu-
lar peptide chains in arrangement. Collagen that is denaturated by heat and gets dis-
solved in water is alluded to as gelatin (Fig. 3.2). The move is sharp and complete
within a couple of minutes over a little temperature interim. The activation energy
for denaturation is pretty nearly 81 kcal (Jusila 2004). By then just the hydrogen
bonds and hydrophobic bonds that assistance to settle the collagen helix are broken,
creating the filaments and fibrils of collagen to separate into tropocollagen units.
The following venture, in the hydrolysis of collagen comprises in breaking the
intramolecular bonds between the three chains of the helix (Nishimoto et al. 2005).

3.2.4 Extraction of Gelatin

Two systems are typically used to produce gelatine from mammalians: the acid
and the basic methods. The gelatin arranged by the acid methodology is called
type A gelatin, while that arranged by the alkaline procedure is called type B gela-
tin (Schrieber and Gareis 2007). In spite of the fact that the property of collagen
in fish skin is not the same as that of well-evolved mammals and avian species,
the fish gelatin extraction techniques may in any case be isolated into two classes:
an acid methodology and an alkali procedure. Amid fish gelatin extraction, the
3  Extraction, Purification, and Modification of Natural Polymers 67

acid procedure alludes to the extraction that is done in an acid medium (Gómez-
Guillén and Montero 2001), and at times acid pretreatment before extraction is
applied. The alkaline procedure alludes to a pretreatment of fish skin with alka-
line solution, as a rule taken after by balance with an acid arrangement, hence
the extraction may be done in an alkaline, neutral, or acid medium (Montero and
Gómez-Guillén 2000; Jamilah and Harvinder 2002; Zhou and Regenstein 2004).
The acid methodologies are primarily utilized with pig skin and fish skin and
sometimes bone crude materials. It is essentially one in which the collagen is acid-
ified to about pH 4 and later heated stepwise from 50 °C to boiling to denature and
to solubilize the collagen. From that point the denatured collagen or gelatin solu-
tion must be defatted, separated to high clarity, thought by vacuum evaporation or
film ultrafiltration treatment, to a sensibly high fixation for gelation and afterward
drying by passing dry air over the gel. The last process is one of the crushing and
mixing to consumer prerequisites and packaging. The subsequent gelatin has an
isoionic purpose of 7–9 in light of the seriousness and term of the acid handling of
the collagen which causes constrained hydrolysis of the asparagine and glutamine
amino acid side chains (Cole 2000).
The alkali method is utilized in bovine hide and collagen sources where the
animals are generally old at slaughter. The procedure is one in which collagen is
submitted to a caustic soda or extensive liming methodology preceding extrac-
tion. The alkali hydrolyses the asparagine and glutamine side chains to glutamic
and aspartic acids rapidly, with the outcome that the gelatin has a customary
isoionic point of 4.8–5.2, then again, with shortened (7 days or less) alkali treat-
ment, isoionic points as high as 6 are delivered. After the alkali processing, the
collagen is washed free of alkali and treated with acid to the desired extraction pH
(which has a stamped impact on the gel quality to the thickness degree of the last
item). The collagen is then denatured and changed over to gelatin by heating, as
with the acid method. In view of the alkali treatment, it is regularly important to
demineralise the gelatin solution to remove excessive amounts of salts utilizing ion
exchange or ultrafiltration. From there on the procedure is the same for all the acid
extraction methods—vacuum vanishing, filtration, gelation, drying, crushing, and
mixing (Cole and Roberts 1996).

3.2.5 Extraction of Fish Gelatin

Gelatin can be acquired from the skin and bones of animals as well as from fish.
The waste from fish handling in the wake of fileting can represent as much as
75 % of the total catch weight (Shahidi et al. 1995). Around 30 % of such waste
comprises of skin and bones with high collagen content that can be utilized to
produce fish gelatin (Gomez-Guillen et al. 2002). Extraction of gelatins from fish
skins and edible insects (sorghum and melon bugs) may provide an option to meet
requirements for Halal items and serve as an option for business sectors worried
about bovine spongiform encephalopathy (BSE). The yield and nature of gelatin
68 A.A. Mariod

are impacted not just by the species or tissue from which it is separated, but addi-
tionally by the extraction process, which may rely on pH, temperature, and time
during both pretreatment and extraction (Montero and Gómez-Guillén 2000;
Mariod et al. 2011a). Hence, an optimization of the extraction method ought to
enhance the extraction of fish gelatin. It is conceivable to acquire a light colored,
dry collagen separate from megrim skins by solubilizing collagen with consist-
ent moderate mixing overnight and uprooting the leftover, not solubilised, dim
skin. The dried collagen transforms into a soluble gelatin when dissolved in warm
water. Swelling limit of collagen, pH of extraction, and ionic strength, which shifts
relying upon the kind of acid utilized, are important for the utilitarian viability of
the extraction. Acetic acid and propionic acid delivered the most elevated swelling
limit and pH of extraction, prompting the most noteworthy viscoelastic and gelling
properties, particularly, when skins were pretreated with diluted NaOH and the pH
was adjusted to 4.5–5 (Gómez-Guillén and Montero 2001).

3.2.6 Insects Gelatin

Some insect species can be utilized to concentrate gelatine for sustenance pur-
poses, e.g., Aspongubus viduatus and Agonoscelis pubescens; the powdered adults
of these bugs demonstrated 27.0–28.2 % crude protein, respectively. The two bugs’
proteins contained 16 known amino acids, including the majority of the essential
amino acids. Compared with the amino acid profile prescribed by FAO/WHO,
the bug protein was of mid-range quality because of its medium substance of fun-
damental amino acids (Mariod et al. 2011a). Gelatin was extracted from melon
bug and sorghum bug utilizing boiling hot water, gentle acid, and distilled water
extraction techniques.
The extraction of gelatin from melon bug utilizing hot water extraction gave
high return of 150 mg/g representing 3.0 % after gentle acid extraction and dis-
tilled water extraction at 125–33.0 mg/g representing 2.5–0.6 %, respectively.
While the extraction of gelatin from sorghum bug demonstrate similarly as hot
water extraction was high trailed by gentle acid and distilled water extraction with
the yield of 152, 66, and 134 mg/g. Amid insect gelatin extraction, basic and acid
pretreatments demonstrated impacts on removing noncollagenous proteins with
least collagen loss, and alkaline pretreatment followed by hot point water extrac-
tion demonstrated a superior impact than acid pretreatment,which was far superior
to soluble pretreatment followed by distilled water extraction.
SDS-PAGE pattern demonstrated low molecular weight chains, and the two
insect’s gelatin contained protein with molecular weight of 40 kDa as a funda-
mental part. The differential scanning calorimetry thermograms results affirm
no difference between extraction methods concerning the separated gelatin qual-
ity. FTIR spectra of melon and sorghum bug gelatins were comparative and the
absorption bands were situated in more than 6 bands in melon bug gelatin and just
6 bands in sorghum bug gelatine (Fig. 3.3). Amide II bands of gelatins from both
3  Extraction, Purification, and Modification of Natural Polymers 69

Fig. 3.3  FTIR spectra (3282–3263, 2927–2921, 1400–1395, 1068–1042 cm−1) of melon bug

(MB 1, 2, 3) and sorghum bug (SB 1, 2, 3) gelatin extracted using three methods (Source Mariod
et al. 2011b)

Fig. 3.4  Scanning Electron Microscopy (SEM) micrographs for gelatine from melon bug
(a) and sorghum bug (b)

melon and sorghum bugs showed up at around 1554 cm−1, while Amide I bands
(1734–1632 cm−1) seemed just in melon bug.
Microstructures of the insect gelatin examined with the scanning electron
microscope (Fig. 3.4) showed that melon bug exhibited the finest gelatin network
with very small voids. Melon bug gelatin showed finer structure with smaller pro-
tein strands and voids than sorghum bug gelatin (Mariod et al. 2011b).
70 A.A. Mariod

3.3 Extraction, Purification, and Modification of Chitin

After cellulose, chitin is the most far reaching biopolymer in nature. Chitin and
its subsidiaries have awesome monetary worth on account of their biological
activities and their industrial and biomedical applications. It can be obtained from
three sources, to be specific shellfish, insects, and microorganisms. However,
the principle commercial sources of chitin are shells of shrimps, crabs, lobsters,
and krill that are supplied in huge amounts by the shellfish handling commercial
enterprises. Extraction of chitin includes two stages, demineralization and depro-
teinisation, which can be directed by two techniques, chemical or biological. The
chemical method obliges the utilization of acids and bases, while the biological
method includes microorganisms. Although lactic acid bacteria are mostly applied,
other microbial species, including proteolytic bacteria have additionally been
effectively executed, and blended cultures including lactic acid-producing bacteria
and proteolytic microorganisms (Arbia et al. 2013).
The structure of chitin is indistinguishable to that of cellulose, with the excep-
tion of the substitution of the OH group on the C-2 carbon of each of the glu-
cose units with a –NHCOCH3 group. In industrial processing, chitin is removed
from crustaceans by acid treatment to break down calcium carbonate took after
by alkaline extraction to solubilize proteins. Furthermore, a decolorization step is
regularly added to evacuate extra pigments and acquire a colorless material. These
treatments must be adjusted to every chitin source, owing to contrasts in the ultras-
tructure of the introductory materials. The subsequent chitin needs to be evaluated
as far as purity and color since residual protein and pigment can result in issues for
further use, particularly for biomedical items. By fractional deacetylation under
alkaline conditions, one acquires chitosan, which is the most imperative chitin
derivative regarding applications (Rinaudo 2006).
Of late, chitin acquired by extraction from fungi mycelia is gaining signifi-
cance. Fungi mycelia can be developed during the time by fermentation under
submerged culture which is quick and synchronized and can be performed in bio-
reactors with all robotized and controlled conditions; along these lines, mycelial
biomass delivered in every batch is homogeneous, in quality and quantity (Zapata
et al. 2012).
Álvarez et al. (2014) isolated chitin from the Ganoderma lucidum submerged
cultures mycelium. In the said study, the extraction of chitin was carried out
through five separate measures which included basically three stages: pulveriza-
tion of the mushroom, deproteinization of the mycelia with NaOH solution, and
a process of decolorization with potassium permanganate and oxalic acid. The
five assays for the chitin isolation were made as follows: for the first three assays,
the dried fungi biomass was pulverized and was subjected to alkaline treatments
with sodium hydroxide solution (NaOH) at a ratio of 1:30 (w/v). For each assay,
molar concentrations, temperature, and reaction time were varied; for A1 assay:
1 M NaOH 1:30 (w/v), 40 °C for 2 h; for A2 assay: 1 and 2 M NaOH 1:30 (w/v),
90 °C for 2 h; and finally for A3 assay: 2 and 4 M NaOH 1:30 (w/v), 90 °C for 2 h.
3  Extraction, Purification, and Modification of Natural Polymers 71

In A3 assay, a decolorization process was added; the crude chitin was treated with
10  g L−1 potassium permanganate for 1 h and then reacted with 10 g L−1 oxalic
acid for 1 h. Assays A4 and A5 had different processes. In A4 assay, the dried
fungi biomass was pulverized and a part of it was subjected to extraction twice
with hot water for removing some unwanted polysaccharides. The residue was col-
lected and dried in an oven at 40 °C. Deproteinization was performed using alka-
line treatment with different molar concentrations of NaOH (2, 4, 6, and 8 M) in
1:20 (solid:alkali) ratio, at 100 °C for 3 h. The suspension was centrifuged and
washed with deionized water until reaching neutrality. Decolorization process was
similar to the one carried out in A3 assay.
In A5 assay, the dried fungi biomass was pounded and blended with deion-
ized water, and afterward the mixture was subjected to a sonication process for
40 min and afterward centrifuged. The powder was washed with ethanol for 24 h.
Deproteinization was performed utilizing alkaline treatment with 4 M NaOH at
the ratio of 1:20 (w/v), at 100 °C for 2 h. This treatment was repeated three times.
The suspension was centrifuged and washed with deionized water until reach-
ing neutrality. Decolorization procedure was similar to the one carried out in A3
assay. At the end of the processes of each assay, each suspension was centrifuged
and washed with deionized water until reaching neutrality and dried at 50 °C until
reaching a constant weight. Finally, the amount of chitin obtained by each method
was separated by drying weight method. Álvarez et al. (2014) reported that the
amount of chitin produced was between 78 and 413 mg g−1 in different assays
(milligrams of chitin for grams of dry biomass). A1 and A2 show the highest
amounts of chitin production. A difference between A1 and A2, with A3, A4, and
A5 was the decolorization treatment with potassium permanganate (KMnO4) and
oxalic acid (C2H2O4); A3, A4, and A5, showed a low chitin yield likely due to the
strong oxidant nature of potassium permanganate. It is possible that the treatment
has not only removed pigments but also chitin (Álvarez et al. 2014).
Alkali chitin was prepared by dissolving chitin at low temperature in NaOH
solution. The chitin is first dispersed in concentrated NaOH and allowed to stand
at 25 °C for 3 h or more; the alkali chitin obtained is dissolved in crushed ice
around 0 °C (Einbu et al. 2004). The resulting chitin is amorphous and, under
some conditions, it can be dissolved in water, while chitosan with a lower degree
of acetylation (DA) and ordinary chitin are insoluble. This phenomenon might be
related to the decrease of molecular weight under alkaline conditions and to some
deacetylation; and to get water solubility, the DA has to be around 50 % and, prob-
ably, that the acetyl groups must be regularly dispersed along the chain to prevent
packing of chains resulting from the disruption of the secondary structure in the
strong alkaline medium (Kubota and Eguchi 1997).
Recently, Arguelles-Monal et al. (2003) used interesting techniques for chi-
tin extraction, such as rheology, turbidimetry, and fluorescence; they found that
alkali chitin solubilized in cold (~0 °C) aqueous NaOH (16 % w/w) forms an
LCST solution with a critical temperature around 30 °C. A chitin gel, obtained
from the solution by washing to extract NaOH, was found to be temperature-
and pH-sensitive. A volume phase transition at ~21 °C was observed as the
72 A.A. Mariod

result of the influence of temperature on polymer–polymer and polymer–water

interactions such as hydrogen bonding and hydrophobic interactions. This tran-
sition is observed only within a narrow range of pH (7.3–7.6) and modifies the
mechanical shear modulus as a function of oscillating variation in temperature
(Rinaudo 2006).

3.4 Extraction, Purification, and Modification of Chitosan

Chitosan is a linear polysaccharide composed of randomly distributed β-(1-4)-

linked d-glucosamine (deacetylated unit) and N-acetyl-d-glucosamine (acetylated
unit). It is made by treating shrimp and other crustacean shells with the alkali
sodium hydroxide (Fig. 3.5).
Chitosan is an assumed nontoxic and hydrophilic polysaccharide acquired from
shellfish sources, for example, crabs and shrimps. Bioapplications of chitosan
were presumably more advanced in the most recent 25 years; chitosan is as of now
better known to be a dietary supplement to people in general than its other bio-
medical applications due to its ease, large-scale accessibility, antimicrobial activ-
ity, and in addition biodegradation and biocompatibility (Wenjuan et al. 2012).

3.4.1 Extraction and Isolation of Chitosan

Paul et al. (2014) separated and secluded chitosan from the prawn waste (shell).
In the first place, they removed the exoskeletons independently and washed thrice
with tap water and after that twice with distilled water. At that point they dried in
a hot air oven for around 24 h at 55 °C. The sample obtained was soaked in boil-
ing 4 % sodium hydroxide utilizing 1000 mL beaker for 60 min. The example was
evacuated and after that permitted to cool at room temperature for 30 min. They
were then crushed further into little pieces of around 0.5–5.0 mm. The specimen
acquired was demineralized utilizing 1 % hydrogen chloride with four times its
amount. They were then soaked for 24 h to remove minerals. The above examples
were treated with 50 ml of 2 % sodium hydroxide for 60 min. The remaining parts

Fig. 3.5  Chemical structure of chitosan (Wang and Uchiyama 2013)

3  Extraction, Purification, and Modification of Natural Polymers 73

of the specimen were washed with deionized water and after that drained off. The
deacetylation methodology was then done by adding half sodium hydroxide to the
obtained test on a hot plate and bubbling it for 2 h at 100 °C. The example was
then permitted to cool at room temperature for 30 min. At that point they were
washed consistently with half sodium hydroxide. The test acquired is filtered (chi-
tosan is obtained). The sample was left revealed, and oven dried for 6 h at 110 °C.
The acquired chitosan was cleaned to make it suitable for utilization. The puri-
fying procedure was outlined in three stages—evacuation of insoluble with filtra-
tion, precipitation of chitosan with 1 N sodium hydroxide, and demetallization of
recovered chitosan (Paul et al. 2014).
Paul et al. (2014) reported that the molecular weight of their prepared chitosan
was variable due to high temperature, alkali concentration, time of reaction, chitin
concentration, dissolved oxygen deliberation, shear stress, etc., and the determined
molecular weight is 159,653 g/mol. They checked the solubility of the obtained
chitosan with five different solvents that is water, ethanol, NaOH, acetic acid, and
lactic acid. They found that their chitosan was not soluble in alkaline or neutral
solution, but was soluble in acidic condition, whereas compared with lactic acid;
it was more soluble in acetic 90–95 % solubility. The pH value of chitosan also
varies from the range 6.2–8.0. Paul et al. (2014) study shows that the production of
chitosan from sea prawn waste (shell) would successfully reduce the environmen-
tal pollution.
A common method for the synthesis of chitosan is the deacetylation of chitin
using sodium hydroxide in excess as a reagent and water as a solvent. This reac-
tion pathway, when allowed to go to completion (complete deacetylation) yields
up to 98 % product. The degree of deacetylation (%DD) can be determined by
NMR spectroscopy, and the %DD in commercial chitosan ranges from 60 to
100 %. On average, the molecular weight of commercially produced chitosan
is between 3800 and 20,000 Da. The amino group in chitosan has a pKa value
of ~6.5, which leads to a protonation in acidic to neutral solution with a charge
density dependent on pH and the %DA value. This makes chitosan water solu-
ble and a bioadhesive which readily binds to negatively charged surfaces such as
mucosal membranes (Shahidi and Jozef 1991; Thomas et al. 2005).
When the degree of deacetylation of chitin reaches about 50 %, it becomes
soluble in aqueous acidic media and is called chitosan. The solubilization occurs
by protonation of the –NH2 function on the C-2 position of the d-glucosamine
repeat unit, whereby the polysaccharide is converted to a polyelectrolyte in acidic
media. Chitosan is the only pseudonatural cationic polymer and thus, it finds many
applications that follow from its unique character (flocculants for protein recovery,
depollution, etc.). Being soluble in aqueous solutions, it is largely used in differ-
ent applications as solutions, gels, or films and fibers. The first step in character-
izing chitosan is to purify the sample: it is dissolved in excess acid and filtered on
porous membranes (with different pore diameters down to 0.45 mm). Adjusting
the pH of the solution to ca. 7.5 by adding NaOH or NH4OH causes flocculation
due to deprotonation and the insolubility of the polymer at neutral pH. The poly-
mer is then washed with water and dried.
74 A.A. Mariod

Recently, Chenite et al. (2001) obtained a water-soluble form of chitosan at

neutral pH in the presence of glycerol 2-phosphate. They obtained stable solutions
at pH 7–7.1 and room temperature, but a gel formed on heating to about 40 °C.
They noticed that the sol–gel transition was partially reversible and the gelation
temperature depended slightly upon experimental conditions.
Puvvada et al. (2012) synthesized chitosan through various chemical steps, they
prepared the chitin from the crude shells exoskeleton of shrimp that initiate chi-
tosan synthesis with the removal of the proteins in the shells followed by demin-
eralization for the removal of the carbon and other salts present in the crude form
which will be preceded by the deacetylation of the chitin that would result in chi-
tosan. They obtained regular chitosan but a polymer of pharmaceutical grade has
to fall in the region of its predetermined quality aspects and usually commercial
chitins are prepared by a first step of deproteinisation followed by a second step of
demineralization.
Chatterjee et al. (2005) used the cell wall of fungi as an alternative source of
chitosan, they manipulated the fungal culture media and fermentation condition
and they provided a chitosan of more consistent physicochemical properties com-
pared to that derived chemically from chitin. They isolated chitosan from Mucor
rouxii cultured in three different media, viz., molasses salt medium (MSM), potato
dextrose broth (PDB), and yeast extract peptone glucose (YPG) medium under
submerged condition and their yield has been found to be almost the same. These
authors found production of chitosan to be influenced by the composition of the
growth medium, as the highest amount was obtained with MSM. Chitosan from
MSM was less polydispersed and more crystalline compared to those from YPG
and PDB.
Chitosan is not soluble in water, which limits its wide application, particularly
in the medicine and food industry. Water-soluble chitosan (WSC) can be prepared
by hydrolyzing chitosan using hydrogen peroxide H2O2 under the catalysis of
phosphotungstic acid in homogeneous phase under optimum conditions of H2O2
2 % (v/v), phosphotungstic acid 0.1 % (w/v), 65 °C, and 40 min, affording the
maximum DE. The average degree of polymerization (DP) of chitooligosaccha-
rides was approximately 7. The WSC content in the product and the WSC yield
were 94.7 and 92.3 % (w/w), respectively. All products were white powders and
soluble in water (Xia et al. 2013).
Song et al. (2013) extracted the chitosan from the blowfly larvae by a series
of steps: deproteinization with sodium hydroxide, decolorization with sodium
hypochlorite, decalcification with oxalic acid, and deacetylation with concen-
trated sodium hydroxide solution. These authors reported that the recovery rate of
chitosan from the blowfly was 26.2 %, the molecular weight of the blowfly chi-
tosan (501 kDa) was lower than that of the commercial chitosan (989 kDa), and
its degree of deacetylation (DDA) (87.9–89.6 %) was also higher than that of the
commercial chitosan (83.8–85.8 %).
Wu et al. (2011) obtained Chitosan oligomers (COS) by enzymatic hydrolysis
and H2O2 oxidative treatment, and then they separated it into different fractions
using ultrafiltration membranes. Each COSM fraction prepared using enzymatic
3  Extraction, Purification, and Modification of Natural Polymers 75

hydrolysis retained its structure, especially the reduced end residue (–NH2 group),
and had a peak for molecular weight. On the other hand, each COSH fraction pre-
pared by oxidative treatment had partly damaged –NH2 groups and two peaks for
molecular weight. These results indicate that the same COS fractions prepared
by the two methods differ in their amino groups and in their molecular weights,
though they can both pass through the same size ultrafiltration membrane. The dif-
ferences in molecular weights due to ultrafiltration separation can be observed for
all fractions.

3.5 Extraction, Purification, and Modification of Cellulose

3.5.1 Cellulose Extraction

Cellulose is a long polysaccharide chain that does not translocate within a tree or
exchange carbon with the atmosphere following its formation. Radiocarbon dates
performed on cellulose alone are therefore thought to be a good measure of past
atmospheric 14 °C. A study by Gaudinski et al. (2005) indicated that the Jayme-
Wise method produces extracts that are most chemically similar to pure cellulose
as compared to other cellulose extraction methods. A batch processing protocol
for Jayme-Wise cellulose extraction, developed by Leavitt and Danzer (1993) and
commonly used for stable isotope measurements, involves three steps to isolate
alpha-cellulose, each step followed by multiple water washes:
1. Cleaning: treatment in a Soxhlet system with toluene and ethanol to remove
waxes, fats, oils, resins, and other compounds soluble in organic solvents.
2. Isolation of holocellulose: bleaching with a mixture of sodium chlorite and ace-
tic acid to remove lignins.
3. Isolation of alpha-cellulose: treatment with strong base followed by a neutral-
izing acetic acid wash.
Cellulose consists of β-glucopyranosyl residues joined by 1 → 4 linkages.
Cellulose crystallizes as monoclinic, rodlike crystals. The chains are oriented par-
allel to the fiber direction and form the long b-axis of the unit cell (Fig. 3.6). The
chains are probably somewhat pleated to allow intrachain hydrogen bridge forma-
tion between O-4 and O-6, and between O-3 and O-5. Intermolecular hydrogen
bridges (stabilizing the parallel chains) are present in the direction of the a-axis
while hydrophobic interactions exist in the c-axis direction. The crystalline sec-
tions comprise an average of 60 % of native cellulose. These sections are inter-
rupted by amorphous gel regions, which can become crystalline when moisture is
removed. The acid- or alkali-labile bonds also apparently occur in these regions.
Microcrystalline cellulose is formed when these bonds are hydrolyzed. This par-
tially depolymerized cellulose product with a molecular weight of 30–50 kD, is
still water insoluble, but does not have a fibrose structure (Belitz et al. 2009).
76 A.A. Mariod

Fig. 3.6  Unit cell of cellulose (Source Belitz et al. 2009)

3.5.2 Extraction of Alpha-Cellulose

A protocol (Fig. 3.7) is described to isolate small quantities of highly purified cel-

lulose for isotopic analysis of 10–100 mg samples of secondary (Pinus sylvestris
L.) and primary (Rubus idaeus L.) plant cell wall material. Elemental analysis
of 350 cellulose samples isolated from pine wood samples estimated the relative
carbon content to be ca. 43.7–1.2 %. This value indicates that the cellulose qual-
ity is high and that the protocol is highly reproducible. High-performance anion
exchange chromatography with pulsed amperometric detection of hydrolysis prod-
ucts quantified the purity of the cellulose as ca. 99 % of wood cellulose and pri-
mary cell wall cellulose. DRIFT spectroscopy corroborated this purity and found
no evidence of cellulose degradation. Carbon isotopic composition of the puri-
fied cellulose using mass spectrometry was measured with an accuracy of 0.11 %
(standard deviation). The method is rapid (56 samples may be routinely processed
within 8 h) and requires only standard laboratory equipment and chemicals.
Samples (10–100 mg, routinely 50 mg) were weighed into 10 mL Pyrex2
tubes and the combined weight was measured on a balance capable of recording
to 10 μg. Subsequently, 2.0 mL of acetic acid (80 %; v/v) and 0.2 mL of con-
centrated nitric acid (69 %; v/v) were added. In order to minimize losses, it was
essential that the tube walls remained free of sample material at all stages of the
protocol. Any sample left adhering to the inner wall of the test tube was washed
3  Extraction, Purification, and Modification of Natural Polymers 77

Fig. 3.7  The protocol for

purification of cellulose
from micro samples of plant
cell wall material using
acetic acid:nitric acid for
simultaneous delignification
and removal of noncellulose
polysaccharides. Obtained
with permission from
Brendel et al. (2000) License
number 3622470298990

downward to aid complete extraction: this was achieved by adding liquid extrac-
tion reagent in two parts, the first to suspend the sample and the second to rinse
the tube wall. Samples were then suspended by careful vortexing.
The tubes were sealed using screw caps fitted with Teflon liners and placed
into a heating block preheated to 120 °C for 20 min (extraction). Once cooled,
2.5 mL of ethanol (99 %; v/v; AnalaR1 quality) was added and the samples were
78 A.A. Mariod

centrifuged (5 min at 2000 rpm). The supernatant was then carefully decanted

and the pellets were washed sequentially as follows: (1) with 2–2.5 mL ethanol,
to remove extraction breakdown products; (2) with 2–2.5 mL deionized water, to
remove traces of nitric acid (omission of this water wash resulted in samples with
increased nitrogen content); (3) with 2–2.5 mL ethanol; and (4) with 2–2.5 mL
acetone (general purpose grade). Steps (3) and (4) allowed more thorough wash-
ing and sample dehydration. Between each wash, samples were pelleted by cen-
trifugation and the supernatant was discarded. In order to free the sample tubes for
further extractions, it was necessary to transfer the purified cellulose into 1.5 mL
microfuge tubes using 0.4 mL of acetone. Subsequently, the inner walls of the
sample tubes were rinsed with a further 0.6 mL of acetone and the washings were
transferred to the microfuge tubes. The 1 mL sample was then centrifuged for
10 min in a vacuum evaporator and the remaining acetone was decanted. Samples
were recentrifuged in the vacuum evaporator until no further weight loss could be
recorded. Samples were kept in sealed bags containing anhydrous silica gel. For
quantitative analysis the samples can be dried to constant weight in the Pyrex test
tubes.

3.5.3 Modification of Cellulose

Cellulose macro- and nanofibers have gained increasing attention due to the high
strength and stiffness, biodegradability and renewability, and their production and
application in development of composites. Application of cellulose nanofibers for
the development of composites is a relatively new research area. Cellulose macro-
and nanofibers can be used as reinforcement in composite materials because of
enhanced mechanical, thermal, and biodegradation properties of composites.
Cellulose fibers are hydrophilic in nature, so it becomes necessary to increase their
surface roughness for the development of composites with enhanced properties. In
the present article, we have reviewed the surface modification of cellulose fibers
by various methods. Processing methods, properties, and various applications of
nanocellulose and cellulosic composites are also discussed in this article.

3.6 Extraction, Purification, and Modification of Starch

3.6.1 Starch Methods of Extraction

Starch is widely distributed in various plant organs as a storage carbohydrate. As

an ingredient of many foods, it is also the most important carbohydrate source in
human nutrition. In addition, starch and its derivatives are important industrially,
for example, in the paper and textile industries. Starch is isolated mainly from the
sources. Starch obtained from corn, potatoes, cassava, and wheat in the native and
3  Extraction, Purification, and Modification of Natural Polymers 79

modified form accounted for 99 % of the world production. Some other starches
are also available commercially. Recently, starches obtained from legumes (peas,
lentils) have become more interesting because they have properties which appear
to make them a suitable substitute for chemically modified starches in a series
of products. Starches of various origins have individual, characteristic properties
which go back to the shape, size, size distribution, composition, and crystallin-
ity of the granules. The existing connections are not yet completely understood
(Belitz et al. 2009).
Starch production is an isolation of starch from plant sources. It takes place in
starch plants. Starch industry is a part of food processing which is using starch as
a starting material for production of starch derivatives, hydrolysates, dextrins. At
first, the raw material for the preparation of the starch was wheat. Currently, main
starch sources are:
• maize (in America)—70 %,
• potatoes (in Europe)—12 %,
• wheat—8 %,
• tapioca—9 %,
• rice, sorghum, and others—1 %.

3.6.2 Corn Starch Production

Alkaline cooking, which is referred to as nixtamalization, is an important pro-

cess used in the preparation of tortillas, com chips, taco shells, tamales, and other
Mexican-style foods. During nixtamalization, com is first cooked in the presence
of lime, steeped, and then washed to produce nixtamal. Nixtamal is stone-ground
to form a soft, moist dough that is called masa (Gomez et al. 1987; Serna-Saldivar
et al. 1990). Although nixtamalization is widely used in the food industry, a com-
prehensive, fundamental understanding of starch functionality and its thermal
behavior in masa is still lacking.
The starch gelatinization process during masa preparation has not been stud-
ied in detail, and only few reports are available on the effect of masa components
on starch functionality (Bryant and Hamaker 1997; Campus-BaypoJi et al. 1999).
Starch in masa has been characterized without extracting starch in purified form
(Gomez et al. 1991, 1992), although studies of them are helpful in identifying
changes in starch granules during masa.

3.6.3 Starch Extraction from Masa

Starch from masa was extracted using two different methods. For Method 1,
freeze-dried masa was ground into flour using a cyclone sample mill. Masa (10 g)
was dispersed in 500 mL of distilled water by stirring using a magnetic stirrer for
80 A.A. Mariod

6 h. The mixture was passed through a loose cotton wool plug in a funnel and then
it was filtered using a 60 µm polyester mesh screen under suction to remove coarse
particles. The filtrate containing starch was collected and washed with distilled
water containing 1 % (w/v) sodium hydroxide four times and then washed with
distilled water several times. The recovered starch was dispersed in 500 mL of
distilled water and filtered using 10-µm nylon mesh under suction to remove fine
contaminants. Starch was recovered and freeze-dried at −55 °C and 200 mTorr
pressure for 36 h. Samples were stored in sealed polypropylene containers until
used.
For Method 2, dried masa was ground into flour using a cyclone sample mill.
Starch in masa was extracted by the protease. Dry masa flour (5 g) was mixed with
330 units of thermolysin in the presence of 5 mM calcium chloride in 100 mL
of aqueous solution in a screw cap Erlemmeyer flask. The mixture was kept in a
60 °C water bath for 4 h and gently hand-mixed at 30-min intervals. The enzyme
action was terminated by adding 0.03 g of EDTA to the reaction mixture. After
cooling to room temperature, the mixture was filtered through a loose cotton
wool plug in a funnel to remove coarse particles and washed five times with dis-
tilled water to remove residual proteins. Starch was recovered by centrifuging the
suspension at 1300×g for 7 min after each washing step. Recovered starch was
­redispersed in 500 mL of distilled water and filtered using a 60-µm polyester mesh
screen under suction to remove coarse particles. The filtrate containing starch was
collected and washed with distilled water containing 1 % (w/v) sodium hydroxide
four times and then washed with distilled water several times. Recovered starch
was dispersed in 500 mL of distilled water and filtered using a 10-µm nylon mesh
screen under suction to remove fine contaminants and freeze-dried using a freeze
dryer at −50 °C and 100 m Torr vacuum pressure for 36 h. Samples were stored in
sealed polypropylene containers until used.
Han et al. (2005) reported that thermolysin (the proteolytic enzyme) can be suc-
cessfully used to remove proteins associated with starch granules. Accordingly,
thermolysin digestion was used to remove starch granules from protein matri-
ces in masa. Starch isolated by enzyme digestion gave starch with significantly
(P < 0.05) less protein compared with starches isolated by water washing.
According to these results, 57.7 % of protein in masa can be removed by water
washing method, and the rest of the starch granule bound proteins (35.6 %) are
removed by thermolysin action method. A very small amount (6.5 %) of total pro-
tein in masa is left with purified starch granules after thermolysin treatment. In
SEM images (Figs. 3.7 and 3.8), protein and endosperm remnants were clearly
visible among starch granules isolated by washing water method, whereas digest-
ing protein with thermolysin method resulted in relatively “uncontaminated”
starch granules. The starch yield of thermolysin extraction (weight of granules
extracted from masa) was 60.0 % (w/w, SD 2 %). The starch extraction effi-
ciency of the method was 74 % (w/w, db) based on the amount of starch in masa
(Ratnayake et al. 2007).
3  Extraction, Purification, and Modification of Natural Polymers 81

Fig. 3.8  Scanning electron
microscopic images of masa
(a), starch isolated by Method
1 (b), and starch isolated by
Method 2 (c). Magnification
2500×. Source Ratnayake
et al. (2007)
82 A.A. Mariod

3.6.4 Potato Starch Production

The production of potato starch comprises the steps such as delivery and unload-
ing potatoes, cleaning, rasping of tubers, potato juice separation, starch extraction,
starch milk rafination, dewatering of refined starch milk, and starch drying.

3.6.5 Starch Extraction

After separation of potato juice the pulp is directed to the washing starch sta-
tion, to isolate the starch. The most used are stream-oriented washers. In these
machines pulp diluted with water is washed with a strong stream of water to flush
out the milk starch. The mash smuggling with water is a waste product—dewa-
tered potato pulp. Starch milk is contaminated by small fiber particles (potato tis-
sue fragments) and the remaining components of the potato juice—that is why it is
called raw starch milk.

3.6.6 Starch Milk Raffination

Raw starch, milk is purified in the refining process. This involves the removal of
small fibers from the starch milk and then the removal of juice water and starch
milk condensation. For this purpose, the screens and hydrocyclones are commonly
used. Hydrocyclones due to the low output (approximately 0.3 m3/h) are con-
nected in parallel and works as multihydrocyclones. For the starch milk desanding
bihydrocyclones are used. In order to prevent enzymatic darkening of potato juice
the chemical refining of starch is carried out using sulfurous acid. Refined starch
milk has a density of about 22° Be, which is about 38 % of starch.

3.6.7 Dewatering of Refined Starch Milk and Starch Drying

It is a suspension of starch in water, which needs dewatering up to 20 % of mois-

ture. This is equivalent to the moisture content of a commercial starch when
stored. High temperature cannot be used in this process because of the danger
of starch gelatinization which destroys granular structure. It may result in sig-
nificant changes of the functional starch properties. Therefore, removal of excess
water from milk shall be done only under conditions that prevent the gelatinization
of starch.
Dewatering of refined starch milk is carried out in two stages. In the first stage,
the excess water is removed by means of a rotary vacuum filter. Second, moist
3  Extraction, Purification, and Modification of Natural Polymers 83

starch is dried, without starch pasting. For this purpose a pneumatic drier is used.
In this device moist starch (with water content 36–40 %) is floating in strong and
hot (160 °C) air flow and then dried during 2–3 s. Then, the starch is separated
from hot air in cyclones. Due to the short time of high temperature drying and
intensive water evaporation from the starch granules, its surface is heated only to
40 °C (Pałasiński 2005).

3.6.8 Rice Starch Extraction

Rice starch is used as an additive in various food and industrial products. With
the inherent merits of small and uniform size distribution of rice starch and its
white color and clean odor, deserts and bakery products are some of the favora-
ble applications among processed foods. Rice protein in the endosperm, however,
tightly associates on the surface of starch granules and the difficulty in removing
the protein makes the starch isolation more costly compared to other starches. To
isolate rice starch, alkaline solvents, surfactants, or protein hydrolyzing enzymes
could be used to remove rice protein from rice flour (Maningat and Juliano 1979).
Alkaline solvents such as NaOH and surfactants such as dodecylbenzene sulfonate
(DoBS) and sodium lauryl sulfate (SLS) are commonly used in the protein extrac-
tion for starch isolation. These solvents destruct the oligomeric protein structures
and transform them to the soluble forms. An aqueous 1.2 % DoBS solution con-
taining 0.12 % sodium sulfite was more effective than 0.2 % NaOH or 1.2 % SLS
containing 0.12 % sodium sulfite for the protein removal to isolate rice starch. The
protein removal efficiency could be further increased by repeating short extraction
steps (1–2 h) with fresh solution. Raising the extraction temperature was not rec-
ommendable because the protein extractability increase was minor, but starch loss
became significant. Pasting characteristics of rice starch were highly dependent on
the residual protein content, and protein removal imparts to the paste a viscosity
increase and a pasting temperature decrease (Lim et al. 1999).

3.6.9 Modification of Starches

Starch properties and those of amylose and amylopectin can be improved or

“tailored” by physical and chemical methods to fit or adjust the properties to a
particular application or food product. When starch granules are damaged by
grinding or by application of pressure at various water contents, the amorphous
portion is increased, resulting in improved dispersibility and swellability in cold
water, a decrease in the gelatinization temperature by 5–10 °C, and an increase
in enzymatic vulnerability. In bread dough made from flour containing damaged
starch, for instance, the uptake of water is faster and higher and amylase degrada-
tion is greater. Extruded starches are easily dispersible, better soluble, and have
84 A.A. Mariod

a lower viscosity. The partial degradation of appropriately heated amylase shows

that chemical changes also occur at temperatures of 185–200 °C. Apart from malt-
ose, isomaltose, gentiobiose, sophorose, and 1,6-anhydroglucopyranose appeared
(Belitz et al. 2009).

3.7 Extraction, Purification, and Modification of Pectin

Pectin is a polysaccharide consisting mostly of two moieties. These are homoga-

lacturonan, (1-4) linked, a-d-galacturonic acid and its methyl ester; and rham-
nogalacturonan I, (1-2) repeating linked, a-l-rhamnose-(1-4) a-d-galacturonic
acid disaccharide. Rhamnogalacturonan II contains arabinan, galactan, and arabi-
nogalactan side chains. These monosaccharide units comprise most of sugar units
found in pectin. Natural polymer like pectin is easy to isolate and purify, it is non-
toxic and biocompatible (Khule et al. 2012).
Pectin is widely distributed in plants. It is produced commercially from the
peels of citrus fruits and from apple pomace (crushed and pressed residue). It
is 20–40 % of the dry matter content in citrus fruit peel and 10–20 % in apple
pomace. Extraction is achieved at pH 1.5–3 at 60–100 °C. The process is care-
fully controlled to avoid hydrolysis of glycosidic and ester linkages. The extract
is concentrated to a liquid pectin product or is dried by spray or drum drying into
a powdered product. Purified preparations are obtained by precipitation of pectin
with ions which form insoluble pectin salts (e.g., Al3+ , followed by washing with
acidified alcohol to remove the added ions, or by alcoholic precipitation using iso-
propanol and ethanol (Belitz et al. 2009).

3.7.1 Extraction and Isolation of Pectin

Extraction of pectin most commonly occurs using a dilute mineral acid, usually
hydrochloric, sulfuric, or nitric acids. Commercial pectin extraction is as the fol-
lows. A factory receives previously washed and dried apple pomace or citrus peel
from a number of sources. The material is added to hot water and a dilute mineral
acid is added for extraction. Sufficient time elapses to allow the extraction to occur
and then the solids are separated from the pectin containing liquid through filtra-
tion or centrifugation. The remaining solution is concentrated and mixed with an
alcohol for pectin precipitation. The precipitated pectin is separated and washed
with alcohol to remove impurities. The pectin is dried, ground to a powder, and
blended with other additives, if necessary (IPPA 2001).
Many authors extracted and isolated pectin from different plant materi-
als, Khule et al. (2012) extracted and isolated pectin from dried citrus fruit peel
powder, where they blended 50 g of the powder with 300 ml distilled water. The
water to be used for extraction was acidified using 40 % citric acid and pH was
3  Extraction, Purification, and Modification of Natural Polymers 85

maintained at 1.2–2. The acidified mixture of blended peel powder was then
heated at 60 °C for around 120 min. After the heating period was over, the mixture
was passed through the twofold muslin cloth and was cooled to room tempera-
ture. They isolated the pectin using ethyl alcohol as precipitating agent. Following
that, concentrated pectin extracts were precipitated in 95 % ethanol. One volume
of extracts was added in various volumes of ethanol. The orange fruit extracts
and ethanol ratios (ER) were 1:0.5, 1:1, 1:1.5 and continuous stirring was done
in 15 min. Then the mixture was kept aside for 2 h without stirring. Pectin was
filtered through four-layered muslin cloth. The precipitate was washed 2–3 times
by ethyl alcohol, to further remove any remaining impurity. Finally, the precipitate
was kept for drying at 35–40 °C in hot air oven and percentage yield was found to
be around 18.21 %. It was then stored in desiccators until further use. Pectin was
extracted by water-based extraction technique and 9.1 g of pectin was obtained
from 50 g of dried citrus fruit peel. The highest pectin yield was obtained at
pH 2, the yield was peaked at the ER of 1:1. The yield ranged from 5.29 to 18.21 %
(Khule et al. 2012). The effects of temperature, time, and pH on pectin yield for
orange pectin using nitric acid extraction were investigated by Aravantinos-Zafiris
and Oreopoulou (1991). Optimal extraction conditions of pH 1.6, 84 °C, and
64 min resulted in yields up to nearly 26 % of the dried peel weight. Galacturonic
acid content, methoxyl content, and ash were reported to be independent of the
extraction variables. Optimal extraction conditions found through varying extrac-
tion time, pH, and temperature for pectin extraction from sugar beet pulp were
reported as the use of hydrochloric acid to adjust pH to 1.5 extracted for 4 h at
80 °C (Phatak et al. 1988). The resulting pectin yield was 19.53 % dry basis at
these extraction conditions.
Campbell (2006) successfully extracted pectin from watermelon rind using acid
and enzyme as comparative extraction methods. Pectin yields for the two extrac-
tion methods were increased through the optimization of extraction parameters.
Extraction using nitric acid and precipitation using isopropanol appeared to be
the best acid/alcohol combination. Further experimentation indicated that there
was not a difference in pectin yield due to solid-to-liquid ratio. No significant dif-
ference in pectin yield occurred with increasing temperature, although the trend
showed higher yields with increased temperature. An extraction temperature of
95 °C was chosen for further extractions. The use of Trichoderma viride cellu-
lase for watermelon rind pectin extraction resulted in a minimal amount of pec-
tin. Enzyme loading did not result in a significant difference in pectin yield for
Cellupract (Campbell 2006).

3.8 Extraction, Purification, and Modification of Lignin

Lignin is a natural, highly branched and amorphous, polymer of high molar mass,
acting as the essential glue that gives plants their structural integrity, and repre-
senting the second most abundant natural polymer on earth. As an integral part of
86 A.A. Mariod

Fig. 3.9  Three fundamental monolignols (and their respective phenylpropanoids): p-coumaryl

alcohol (p-hydroxyphenyl), coniferyl alcohol (guaiacyl), and sinapyl alcohol (syringyl) (Repro-
duced with permission from Pinkert et al. (2011) License number 3622560015292)

the secondary cell wall of plants, and due to its hydrophobic character, it plays an
important role in transporting water in plant stems. Lignin lacks a clearly defined
secondary or tertiary order and its variable composition depends on the plant
source. In a simplified way, lignin can be regarded as the polymerized product of
three fundamental phenylpropane units, commonly known as monolignols: p-cou-
maryl alcohol, coniferyl alcohol, and sinapyl alcohol. In the ligninmacromolecule,
these monolignols are incorporated in the form of phenylpropanoids: p-hydroxy-
phenyl (H), guaiacyl (G), and syringyl (S) (Figs. 3.7 and 3.8) (Pinkert et al. 2011).

3.8.1 Lignin Extraction with Ionic Liquids

To date, it is still impossible to study naturally occurring lignin in its unaltered

form, because all known isolation procedures result in chemical modification of its
three-dimensional network (Kilpelainen et al. 2007). After the first report in 2002
that some ILs can dissolve cellulose, wood scientists were gradually becoming
aware of the immense potential of ILs for their research. In 2007, Kilpelainen et al.
(2007) reported the complete dissolution of wood in ILs. The possibility to dissolve
lignin in ILs triggered investigations on both the nature and the chemical behav-
ior of IL-derived lignin (Zoia et al. 2011) and also includes studies on the depoly-
merisation of the IL-dissolved biopolymer. Pu et al. (2007) investigated a range of
imidazolium ILs for their ability to dissolve kraft lignin. In their study, up to 0.2
mass fraction of lignin could be dissolved in ILs containing triflate or methylsulfate
anions, and it was suggested that the IL anion dominates the dissolution behavior.
Imidazolium chlorides and bromides were less potent to dissolve kraft lignin, com-
pared to sulfur containing anions, and both tetrafluoroborates and hexafluorophos-
phates did not dissolve the polymer (Pu et al. 2007). However, the chemical nature
of kraft lignin—containing sulfur residues from the pulping process—cannot be
compared with that of native wood lignin, and caution is required when interpreting
3  Extraction, Purification, and Modification of Natural Polymers 87

these observations. Most ILs with cellulose-dissolving ability do also dissolve lignin
to a certain degree. This behavior is exploited to reduce the recalcitrance of ligno-
cellulosic biomass toward enzymatic hydrolysis. Especially, the IL 1-ethyl-3-meth-
ylimidazolium acetate ([EMIM]Ac) has been used to reduce both the lignin content
and the crystallinity of biomass prior to its hydrolysis (Kilpelainen et al. 2007).
Imidazolium acesulfamate ILs have the ability to dissolve wood lignin with-
out dissolving cellulose. In particular, 1-ethyl-3-methylimidazolium acesulfamate
exhibits physical properties that are desirable in industrial processing. The
extracted lignins possess both a larger average molar mass and a more uniform
molar mass distribution compared to lignin obtained from the kraft process, which
is the dominant process for the extraction of lignin in the pulp and paper indus-
try. These results represent a significant progress toward the development of supe-
rior methods for the environmentally benign extraction of wood lignin that still
allows exploiting the desirable mechanical properties of crystalline cellulose for
the production of advanced biocomposites. Viewed from a different perspective, it
allows to transform native wood into a lignin-deficient material with an increased
cellulose content, but without compromising its crystallinity. IL lignin removal has
numerous advantages compared to prevailing methods, representing an opportu-
nity for future biorefineries producing renewable feedstock material for aromatic
biochemicals and cellulosic biocomposites with the potential to transform cur-
rent industries such as the pulp and paper industry. In conclusion, IL extraction
of wood lignin holds promising potential for being a low-cost and environmental
benign method to obtain both uniform lignins and cellulosic-rich wood residues
with a high degree of crystallinity, which can be used for the manufacturing of
biocomposites with superior mechanical properties. However, it is equally impor-
tant to acknowledge the current limits and drawbacks of the studied IL lignin
extractions. Although the incorporation of the IL anion into the extracted lignin
was only observed at elevated extraction temperatures or with increased extraction
times, this does not imply a nonreactive IL anion in general. Both the wood load
and the wood particle size, used in the experiments, are far below the requirements
of the wood industry, and the results obtained cannot quite simply be compared to
those of large scale processes. Moreover, the wood samples were extensively dried
prior to use in the IL extraction experiments. Although it has been shown that
small amounts of residual water do not negatively impact the lignin extraction effi-
ciency, it is very likely that the water content of natural biomass material exceeds
this tolerance. In addition, both the high price and the environmental footprint of
imidazolium-based ILs require successful recycling for more than 100 times to
compare in the biomass arena (Pinkert et al. 2011).
Currently, the main industrial methods used for extracting lignin from woody
or nonwoody lignocellulosic feedstocks are the kraft, soda, sulfite, and organo-
solv processes (Pye and Lora 1991). Most of these methods require high tempera-
tures and high pressure. The high temperatures requested are usually reached by
conductive heating from an external heat source, which implies reaction times of
several hours. These long reaction times are not desirable because of high energy
consumption and multiple unwanted side reactions (Monteil-Rivera et al. 2012).
88 A.A. Mariod

Monteil-Rivera et al. (2012) used microwaves to isolate lignin from agricultural

residues, they used a central composite design (CCD) to optimize the processing
conditions for the microwave (MW)-assisted extraction of lignin from triticale
straw. They found that the maximal lignin yield (91 %) was found when using
92 % EtOH, 0.64 N H2SO4, and 148 °C. They compared the yield and chemical
structure of MW-extracted lignin to those of lignin extracted with conventional
heating. They reported that, under similar conditions, MW irradiation led to higher
lignin yields, lignins of lower sugar content, and lignins of smaller molecular
weights. Except for these differences the lignins resulting from both types of heat-
ing exhibited comparable chemical structures. Their present findings should pro-
vide a clean source of lignin for potential testing in manufacturing of biomaterials.

3.9 Conclusion

In recent years, there is a progressive shift in the field of natural polymers. The
improved interest is mainly due to the environmental concerns, which have sur-
faced recently and also due to the low cost involved in obtaining these polymers,
which is an ideal substitute for synthetic ones, which might be toxic. Natural poly-
mers from natural sources had its own advantages, such as no seasonal limit on
accessibility to raw materials, low inorganic salt content, and no regional limit on
industrial production. Some of these natural polymers are used as a possible food
ingredient or in the pharmaceutical industry. This review provided information on
the conditions suitable for the extraction, purification, and modification of natu-
ral polymers (gelatin, chitosan, pectin, starch, and lignin). Extraction techniques
showed rapid progress using most advancements easy to apply and give pure
bioactives.

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Chapter 4
Biomedical Application of Natural Polymers

Ololade Olatunji

4.1 Introduction

The main areas of biomedicine where biopolymers find applicability include

­tissue engineering, bone repair/replacement, dental repair/replacement, controlled
drug delivery and skin repair. The applicability of biopolymers in biomedical sci-
ence is largely due to their versatility which meets the wide variety of design and
functional requirements of the different tissue types. Biopolymers selected for
biomedical applications are selected based on the criteria which include material
chemistry, molecular weight, shape structure, hydrophobicity/hydrophilicity, lubri-
cating property, surface energy, degradation rate, water absorption, erosion mecha-
nism and solubility. Polymers are particularly attractive in biomedical application
as they possess these preferred criteria, particularly biocompatibility, porosity, can
undergo a diverse range of chemical and physical modification for specific tissue
regeneration requirement and they possess biological properties which are desir-
able for biomedical applications (Dhandayuthapani et al. 2011; Hutmacher 2001).
Biomedical application of natural polymers is often dominated by combination of
polymers with natural and synthetic bioactive particles towards attaining required
mechanical and biological performance (Roether et al. 2002).
Scaffold can be produced from combination of natural polymers with other natural
or synthetic polymers. Nanocomposite of silk fibroin, a natural protein from the silk
worm and sodium alginate also a natural polymer sourced from sea weed, were made
into fibrous scaffolds for tissue engineering (Zhang et al. 2015). Such composites can
be produced by methods such as electrospinning (Pu et al. 2015; Rajzer et al. 2014),

O. Olatunji (*) 
Chemical Engineering Department, University of Lagos, Akoka, Lagos, Nigeria
e-mail: Lolakinola@gmail.com

© Springer International Publishing Switzerland 2016 93

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_4
94 O. Olatunji

freeze drying (Lima et al. 2013), thermally induced phase separation (Zhang et al.
2015) and melt spinning (Cui et al. 2015) for use as various types of scaffolds.

4.2 Scaffolds for Tissue Engineering

The three main aspects of tissue engineering include seed cell proliferation–which
involves implanting of specialized cells into the organism, cell growth–which
involves introduction of growth factors which encourage tissue formation and the
third is scaffolding which involves inducing tissue formation or repair using the
supporting three-dimensional biomaterials known as scaffolds (Li et al. 2014a, b;
Dhandayuthapani et al. 2011; Langer et al. 1993) with the general goal of restora-
tion, maintenance or improvement of tissue functions.
A scaffold should be able to perform the following functions (Dhandayuthapani
et al. 2011):
(1) Promotion of interaction between the cell and biomaterial adhesion and
deposition
(2) Regulate transfer of essential substances such as nutrients, gases and regula-
tory factors necessary for cell growth, division and survival
(3) Controlled biodegradation rate synchronized with tissue regeneration rate
(4) Induce minimal inflammation and toxicity
Scaffolds serve as supportive structures for regeneration and restoring, and func-
tion to the tissue by acting as a temporary matrix for the cell to grow and multiply
into the desired tissue structure. Tissues such as skin, bones, ligaments, cartilage,
muscles, neural and vascular tissues can be regenerated using scaffolds. Scaffolds
are also used for controlled delivery of bioactive compounds such as drugs, pro-
teins and DNA. The advancement in tissue engineering in the past decade can be
attributed to advancement in the major research areas pertaining to tissue engi-
neering which includes material science, imaging, cell biology and cell material
interactions, and surface characterization, thus leading to more promising pros-
pects for treating a wider range of diseases and today there is a potential for regen-
erating every tissue in the body (Dhandayuthapani et al. 2011).
Scaffolds can be either biological, i.e. sourced from human or animal tissues;
they can also be synthetic, i.e. made from mainly synthetic polymers. Biopolymers
are widely used for scaffold production due to their biodegradability, biocompat-
ibility, microstructure, morphology, modifiable mechanical properties and ver-
satility. Research work into development of biologically active scaffold was first
presented in 1974 (Yannas et al. 1975) and later patented in 1977 (Yannas et al.
1977). There has since been gradual development in this area as this was followed
by studies to establish the principles for synthesizing a biologically active scaf-
fold, scaffold-induced tissue regeneration in skin, peripheral nerve and conjunctiva
(Yannas and Burke 1980; Yannas et al. 1981, 1982, 1985; Burke et al. 1981; Hsu
et al. 2000).
4  Biomedical Application of Natural Polymers 95

Biomaterials which are inert with modifiable structural and mechanical proper-
ties are proffered for use as scaffolds. Typically, porous scaffolds are made from
metals (e.g. steel and titanium), polymers (e.g. PLA and PGA), ceramics or com-
posites. Natural polymers commonly used in scaffold production include collagen,
fibrin, fibrinogen, platelet rich plasma, alginate, gelatin, albumin and hyaluro-
nan (Mazaki et al. 2014). A major advantage of scaffolds from natural polymers
is that these natural materials are more likely to encourage cell growth. Newer
approaches to producing scaffold for biomedical use is the hybrid systems, where
the scaffold incorporates both natural and synthetic materials thus combining the
advantage of both natural and synthetic (Webber et al. 2014).
Design requirement for scaffolds are those which enable uniform cell distri-
bution, nutrients transfer and organized cellular structure development. These
requirements are met and tailored to specific cell by careful selection of poly-
mer formulations and fabrication techniques. Polymers which have been used
in production of scaffolds include chitosan, collagen (Catalina et al. 2013) elas-
tin (Wu et al. 2014), hydrogel foams (Vlierberghe et al. 2014), fibrin and fibrino-
gen (Rajangam and An 2013) and other materials (Gong et al. 2005). Most recent
approaches include use of polymer as matrix for carbon nanotube-based scaffolds
(Serrano et al. 2014) and the use of polymers as coatings for Bioglass-based scaf-
fold materials to improve the mechanical properties (Li et al. 2014a, b, c; Roether
et al. 2002).
There are various types of scaffold depending on their structure and function.
These include: porous, hydrogel, fibrous, acellular, microsphere and polymer-
bioceramic scaffolds. The following sections describe some of these scaffolds and
applications of natural polymers in productions of these scaffolds.

4.2.1 Hydrogel Scaffolds

Hydrogels refer to covalently or non-covalently crosslinked polymer chains form-

ing a highly hydrophilic network with similar structural properties to macromo-
lecular components of tissues and biochemically similar to highly hydrated GAG
components of connective tissues. They can hold up to 99 % of water making
them applicable in promotion of high water contents in tissues. Hydrogels could
be polysaccharide-based, alginate, Ethylene-vinyl alcohol or polyelectrolyte or
thermo responsive hydrogels. Although synthetic polymer-based hydrogels can
be synthesized to precision and have less batch variation, hydrogels from natural
polymers have the advantage of being potentially biocompatible, attaining cell-
controlled degradability and processing intrinsic cellular interaction.
In addition to the general physical requirements for biomaterials used in tis-
sue engineering, hydrogels must show good biological properties such as good
cell adhesion to be applicable as tissue scaffolds. Hydrogels can be designed such
that the degradation rate is well controlled by, for e.g. varying the concentration of
crosslinker or plasticizer (Singth et al. 2009).
96 O. Olatunji

Applications of biocompatible hydrogel scaffolds include bone regeneration,

cartilage wound healing and wound dress. They are also used for drug delivery or
incorporate growth factors to directly act on the newly regenerated tissue to sup-
port cell development and differentiation. Hydrogels are often preferred for scaf-
fold application due to their promotion of cell migration, high water content, rapid
nutrient diffusion and angiogenesis (Dhandayuthapani et al. 2011). Natural pol-
ymers such as collagen, fibrin, alginate, gelatine, fibrin, chitosan and hyaluronic
acid are examples of natural polymers used for producing hydrogels. In a particu-
lar example, hybrid hydrogel scaffolds for application in cartilage replacement can
be produced using chitosan/gelatin hydrogels. This was done using a technique
involving a spinner flask with custom framework for effective nutrients and oxy-
gen transfer (Song et al. 2015).

4.2.2 Fibrous Scaffolds

These are scaffolds made of nanofiber materials. Manipulating polymers at

nanoscale using methods such as electrospinning, self-assembly or phase sepa-
ration tends to achieve fibrous scaffolds which closely mimic the target tissue.
Fibrous scaffolds are particularly preferred due to their high surface-area-to-vol-
ume ratio; a property common to nanostructures, as well as their microporous ori-
entation. This property encourages good cell migration, proliferation adhesion and
differentiation. Applications of fibrous scaffolds include tissue engineering of skin,
vascular neural and musculoskeletal tissues. They are also applied as drug deliv-
ery systems for controlled delivery of proteins, DNA and drugs. Silk fibroin (Mou
et al. 2013), chitosan, collagen, gelatine and hyaluronic acid are examples of natu-
ral polymers used for fibrous scaffolds. As other nanostructures, nanofibres need
to be surface modified using methods such as blending, coating or surface grafting
to prevent agglomeration due to the high surface attraction between the nanoparti-
cles. Another method in the production of fibrous scaffold is to mix active ingredi-
ents to be delivered such as growth factors, drugs and genes into the polymer prior
to production of the nanofibers such that the nanofibers/scaffold can also act as a
delivery vehicle.
A novel approach is to apply a combination of hydrogel and fibrous systems
by coating the fibrous scaffolds with hydrogels. In a particular work, fibrous scaf-
folds made of electrospun polycaprolactone micro- and nanofibers where coated
with chitosan/hyaluronan hydrogel (Deepthi et al. 2015). The scaffold is applied
for rapid regeneration of torn ligaments which is common in young athletes. The
PCL fibres were prepared as either random or aligned fibres via dual electrospin-
ning method shown in Fig. 4.1.
The use of random and aligned fibre was for the purpose of comparing the
effect of fibre alignment on the effectiveness of the scaffold. The electrospun fibres
were then coated with prepared chitosan/hyaluronic acid hydrogel as outlined in
Fig. 4.2.
4  Biomedical Application of Natural Polymers 97

Fig. 4.1  Dual electrospinning of PCL fibres. Obtained with permission from Deepthi et al.
(2015) licence number 3637631134426

Fig. 4.2  Flow chart for production of Hydrogel coated fibrous scaffolds. Obtained with permission
from Deepthi et al. (2015) licence number 3637631134426
98 O. Olatunji

Fig.  4.3  a PCL aligned multiscale fibres. b Top view CH-HA hydrogel on PCL aligned mul-
tiscale fibres. c Cross-section view CH-HA hydrogel on PCL aligned multiscale fibres. d PCL
random multiscale fibres. e Top view CH-HA hydrogel on PCL random multiscale fibres. f Cross-
section view CH-HA hydrogel on PCL random multiscale fibres. Obtained with permission form
Deepthi et al. (2015) licence number 3637631134426

When compared, the hydrogel coated scaffolds showed enhanced protein adsorp-
tion compared to the uncoated PCL scaffolds leading to improved cell viability. In
addition to this, the cell growth pattern encouraged alignment of cells along the
direction of force to make the scaffold function as effectively as the native ligament.
The hydrogel coating on the scaffolds led to better cell attachment and proliferation.
Furthermore, despite the reduced mechanical strength of the random PCL fibres
compared to the aligned fibres, the random PCL fibres showed better cell attach-
ment and proliferation; this is attributed to the increased porosity (Fig. 4.3).

4.2.3 Porous Scaffolds

These are either sponge or foam porous scaffolds made up of evenly distributed
pores often used in tissue engineering applications such as bone regrowth, devel-
opment of vasculature in organs and host tissue growth. They are chosen for these
functions due to their porous nature which mimic ECM (extracllular matrix) archi-
tecture thus promoting cell growth by allowing for cell attraction, proliferation
and differentiation. Polymers which have been used in production of porous scaf-
folds include elastin (Wu et al. 2014), hydrogel foams (Vlierberghe et al. 2014)
and other materials (Gong et al. 2005). Advantages of porous scaffolds include
the ECM mimicking porous structure which encourages cell interaction with the
environment thus providing a framework over which the cells can develop their
own ECM, inhibits the development of adherent contact-inhibit cells and allowing
4  Biomedical Application of Natural Polymers 99

good nutrition distribution in the centre of the structure and limits the formation
of clusters which may lead to cell necrosis; this is by virtue of its pore size which
limits the size of clusters. Foam type porous scaffolds can have either random or
organized patterns which can be determined by the solvent type and separation
conditions (Ma and Zhang 2001). Different cells and tissues have varying require-
ments. Recent research focus on porous scaffold is directed towards developing
more controlled pore size, porosity, orientation, surface-area-to-volume ratio and
crystallinity towards developing more sophisticated and specified tissue scaffolds
(Ma and Zhang 2001; Freiberg and Zhu 2005; Mooney et al. 1994; Wei and Ma
2004; Ouriemchi and Vergnaud 2000).
As an example of porous scaffold production from natural polymers, we take an
example of preparation of silk fibroin/collagen/hydroxyapatite composite scaffolds
as an example. The process of particulate leaching was employed to create the silk
fibroin/collagen/hydroxyapatite composite scaffolds. The composite combined the
sinterability and enhanced densification property of hydroxyapatite hence it’s good
mechanical properties, with collagen’s ability to form a good ECM and enhance
cell adhesion and migration together with the low cost, biocompatibility, water
vapour permeability, biodegradability and minimal inflammatory reaction of silk
fibroin. Thus, making up a composite material with desirable properties for bio-
medical application—in particular scaffold production (Mou et al. 2013).
The particulate leaching method used in this particular example employs a one-
step fabrication method which is relatively simpler than conventional particulate
leaching processes which have been used for scaffold production. The method
as illustrated in Fig. 4.4 is as follows. Sodium Chloride particles were mixed
with hydroxyapatite particles with a dimension of 150 nm by 20 nm needle-like
structures at 99 % purity. This was closely packed into a 20 mL plastic syringe
­followed by adding a mixture consisting of 6 % v/v solution of silk fibroin and

Fig. 4.4  Illustration of stages for production of scaffolds by particulate leaching process. Image

obtained with permission from Mou et al. (2013) licence number 3637080927038 original
­publisher, Elsevier
100 O. Olatunji

6 % w/v collagen. The mixture was then pressed down with the syringe piston
and in the process excess materials consisting of water, excess protein solution air
were released from the syringe tip. The material left in the syringe tip, which is a
composite of silk fibroin, collagen, hydroxyapatite and sodium chloride was left at
room temperature for 24 h after which it was removed and crystalized using etha-
nol (70 % v/v) for 30 min after which it becomes insoluble in water. The remain-
ing salt and excess unbounded hydroxyapatite was removed by repeated washing
in ultra water. The porous scaffold is thereby formed.
The composites formed showed good blending and uniform distribution of the
silk fibroin, collagen and hydroxyapatite. A uniform scaffold was formed with
good three-dimensional structure and controllable pore size (decreased sodium
chloride concentration resulted in decreased pore diameter) and interconnected
porosity. The scaffold significantly promoted Human Osteosarcoma MG-63 cells
proliferation as shown in the confocal laser scanning microscope (CLSM) shown
in Fig. 4.5 and taking a count of viable cells on the scaffolds following incubation
period of 0, 1 and 3 days. The properties of the scaffold such as porosity, shape of
pores and water uptake was affected by the sodium chloride particle size and the
content of the collagen, silk fibroin and hydroxyapatite. As such, this method for
producing porous scaffold can achieve scaffolds with controllable pore size and
interconnected porosity as well as good cell proliferation (Mou et al. 2013).
Porous scaffolds have also been prepared from natural polymers using other
methods such as freeze drying. For example, porous scaffold produced from a
blend of chitosan, silk fibroin and hydroxyapatite. The mixture was stirred by a
magnetic stirrer for a day followed by sonication for 10 min. The suspended mix-
ture was then poured into a 40 mm by 90 mm mould made of polytetraflouro-
ethylene and frozen to −20 °C for 24 h. This was followed by lyophylization for
another 24 h after which the dried samples were separated from the mould and then
neutralized in sodium hydroxide aqueous ethanolic solution 8:2 vol.% for 3 h. This
was followed by washing in ultra pure water and crosslinking with 2.5 % sodium
tripolyphosphate solution for 3 h to further stabilize the chitosan. 3D scaffolds

Fig.  4.5  CLSM photographs showing MG-C6 cell growth of the silk fibroin/collagen/
hydroxyapatite scaffolds after culturing at a day 0, b day 1, c day 3. Image obtained with permis-
sion from Mou et al. (2013) licence number 3637080927038 original publisher, Elsevier
4  Biomedical Application of Natural Polymers 101

were eventually obtained following an additional cycle of freeze drying and lyoph-
ilisation (Lima et al. 2013). The scaffolds achieved using this method showed good
biocompatibility without any cytotoxic effect, they also allowed good cell growth
and differentiation.

4.2.4 Acellular Scaffolds

These are produced by decellularizing a tissue, i.e. removing all cellular compo-
nents of the tissue, leaving behind a collagen-rich matrix which will act as the
structural frame of the newly growing tissue. The removal can be either by chemi-
cal or mechanical processing but without causing damage to the ECM of the origi-
nal tissue. This is then followed by cell implantation; the decelularized matrix then
gradually degrades and is replaced by the new cells. Naturally derived polymers
can also be used for acellular scaffolds. This is done by coating the decellularized
scaffold with the naturally derived materials such as a biopolymer to give mechani-
cal strength and the decelularization process achieves a matrix which is a physi-
ological replica of the naturally existing tissue. The advantage of this approach
to scaffold production includes; decellularizing achieves a tissue matrix structure
which is a replica of the original tissue, retention of the cell adhesion ligands and
architecture or the native ECM, reduced tenencies of an immune response as decel-
lularization process has removed cellular components and the decellularized tissue
has similar biomechanical properties of the native tissue (de Blacam et al. 2011).
Some acellular scaffolds approved for human application as scaffolds include
those from accellularized heart valves, small intestine submucosa and urinary
bladder. Human collagen-based scaffolds can also be achieved from acellular adi-
pose matrix (Sano et al. 2014).

4.2.5 Gelatin-Based Scaffolds

Scaffolds from various forms of gelatine have been reported in recent years.
Gelatin is particularly attractive in tissue engineering due to its ability to keep
cells in a gel state at low temperature, amidst its other attributes such as ease of
modification, cost effectiveness and biocompatibility as it naturally occurs in the
ECM. Gelatin however has a major limitation posed by its relative mechanical
weakness. The mechanical, morphological and bioactive properties of gelatin can
be controlled by crosslinking and/or including particulate carriers incorporating
either drugs or growth factor which are necessary to encourage the growth of tis-
sue (Nazeer and Sri Suganya 2014; Zhang et al. 2011; Nandagiri et al. 2011; Wu
et al. 2010). The possibility of tuning the pore size and distribution makes gela-
tine-based porous scaffolds applicable in a variety of applications.
102 O. Olatunji

Gelatin scaffolds can achieve pore sizes of between 50 and 750 µm with recent
studies revealing potential for achieving smaller pore sizes of between 30 and
350 µm with improved interconnectivity by crosslinking with zeolite using formal-
dehyde (Ninan et al. 2013). Crosslinking with other polymers such as hyaluronic
acid (Zhang et al. 2011), starch and chitosan have been shown to lead to improved
mechanical properties on the scaffolds and incorporation of nanoparticules such
as PLGA (Nandagiri et al. 2011) and hydroxyapatite (Sundaram et al. 2008) have
resulted in biocomposite porous scaffolds with enhanced mechanical proper-
ties. Gelatin–chitosan porous scaffold are examples used in porous scaffold for
bone tissue regeneration, combining the flexible gel property of gelatine with the
cell adhesion, reinforcement and ionic property of chitosan to produce a porous
scaffold with sufficient physiochemical and biomechanical properties. Gelatin–
chitosan porous scaffolds incorporating PLGA nanoparticles showed decreased
pore size, scaffold dissolution rate, water uptake while compression modulus was
increased and biocompatibility was unaffected (Nandagiri et al. 2011). Hyaluronic
acid has also been crosslinked with gelatine showing tendency to produce porous
scaffolds with tuneable properties such as mechanical strength, porosity, swelling
and degradation rate by varying the concentration of the hyaluronic acid.
A network composite of hydroxyapatite/chitosan–gelatin have been used to pro-
duce three-dimensional porous scaffolds with uniform pores in the microscale with
good biomimetic properties. The scaffold formed showed cell adhesion, proliferation
and induced expression of new osteoblast cells (Hule and Pochan 2007). Porous gela-
tine scaffolds produced by freeze drying and mineralized by coating with hydroxyapa-
tite to further control degradation rate have been shown to be effective scaffolds for
protecting encapsulated drugs or growth factors in tissue engineering. Biological stud-
ies showed the mineralized porous gelatine scaffold to demonstrate good cell prolif-
eration and differentiation of osteoblast cells which is suitable for tissue engineering
(He et al. 2012). More recent techniques employ a blend of chitosan—collagen–gela-
tin in a multistep process involving freeze drying and use of genipin as a stabilizer in
producing porous tissue engineering scaffolds (Gorczyca et al. 2014).
The mechanical properties and morphology of porous gelatine scaffold can also
be controlled by varying the fabrication conditions. Example of such approach is the
introduction of cryogenic conditions to improve the mechanical property of nano-
hydroxyapatite–gelatin porous scaffold (Swain and Sarkar 2013). Photo chemically
modified gelatine scaffolds have also been applied in corneal tissue regeneration.
Recent years have seen developments in chemical modification of gelatine scaf-
folds using visible light. This has led to improvement of biomechanical properties
as well as specificity and minimizing invasiveness of scaffold application. Gelatin
incorporated with furfuryl isocyanate and furfurylamine using photo-cross-link-
ing with Rose Bengal to produce hydrogel scaffolds used for applications such
as cartilage replacement. An area of tissue engineering where such hydrogel gela-
tine scaffolds have become applicable is in the scaffold healing of injured knee
(Mazaki et al. 2014). This type of injury poses a challenge as it is an osteochon-
dral injury which results in damage to both the articular cartilage which has lim-
ited healing capabilities and the underlying subchondral bone which without
4  Biomedical Application of Natural Polymers 103

protection of the articular cartilage continues to degenerate. Since the articular car-
tilage provides cushioning to protect the underlying subchondral bone, failure to
regrow the articular cartilage will further wear the underlying bone which poten-
tially results in more serious medical problems such as osteoarthritis and osteo-
arthrosis. A treatment approach is to use a scaffold to regrow new articular tissue
at the location thus preventing further damage to the subchondral bone. Natural
polymers such as gelatin have had some applications here.

4.2.6 Natural Polymers in Carbon Nanotube-Based

Scaffolds

Carbon nanotubes (CNTs) have demonstrated properties which make them very
applicable in biomedical applications such as production of scaffolds. Natural
polymers play significant role in production of 3D scaffolds incorporating CNTs.
Although CNTs are attractive options for scaffold production due to their excep-
tional properties such as thermal stability, mechanical properties, electrical con-
ductivity, versatile structure and ease of mass production amongst other properties
(Serrano et al. 2014) which make them applicable in scaffold production. Natural
polymers play a significant role in production of CNT-based scaffolds with improved
since despite their favourable properties, scaffolds based solely on CNTs face limi-
tations which are mainly in the area of biocompatibility and mechanical properties.
Combination with natural polymers tend to biocompatibility and introduce more
desirable mechanical properties (Pandey and Thostenson 2012; Sahoo et al. 2010).
In such approach, CNTs are generally used as reinforcements in natural pol-
ymer-based composites from which scaffolds are then fabricated using methods
such as freeze casting, electrospinning and gel forming. Natural polymers used fro
such include gelatin, chitosan, alginate, silk and collagen (Shin et al. 2012; Olivas-
Armendariz et al. 2010; Yildirim et al. 2008; Ayutsede et al. 2006; Hirata et al. 2011).
These have achieved scaffolds with controllable and interconnecting pore dimensions.
In a particular example multiwalled CNTs reinforced chitosan at 89 % wt CNT
were used to produce scaffolds with evenly distributed interconnecting porosity using
the ice segregation-induced self-assembly (ISISA) method (Serrano et al. 2014). This
method achieves macroporous, well-aligned microchannels with well-patterned mor-
phology. It involves dipping the composite in a liquid nitrogen bath at constant rate to
achieve unidirectional freezing. Such scaffolds are applicable for bone tissue regen-
eration as they show good conductivity as a result of good CNT interconnection.
For instance when recombinant human morphogenetic protein 2 (rhBMP-2) were
implanted in mice, ectopic bone formation was observed (Abarrategi et al. 2008).
In other cases regeneration of osteoblast cells was encouraged when implanted into
scaffold made from chitosan incorporating CNTs (Nardecchia et al. 2012).
Similar approach has been used to fabricate scaffolds from CNT reinforced
scaffolds of gelatine combined with chondroitin sulphate, chitosan combined with
hydroxyapatite and hyaluronic acid hydrogels. These formed scaffolds with good
104 O. Olatunji

Fig.  4.6  a MWCNT films by CVD. b Porous 3D chitosan/MWCNT scaffolds by ISISA

process (Serrano et al. 2014). Reproduced with permission from Elsevier, licence number
3640171060983

pore characteristics and mechanical properties as well as promotion of cell growth.

Figure 4.6 shows images of CNTs produced by Chemical Vapour deposition and
CNT reinforced chitosan produced by ISISA. Electrospun CNT-based scaffolds
incorporated into natural polymers are also produced from natural polymers such
as silk fibroin, agarose, zein and cellulose acetate (Serrano et al. 2014).

4.3 Wound Healing

There are occurrences of sever wounds and burns which pose some challenges
in clinical care. Wound healing products are required to protect the injury during
the four stages of healing (haemostasis, inflammation, proliferation and matura-
tion) (Lee et al. 2015), from infection and physical contact which may lead to fur-
ther damage of the injured area or cause pain to the patient. The wound healing
material also enhances healing and repairs of the injured tissue. Natural polymer
such as collagen, gelatin, chitin, chitosan, heparin, alginates and silk fibroin are
widely used in wound healing application as they possess desirable properties to
this effect (Dreifke et al. 2015). An effective wound healing material should pro-
vide a conducive environment for cell proliferation, migration and differentiation
and encourage re-epithelialization (Mogosanu and Grumezescu 2014). The ulti-
mate target in wound healing is for the injured area to be completely returned to its
native form without visible scars or pain.
Materials used in wound healing applications must meet certain requirements.
For example, tissue adhesives used for wound closure following surgical or hemo-
static procedures are required to be cost effective, biocompatible, biodegradable,
possess good binding strength, allow simple application and cause no toxic effect
on the patient (Lee et al. 2015; Thirupathi et al. 2013; Hadba et al. 2011). Natural
polymers find good applicability in wound healing as tissue adhesives, membrane
fibres or gels for wound healing. They are used either solely or in combination
with other synthetic or natural polymers.
4  Biomedical Application of Natural Polymers 105

Chitin and chitosan have shown good prospects in wound healing application
(Minami et al. 2014; Antunes et al. 2015). More recently nanofibrils of chitosan
and chitin have been applied in wound healing (Muzzarelli et al. 2014; Izumi et al.
2015), although showing varying effectiveness. Talymed® is an example of com-
mercially available wound healing product which uses the chitosan nanofibril tech-
nology. It is applied in the healing of venous leg ulcers showing improved healing
effect compared to standard treatments (Kelechi et al. 2012). Other reports show
nanofibers of chitosan affected the antibacterial activity and cell attachment and
proliferation in murine fibroblasts in vitro (Cai et al. 2010).
In a novel approach (Izumi et al. 2015), superficially deacetylated chitin are
used. Unlike chitosan of chitin nanofibrils, SDACNFs tend to induce better re-
epithelium and fibroblast and collagen proliferation in the skin tissue. As shown
in Fig. 4.7, the wound healing was much more advanced on day 8 for SDACNF
group than the other groups (NT-non treated, Water treated, Chitin treated, CNF—
Chitin nanofibrils, CSNF—Chitosan nanofibrils).
Furthermore the SDACNF group was the only group which showed re-epitheli-
zation at day 4 in the histographs shown in Fig. 4.8. SDACNFs have the surfaces
of the chitin nanofibrils deacetylated to form chitosan while the cores remain as
chitin crystals (Fan et al. 2010; Izumi et al. 2015).
Another polymer that has been recently explored in novel approach to wound
healing application is poly lactic acid which is commonly derived from the natural
polymer, starch. To achieve a wound healing material with improved biocompat-
ibility and reduced toxicity, polylactic acid is blended with allyl 2-cyanoacrylate
which is a synthetic polymer commonly used as tissue adhesive (Lee et al. 2015).

Fig. 4.7  Healing of circular excision wound model on mice after day 8 for each group. Image
obtained from Izumi et al. (2015) with permission from Elsevier licence number 3641300131392
106 O. Olatunji

Fig. 4.8  Histographical images showing the various sections in the skin wound healing of mice
with the circular excision wound model after day 4, for different samples showing sections of
scab(s), re-epithelization (RE) and neovascularization (NV). Image obtained from Izumi et al.
(2015) with permission from Elsevier licence number 3641300131392

Fig. 4.9  Comparison of Collagen content for tissue treated with different tissue adhesives for
wound healing. Image obtained from Lee et al. (2015) with permission from Elsevier. License
number 3641351146064

Tissues treated with tissue adhesives with PACA/PLLA showed better tensile
properties indicating better collagen formation hence wound healing when com-
pared to two other commercial wound healing tissue adhesives, Dermabond® and
Histoacryl®. PACA/PLLA tissue adhesives showed higher collagen formation at
day 4 compared as shown in Fig. 4.9. In addition to this it demonstrated better
biocompatibility.
Wafers of lyophilized composite of sodium alginate SA/GE with 1 % silver
sulfadiazine drug loading (0.1 % w/w) can also be applied in healing of chronic
wounds (Boateng et al. 2015). At a 75/25 % sodium alginate/gelatin composi-
tion, such wafers showed good mechanical properties, uniformity, mucoadhesive-
ness, hydration and good drug release kinetics which makes them applicable in
4  Biomedical Application of Natural Polymers 107

Fig. 4.10  Digital photographs of BL SA/GE wafers a 100/0, b 75/25, c 50/50, d 25/75, e 0/100

and SSD loaded SA/GE wafers f 100/0, g 75/25, h 50/50, i 25/75, j 0/100. Image obtained from
Boateng et al. (2015) with permission from Elsevier, Licence number 3641440617065

wound healing. Although alginates have been widely applied in wound healing
(Mogosanu and Grumezescu 2014), this is a novel approach which is aimed at
improving the hydration induced gel dehydration of alginate-based wound dress-
ing by blending with gelatin. Figure 4.10 shows the wafers formed at varying
composition of sodium alginate and gelatin.

4.4 Natural Polymer Implants

Implants are often a preferred option for controlled delivery of active pharma-
ceutical ingredients (APIs) into the body as a means to avoid the limitations and
adverse effects which may occur in other forms of drug delivery such as first pass
metabolism leading to low bioavailability in oral and discomfort and pain associ-
ated with intravenous injections as well as generally increase risk of side effects
associated with bolus systemic delivery.
Applications of natural polymer in implants are of much interest for similar
reasons as in every other biomedical application (Ivanova et al. 2014). Since these
are materials which remain embedded in the body for long periods, it is important
that they are biocompatible and remain functional throughout the duration they
will remain embedded in the body until they are removed or are to degrade into
the body rerelease not toxic, biocompatible degradation products which can be
harmlessly eliminated from the body.
Drug eluting implants are implants which are loaded with APIs should meet the
requirement of allowing drug loading to desired concentration and release the drug
when implanted at controlled rate (Guzman-Aranguez et al. 2013; Siepmann et al.
2012). Polymer-based drug eluting implants can be fabricated using methods such
as hot melt extrusion, solvent casting, coating or soaking of the polymer in the API
(Loxley 2012; Iqbal et al. 2013; Zurite et al. 2006).
108 O. Olatunji

Recent method of loading API unto polymeric drug eluting implants is the
supercritical CO2 assisted impregnation process (Champeau et al. 2015). This
method is introduced as a measure to address the drawbacks of the other afore-
mentioned methods of producing drug loaded polymeric implants. These draw-
backs are mainly high processing temperature requirement which could potentially
damage temperature sensitive drugs such as protein-based drugs, and need for
organic solvents which then necessitate numerous purification stages.
The supercritical CO2 impregnation technic has been applied in loading of vari-
ous natural polymer-based implants which are produced from natural polymers
such as chitosan, agarose, cellulose, collagen and polylactic acid. The process is
based on the unique properties of CO2 at its supercritical state which enhances
the solubility of APIs in manufactures polymers. The supercritical CO2 causes the
polymer to swell thereby increasing its permeability; it also dissolves many APIs
making them diffuse better into the polymer matrix. The process can be carried
out at relatively low temperature (31 °C and 73.8 bar) and does not require addi-
tional process for solvent removal as non is used (Champeau et al. 2015; Kikic and
Vecchione 2003). Table 4.1 lists some natural polymers which have been applied
as implants and the API which was loaded on the implant.
Natural polymers can be applied as coatings on implant for purposes such as
improving biocompatibility, modifying the release profiles of the implant (Green
et al. 2009) or improving the stability, bioactivity and resistance to corrosion
(Ahmed et al. 2013) while retaining the properties of the main implant material.
In an example implants produced with nanoscope polyelectrolyte multilay-
ers (PEMs) of hyaluronic acid/chitosan blends for delivery of chitosan imidazole
binded siRNA (Small interfering RNA) nanoplexes (Hartmann et al. 2013). The
assembly is illustrated in Fig. 4.11.
Small Interfering RNAs are bioactive molecules which play important role in
therapeutic mediation of enzymatic cleavage of mRNA of targeted cells such as

Table 4.1  Examples of natural polymers used in implants

Polymer API/implant References
Chitosan Flurbiprofen Braga et al. (2008)
Timolol maleaic Braga et al. (2008)
Tymol Dias et al. (2011)
Quercetin Dias et al. (2011)
Dexamethason Duarte et al. (2009)
Vycomycin Yang et al. (2013)
Hyaluronic acid/chitosan Chitosan Imidazole/siRNA Hartmann et al.
multilayer coating nanoplexex (2013)
Chitosan/carbonnanotube Titanium implant Ahmed et al. (2013)
Collagen/cellulose Juca extract Dias et al. (2013)
Agrose Thymolol Dias et al. (2011)
Querecetin
Poly (Lactic acid) Ibuprofen Ma et al. (2010)
Acetylsalicylic acid
4  Biomedical Application of Natural Polymers 109

Fig. 4.11  Structure of Hyaluronic acid/chitosan coated implant for delivery of siRNA nano-

plexes Obtained from Hartmann et al. (2013), with permission from Elsevier, licence number
3642361195751

cancer cells (Meister and Tuschl 2004; Fire et al. 1998). This is a technique being
investigated for biomedical applications such as cancer therapy and viral infec-
tions (Brower 2010). The aim of siRNA implant is to release siRNA from the
implant, attach the siRNA to target cells to allow cell destruction through enzy-
matic cleavage of mRNA. The implant should therefore effectively incorporate the
siRNA nanoplexe, maintain its integrity and deliver it to target cells.
Chitosan is particularly of interest in this application due to its electrostatic
attraction to nucleic acids allowing it to form stable chitosan siRNA nanoplexes
(Hartmann et al. 2013). Furthermore, combination with hyaluronic acid a poly-
anion to obtain a polyelectrolyte multilayer system using layer by layer assem-
bly techniques which allow alternative adsorption of positive and negative charged
polyelectrolytes to form a multilayer with diverse functionality which is essential
in such biomedical application.
The use of chitosan and hyaluronic acid composite as drug release coatings on
the implant material which could be made from another polymer material such as
polydiocanone (Ribeiro-Resende et al. 2009) it to mitigate against the tendency of
the nanoplexe to affect the stability of the implant and also to improve cell adhe-
sion and uptake of nanoplexes by the cell. While other polyelectrolytes such as
poly (sodium-4-Styrene-Sulfonate) and poly (l-glutamic acid) cause destabiliza-
tion of nanoplexes Chitosan Polyelectrolyte PEM does not (Hartmann et al. 2013).
Chitosan coatings can also be applied for surface modification of titanium
implants to address the issue of corrosion and biocompatibility which is some-
times seen in titanium implants. Although other surface modifications exists such
as thermal oxidation and hydrothermal synthesis and ion implantation as well as
use of other bioactive coating such as hexamethyldisilazane and calcium phos-
phate, chitosan provides a potential alternative as it has been widely used in vari-
ous biomedical applications. In a recent approach chitosan reinforced with carbon
nanotubes showed enhanced toxicity resistance and passivation compared to other
coatings (Ahmed et al. 2013).
Cardiovascular devices such as stents (Iqbal et al. 2013) and heart valves are
implanted into the heart for controlled drug delivery targeted at the cardiovascular sys-
tems or to play functional role such as controlling the heartbeat or sending out signals
in case of potential or occurring cardiovascular emergencies (Venkatraman et al. 2008).
110 O. Olatunji

4.5 Conclusion

In this chapter, we have explored how natural polymer-based materials are applied
in various aspects of biomedical industry. Example cases of natural polymers which
play prominent roles such as chitosan, hyaluronic acid, silk fibroin and gelatin are
discussed. Innovative approaches to producing natural polymer-based biomedi-
cal moieties are also discussed. These include supercritical CO2 impregnation of
implants, particulate leaching to produce porous scaffolds and superficial deacetyla-
tion of chitin to produce nanofibrils for wound healing are discussed. We also look at
the role natural polymers play in advancing the particular biomedical application by,
for e.g. improving biocompatibility, bioactivity and reducing toxicity. Natural poly-
mers generally show good applicability in present and future biomedical industry.

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Chapter 5
Application of Natural Polymers in Food

Marilyn Rayner, Karolina Östbring and Jeanette Purhagen

5.1 Introduction

In this chapter, the application of natural polymers is considered in the context of

formulated foods. Basically, all food contains macromolecules, and almost all of
these macromolecules are polymers of some kind. Polymer molecules in their sim-
plest form are linear chains of covalent bonded monomers. The number of times
these monomers are repeated along the polymer chain is the degree of polym-
erization. Most polymers vary in degree of polymerization and thus molar mass.
If several monomers are involved then the structure can be more complicated.
Moreover, polymers can be branched, and the individual monomers can also pos-
sess different attributes, such as charge (i.e., polyelectrolytes) and hydrophobic-
ity (amphipathic polymers), further adding to the complexity. These higher order
structures are what often give polymers their function in food (Walstra 2003).
Most foods are made up of the three main types of naturally occurring poly-
mers, primarily polysaccharides (i.e., starches, celluloses) and polyamides (pro-
teins), as well as small amounts of polynucleotides (DNA, RNA) found in cellular
material.
Polynucleotides (or nucleic acids), i.e., DNA (deoxyribonucleic acid) and RNA
(ribonucleic acid) are linear heteropolyelectrolytes containing four types of mono-
mers. Each monomer unit within the polymer chain has three components: a sugar

M. Rayner (*) · K. Östbring · J. Purhagen 

Department of Food Technology, Engineering, and Nutrition, Lund University,
P.O. Box 124, 2100 Lund, Sweden
e-mail: marilyn.rayner@food.lth.se
J. Purhagen 
Perten Instruments AB, Garnisonsgatan 7a, 254 66 Helsingborg, Sweden

© Springer International Publishing Switzerland 2016 115

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_5
116 M. Rayner et al.

(either deoxyribose in DNA or ribose in RNA), a phosphate, and a base. The back-
bone is constant in DNA and RNA, however, the bases vary between four pos-
sible. Adenine (A), guanine (G), cytosine (C), and thymine (T) in DNA, and A,
G, C, and uracil (U) for RNA (Berg et al. 2002). This sequence of bases uniquely
characterizes a nucleic acid and represents a form of linear biological information.
Although DNA and RNA are present in all cells and thus in many foods materials
based on meat and plant tissues, their concentrations are far too small to affect the
food’s physicochemical properties and will not be discussed further in this chapter.
Proteins are complex linear heteropolyelectrolytes containing a unique
sequence of up of 20 different amino acids monomers, having highly diverse
configurations and reactivity with respect to charge, hydrophobicity, and aro-
matic structure. Proteins typically have a degree of polymerization of around 103
and have numerous biological functions in living cells and organisms. As a food
ingredient, in addition to a source of amino acids for our own metabolism, pro-
teins provide both structure and function. They can create gels, increase viscosity
and water holding capacity, as well as generating and stabilizing emulsions and
foams. Despite their functionality, the higher price of proteins compared to other
natural biopolymers (especially with respect to starches and celluloses) has limited
their technical application (VâniaReginaNicoletti 2012). Major protein ingredients
include: gelatin, milk proteins, egg proteins, and plant proteins.
Polysaccharides are heteropolymers of sugars and derived components. They
can be linear or branched, and several of them are polyelectrolytes. The degree of
polymerization of polysaccharides is generally 103–104. The main biological func-
tions are ‘‘nutritional’’ as energy stores for metabolism (primarily starch in plants,
glycogen in animals) and ‘‘building material’’ (such as cellulose in plants and chi-
tin component of the cell walls of fungi and in the exoskeletons of arthropods such
as crustaceans). The latter are called structural polysaccharides, which occur in a
great variety of types and mostly form mixed and highly complex structures.
In the scientific and trade literature, proteins and polysaccharides are also often
referred to as “hydrocolloids.” There are a number of different natural sources of
commercially important hydrocolloids as given in Table 5.1.

Table 5.1  Sources of commercially important hydrocolloids used in the food industry (Williams

and Phillips 2009)
Botanical Plants Starch, pectin, cellulose
Trees Cellulose
Tree gum exudates Gum arabic (acasia), gum tragacanth, karaya gum
Seeds Guar gum, tara gum, locust bean gum, fenugreek
gum
Tubers Konjac mannan (glucomannan), potato starch
Algal Red seaweed Agar, carrageenan
Brown seaweed Alginate
Microbial Xanthan gum, dextran, gellan gum, cellulose
Animal Gelatin, caseinate, whey protein, chitosan
5  Application of Natural Polymers in Food 117

Protein and starch are major component of foods in general, and as such impor-
tant sources of macro nutrients. However, in this chapter, the focus will be on
natural polymers as food additives and ingredients in food formulations having a
specific function beyond basic nutritional value. These specific functions of natu-
ral polymers added to foods can be classified into two main categories:
• The creation and stabilization of food microstructures: e.g., gelling, thicken-
ing, stabilization of emulsions, and foams, as well as processing aids, such as
cyroprotectants to improve freeze thaw stability, drying aids, and encapsulating
material.
• Additional physiological and biological functions: e.g., functional foods with
specific health claims such has reducing blood cholesterol levels, increasing
satiety, and improved bioavailability, as well as antioxidative and antimicrobial
activity for preservation purposes.
This chapter will discuss the various types of natural polymers in food primarily
from the perspective of their function in a food product formulation, rather than
discussing the separate polymers by chemical structure or origin. Details on clas-
sification, processing, and extraction methods are provided in dedicated chapters
in this book (Chaps. 2, 3, and 4, respectively). In addition to function and use of
natural polymers in food, this chapter will also touch on regulatory and market
aspects of these additives and ingredients in food products.

5.2 Creation and Stabilization of Food Microstructures

If we consider the creation and stabilization of food microstructures from the per-
spective of the functional roles natural polymers play in these systems, we can
roughly classify them into three groups: (i) emulsion stabilizers, (ii) thickeners,
and (iii) gelling agents. Although, it is also good to note that a given natural pol-
ymer may in fact be providing several of these functions concurrently (Giannou
et al. 2014). An overview of the structure and function of some key natural pol-
ymers in generating and stabilizing food microstructures are presented briefly in
Table  5.2 and applications of these natural polymers by product types are pre-
sented in Table 5.3.
The main role that natural polymers play when used in formulated food is to
create and maintain texture and microstructure (Aguilera et al. 2000). Further
quality improvements of existing foods and the creation and formulation of new
products to satisfy the expanding consumers’ demands in the near future will
be based largely on interventions at the microstructure level. This is because
the majority of factors that critically participate in transport properties, physical
and rheological behavior, textural and sensorial traits of foods are elements and
phenomena that are occurring on a scale below 100 µm (Aguilera 2005). These
microstructural elements are often based on natural polymers and their function
in formulations. Typically, they are dispersed in water creating viscous solutions,
118 M. Rayner et al.

Table 5.2  Some key natural polymers in generating and stabilizing food microstructures

Type M1 (Da) Functions Comments
Starch amylose 2 × 105–107 • Stabilizer Starch gelatinization, the
Starch amylopectin (freeze/thaw,ordered crystalline regions
Modified starches heat, acid, undergo melting, permitting
Chemical: crosslinked, shear) granule swelling and gel
substitution (example acetate, • Thickener formation, this can be fol-
phosphate and sodium octenyl • Moisture lowed by recrystallization and
succinate), dextrinization, control formation of helix structures.
oxidation and thinning • Texturizer Modifications can make
Physical: pre-gelatinized, • For particle the starch cold swelling or
granular and agglomerated suspension non-swelling.
• Emulsifier Different ratios of amylose
(modified and amylopectin affects the
starch) product characteristics.
Thermally irreversible,
opaque gels formed on cool-
ing (modified starch).
Methylcellulose 2 × 104–4 × 105 • Stabilizer Semi-soluble polymer with a
Carboxymethylcellulose (CMC) 105–106 • Thickener wide range of viscosities.
Hydroxypropylmethylcellulose • Water retention Viscosity increases with tem-
(HPMC) perature (gelation may occur).
The molecules associate on
heating due to hydrophobic
interaction of methyl groups.
Methylcellulose form strong
gels at elevated temperature
while HPMC forms weak
gels, the gels are reversible
and not influenced by the
addition of electrolytes or pH.
CMC gives high viscosity but
it is reduced by the addition
of electrolyte and low pH.
Pectins 4 × 104–105 • Stabilizer HM pectin forms gels at low
High Methoxyl (HM) • Thickener pH (2.5–3.5) in the presence
Low Methoxyl (LM) • Gelation of high sugar concentration
• Protein (>55 %). This combination
protector reduces electrostatic repul-
sions between chains. Chain
association is also encouraged
by reduced water activity.
LM pectin forms gels in the
presence of divalent cations,
notably calcium at low pH
(3–4.5). The molecules are
crosslinked by the cations.
Sugar beet pectin is
non-gelling—emulsification.
(continued)
5  Application of Natural Polymers in Food 119

Table 5.2  (continued)
Type M1 (Da) Functions Comments
Gum Arabic (Acacia) 4 × 106–107 • Stabilizer Newtonian behavior with
• Thickener low viscosity at concentra-
• Emulsifier tions <40 %, pseudoplastic at
• Encapsulating higher concentrations.
agent Cold and hot water soluble
• Texturizer for concentrations <50 %.
• Coating Shear thinning at low shear
agent rates (<10/s).
Near Newtonian behavior
above 100/s of shear rate.
Rheology strongly affected by
pH and electrolyte.
Temperature and high shear
stable.
Gum Tragacanth 8.4 × 105 • Stabilizer Swells rapidly in cold or hot
• Thickener water to form highly viscous
• Emulsifier dispersions, up to 4000 mPas
at 1 % solids.
Pseudoplastic behavior.
Acid resistant and viscosity
stable at pH 2–10.
Karaya gum 16 × 106 • Stabilizer Producing a viscous colloidal
• Thickener sol when dispersed in water
• Emulsifier due to that it adsorb water and
swell to more than 60 times
the original volume. The
swelling behavior is caused
by the presence of acetyl
groups in its structure.
Viscosities are higher when
the gum is dispersed in cold
water than in hot water.
Galactomannans • Stabilizer Very high low shear viscosity
(Galactose: Mannose ratios) • Thickener and strongly shear thinning.
Locust bean gum 1:4 • Texturizer Not influenced by the pres-
Tara gum 1:3 • Water ence of electrolyte but can
Guar gum 1:2 retention degrade and lose viscos-
Fenugreek gum 1:1 ity at high and low pH and
when subjected to high
temperatures.
Locust bean gum: Gels
formed after freezing.
Galactose deficient regions
associate.
Tara gum is soluble in cold
water and is often mixed with
other hydrocolloids.
(continued)
120 M. Rayner et al.

Table 5.2  (continued)
Type M1 (Da) Functions Comments
Konjac mannan/glucomannan 2 × 105–2 × 106 • Thickener Cold swelling.
• Gelation Forms highly viscous disper-
• Dietary fiber sions which are not influenced
• Water binder by addition of salts.
• Texturizer Forms thermally irrevers-
ible gels with alkali. Alkali
removes acetyl groups along
the polymer chain and chain
association occurs.
Agar • Stabilizer Heat reversible gel formed on
• Thickener cooling. Molecules undergo a
• Gelation coil-helix transition followed
by aggregation of helices.
Gives a firm and brittle gel to
body/mouthfeel.
pH stability 2.5–10.
Carrageenans 104–106 • Stabilizer Forms reversible gels on cool-
Kappa • Thickener ing in the presence of salts in
Iota • Gelation an aqueous environment. The
Lambda presence of salt reduces electro-
static repulsions between chains
promoting aggregation.
Gelling ability is seen for
carrageenan that forms helical
structures.
pH stability 4–10.
Kappa Carrageenan gives firm,
brittle structure and syneresis.
Iota Carrageenan gives elastic
and soft structure without
syneresis.
Lambda-Carrageenan: no gela-
tion, thickening, gives body.
Alginate • Stabilizer Cold soluble and gelling.
High M • Thickener Heat stable and shear revers-
High G • Gelation ible firm gel, pH stability
• Emulsifier 4–10.
Gels formed with the addition
of polyvalent cations notably
calcium or at low pH (<4).
Molecules crosslinked by the
polyvalent ions.
Propylene Glycol Alginate
(PGA): surface active ingredi-
ent, cold soluble, non-gelling,
pH stability 3.5–10.
(continued)
5  Application of Natural Polymers in Food 121

Table 5.2  (continued)
Type M1 (Da) Functions Comments
Xanthan gum 3 × 105–107 • Stabilizer Solutions have a thixotropic
• Thickener behavior.
Gels are formed at high
concentration or in the pres-
ence of plant galactomannans
such as locust bean gum on
cooling. Xanthan and the
polymannan chains associ-
ate following the xanthan
coil-helix transition. For
locust bean gum the galactose
deficient regions are involved
in the association.
Very high low shear viscosity
(yield stress), highly shear
thinning, maintains viscosity
in the presence of electrolyte,
over a broad pH range and at
high temperatures.
Gellan gum 1 × 106 • Protein Gels formed on cooling in the
Low Acyl protector presence of salts. Molecules
High Acyl • Suspender undergo a coil-helix transition
followed by aggregation of
helices. Salts reduce elec-
trostatic repulsions between
chains and promote aggrega-
tion. Multivalent ions can act
by crosslinking chains.
Low acyl gellan gels are
thermoreversible at low salt
concentrations but non-
thermoreversible at higher
salt contents (>100 mM)
particularly in the presence of
divalent cations.
Gelatin 3 × 104–106 • Stabilizer Produces transparent gels
• Thickener with the highly desirable abil-
• Gelation ity to melt in the mouth. Gel
formed on cooling. Molecules
undergo a coil-helix transition
followed by aggregation of
helices.
Chitosan 4 × 104–2 × 105 • Emulsifier Positively charged partly
• Rheology hydrophobized polymer that
modifier can gel dependent on pH and
• Preservative presence of multivalent nega-
tive ions.
1M Molecular Mass, Data from Dziezak (1991), Goldberg and Williams (1991), Le Cerf et al. (1990),
Manners (1989), Saha and Bhattacharya (2010), Stephen et al. (2006), Verbeken et al. (2003), Walstra
(2003), Williams and Phillips (2003, 2009)
Table 5.3  Application areas, E/INS numbers and main functions of various commercial natural food polymer additives and ingredients
122

Starches Carboxymethyl- Methylcellulose/ Pectin Gum Gum Karaya Locust Tara Guar Konjac Agar Carr­ Alginates Xanthan Gellan Gelatin
cellulose Hydroxypropyl- arabic Tragacanth gum bean gum Gum mannan ageenan Gum Gum
methylcellulose gum
E-number /INS E14XX E466 E461 E464 E440 E414 E413 E416 E410 E417 E412 E425 E406 E407 E401 E415 E418 N/A
number
Main functions S,T S,T S,T,G S,T,G S,T S,T S,T,G S,T S,T,G S,T T,G S,G T,G,S T,G T,S G,S G
Applications
Bakery Products ● ● ○ ● ● ● ● ○ ● ● ● ● ● ● ○ ●
Beverages ○ ● ○ ● ● ● ● ○ ○ ○ ● ○ ●
Confectionary ● ● ● ○ ● ● ○ ●
Sauces, ● ○ ○ ● ○ ● ● ○ ● ● ● ○ ● ●
dressings, soups
Dairy, acidified/ ● ● ● ○ ○ ○ ● ○ ●
fermented
drinks, desserts
Dairy, sweet ● ○ ○ ● ○ ● ○ ○ ● ○ ○ ○ ●
drinks, desserts

Flavor ○ ○ ○ ○ ● ○ ○ ○ ○
emulsions
Fruit prepara- ○ ○ ● ○ ● ○ ● ○ ● ○ ○ ○
tions, jams,
marmalades
Ice cream ● ○ ● ● ● ○ ○ ○ ○
Meat and poul- ● ● ● ○ ● ● ● ● ○ ●
try processing
Vegetable, ● ● ○ ○ ○
potato
preparations

S Stabilizer, T Thickener, G Gelling agent, ○ application areas, ● most common application areas
M. Rayner et al.
5  Application of Natural Polymers in Food 123

dispersions, and gels, as well as functioning as stabilizers of emulsion oil droplets

and gas bubbles in foams, etc. (Aguilera 2005).

5.2.1 Emulsifiers and Stabilizers

Many of the foods we enjoy are formulated products based on emulsions and
foams. Emulsifiers are added in certain food products in order to establish a uni-
form dispersion or stabilize an emulsion or foam by increasing its’ kinetic stabil-
ity. Emulsifiers are used to prevent baked goods from becoming stale, to prevent
cream sauces and mayonnaise from separating, to keep flavors suspended, and
to stabilize ice cream. To make an emulsion or foam four basic ingredients are
required: a continuous phase (1) into which a dispersed phase (2) is dispersed in
the form of small droplets or bubble, by creating an interface between the two
phases. The creation of this interface requires mechanical energy (3) from an
emulsifying device and finally some sort of emulsifier (4) that assists in lowering
the interfacial tension between the two phases assisting in the emulsification pro-
cess and/or a stabilizer that preserves the newly formed interface. Emulsions may
consist of oil droplets-in-water (O/W) or water droplets-in-oil (W/O), whereas
foams are dispersions of air-in-water (A/W), but in all cases, droplets or bubbles
need to be stabilized as this extra interface is for thermodynamic reasons inher-
ently unstable. Emulsifiers typically consist of a lipophilic or hydrophobic part
with good solubility in a nonaqueous phase (such as an oil or fat) and a polar or
hydrophilic part, soluble in water. Surfactants and small molecular weight sur-
factants typically have a hydrophilic head and a lipophilic tail (Fig. 5.1d—bottom
left). In the case of natural polymer-based emulsifiers, such as polysaccharides and
proteins the affinity for the hydrophobic phase is achieved by either modification
by lipophilic side groups (as is the case with modified starch, Fig. 5.1e—bottom
center) or by the degree of hydrophobicity of the amino acid residues as in pro-
teins (Fig. 5.1—top row).
Proteins are typically relatively small molecules (10–50 kDa) that rapidly
adsorb to the surfaces of emulsion droplets and form thin electrically charged
interfacial layers (Bouyer et al. 2012). These charges create electrostatic repul-
sion between emulsion droplets and can be an important stabilizing force for food
emulsions. Both proteins and polysaccharides can be charged, depending on the
pH, and thus, when adsorbed at the droplet interface gives rise to electrostatic
repulsion. Emulsions stabilized by electrostatic repulsions are salt sensitive and in
many cases sensitive to changes in pH. Proteins may adopt various interfacial con-
formations depending on their molecular structures and interactions (Singh 2011).
Flexible proteins, such as caseins, readily undergo conformational changes, so that
the hydrophilic groups protrude into water and the hydrophobic groups protrude
into oil adsorbing as loop-train and tail train configurations (Fig. 5.1a). Rigid glob-
ular proteins, such as β-lactoglobulin in whey (as well as some of types of egg,
soy, or pea proteins), may partially unfold exposing interior hydrophobic regions
124 M. Rayner et al.

(a) (b) (c)

(d) (e) (f)

Fig. 5.1  Schematic illustration of various types of emulsifiers and stabilizers, note scales differ

during adsorption, forming cohesive viscoelastic layers around the oil droplets
(Fig.  5.1b) (Ozturk and McClements 2016). Proteins with a large hydrophobic
domain such as oleosin (extracted from oil seeds), having 72 residues in a pre-
dominately α-helical structure (Maurer et al. 2013; Nikiforidis et al. 2013; Roberts
et al. 2008), have been reported to irreversibly bind to the oil–water interface in a
similar manner to apolipoproteins (Nikiforidis et al. 2013). Furthermore, the com-
bination of oleosins’ compact central hydrophobic pin (Fig. 5.1c) and its relatively
small overall size of (15–26 kDa) explains its good emulsifying properties, and
thus is an interesting plant-based alternative to protein emulsifiers isolated from
dairy and eggs, which has been receiving a lot of research interest (Rayner 2015).
In terms of market volumes, most natural polymer-based emulsifiers are proteins,
the ones that are sold on the largest commercial scale being dairy proteins (whey
and caseinate), various egg proteins, and soya proteins—however, other nonani-
mal-based protein emulsifiers that are gaining attention are zein and oleosin (see
Table 5.4).
Polysaccharides are generally relatively large molecules (100–1000 kDa) that
adsorb relatively slowly to droplet surfaces and form thick hydrophilic interfacial
layers (Bouyer et al. 2012). In many cases, they have been hydrophobically modi-
fied, for example, through esterification with octenyl succinic anhydride (OSA) by
incorporating hydrophobic alkenyl groups from OSA into the hydrophilic starch
molecule (Simsek et al. 2015). The large size of polysaccharide molecules means
5  Application of Natural Polymers in Food 125

Table 5.4  Common commercial protein based emulsifiers and examples of their specific key
proteins
Emulsifier Key proteins Molecular weight
(kDa)
Whey proteina β-lactoglobulin 18.6
α-lactoalbumin 14.2
Bovine serum albumin 66
Caseinsb α1-Casein 23
α2-Casein 25
β-Casein 24
κ-Casein 19
Egg whitec Ovalbumin 45
Ovotransferrin 77.7
Ovomucoid 28
Lysozyme 14.3
Egg yolkc Phosvitin 160–190
Low-density lipoproteins 16–35
Cobalamin-binding proteins 39
Riboflavin-binding; proteins 37
Biotin binding proteins 72
α,β Lipovitellins 400
Soya proteind α-Conglycinin 18–33
β-Conglycinin 104
σ-Conglycinin 141–171
Glycinin 317–360
Canola protein (rapeseed)e Oleosin 15–26
Zein protein from corn α-zein 21–25
aKinsellaand Whitehead (1989)
bSwaisgood (1993)
cAwade (1996)
dClarke and Wiseman (2000)
e Wijesundera (2014)

that they also tend to have higher surface loads than proteins, so more emulsifier
is required to cover the droplet surfaces to achieve the same level of stabiliza-
tion (Ozturk and McClements 2016). Due to their size, they can also give rise to
both depletion attraction (leading to flocculation/aggregation) and steric repulsion
(helping with droplet stabilization) depending if they are adsorbed at the interface
or dispersed in the continuous phase. Depletion attraction is due to the fact that
macromolecules (proteins, polymers, and colloidal particles) having no affinity
for the interface, will be excluded in the space between two approaching emulsion
drops, this will lead to an osmotic pressure gradient which then favors aggrega-
tion (Wahlgren et al. 2015). Depletion attraction is typically observed in emulsions
containing dissolved neutral polysaccharides. Thus, addition of polysaccharides
to alter rheology or form complex with emulsifying agents may cause depletion
126 M. Rayner et al.

aggregation (Magnusson and Nilsson 2011). On the other hand, steric repulsion
is induced by macromolecules adsorbed at the interface; this is mainly due to
excluded volume effect as adsorbed molecules come close together (Israelachvili
1985). Steric repulsion thus requires affinity of the macromolecule to the interface
but also high solubility of the macromolecule in the continuous phase. The latter
allows parts of the adsorbed macromolecule to protrude into the continuous phase,
giving rise to steric hindrance between approaching droplets. These systems are
less sensitive to salt and pH than electrostatically stabilized emulsions. For a more
detailed treatment of the emulsifying and emulsion stabilizing capacity of various
natural polymers the interested reader is directed to the comprehensive reviews
(and reference therein) on the topics of proteins as emulsifiers (Dickinson 2009,
2014; Lam and Nickerson 2013) and polysaccharides as emulsifiers (Dickinson
2009, 2014; George 2006; Kokubun et al. 2015).
In some cases, natural polymers are not used in the molecular form to stabilize
emulsions, but rather as colloidal particles in the size range of tens of nanometers
to tens of micrometers, as so-called Pickering emulsions. These particles are not
amphiphilic but rather possess a dual wettability for both phases (Fig. 5.1f, bot-
tom-right). Although adsorbed particles do not decrease the interfacial tension, and
strictly speaking are stabilizers rather than emulsifiers, they do accumulate at the
oil–water interface in an analogous way to molecular emulsifiers. However, the
key difference is that particles once located at the oil–water interface are essen-
tially irreversibility adsorbed due to their large size and exceptionally high free
energy of detachment (Rayner et al. 2014). They stabilize by a kind of steric hin-
der or volume exclusion due to their large size physically separating droplets.
Many of the recent works on particle stabilized emulsion have used natural poly-
mers to generate Pickering type particles, including starch, cellulose, chitin, soy,
and zein proteins, as well as soft microgel particles based on whey, gelatin, pectin,
or starch (Berton-Carabin and Schroën 2015; Rayner 2015; Rayner et al. 2014;
Shewan and Stokes 2013).
Stabilizers, are used to maintain a uniform dispersion of two or more compo-
nents. Although, they are not classified as emulsifiers, nor particularly surface
active, they assist in stabilizing food emulsions and foams. They are used in food
formulations in order to provide a firmer and more stable texture profile and pre-
vent the evaporation of volatile flavor components. Stabilizers are used both in dry
and liquid products. They include several natural gums, such as carrageenan, xan-
than, or locust bean gum, as well as natural and modified starches (Giannou et al.
2014). Typical products in which they are commonly used include jams, dairy
products, ice cream, baked goods, infant formulas, salad dressings, and soups.
During the production, processing, storage, transportation, and use of food
formulations based on emulsions, there are a number of destabilization processes
that can occur. The main ones which can be affected by the use of emulsifiers and
stabilizers, and natural polymers in particular include: creaming/sedimentation,
coalescence, and aggregation/flocculation. These and other common destabiliza-
tion mechanisms of emulsions and foams are illustrated in Table 5.5 and discussed
briefly below.
5  Application of Natural Polymers in Food 127

Table 5.5  Main mechanisms of destabilization in food emulsions, foams and dispersions

Mechanism (types of dispersed phase) Description, driving force, and role of natural
polymers as stabilizers (if applicable)
I Growth/dissolution (solids, liquids, gases) The driving force is the difference in the
chemical potential between the substance
making up the dispersed phase and the same
substance dissolved in the continuous phase.
If the solution is unsaturated the particles or
bubbles will dissolve, and if it is super satu-
rated they can grow (i.e., growth of crystals).
II Ostwald ripening (liquids, gases) Larger droplets of dispersed phase grow at
the expense of smaller ones when there is
sufficient solubility of the dispersed phase
in the continuous phase. The driving force
is the difference in the chemical potential of
the material between droplets of differing
surface curvature. This is partially reduced
by decreasing interfacial tension.
III Aggregation/flocculation (solids, liquids) Droplets of disperse phase stick together
either reversibility as flocculation or irrevers-
ibility as aggregation. Main cause is often
van der Walls attraction or depletion interac-
tion where the driving force is the increase
in mixing entropy of polymers molecules
present in the solution. Polymers can both
prevent and cause this type of instability
depending on conditions.
IV (a) Sedimentation (solids, liquids) Driving force is the difference in density
between the dispersed phase and continuous
phase causing either sedimentation (i.e., a
denser disperse phase is sinking) or creaming
(i.e., a less-dense dispersed phase is buoyant).
(b) Creaming (solids, liquids, gases) This process can be greatly slowed or arrested
by thickening and/or gelling agents by the
process of increasing the continuous phase
viscosity, or generating a gel with a yield value
that needs to be overcome before movement
of dispersed phase droplets can occur. Smaller
droplets also settle/cream much slower, thus
effective emulsifiers also help prevent this.
V (a) Coalescence (liquids and gases) Caused by the rupture of the interfacial
film between two droplets or foam bubbles.
Driving force is the reduction of free energy
of the system as the total interfacial area
decreases as bubbles/droplets merge. Close
contact between droplets is a prerequisite and
(b) Phase separation/collapse thus (III or IV) is often a precursor. As coa-
lescence progresses a total phase separation
or collapse can occur. Stabilizing polymers
can stabilize the interfacial film thus prevent-
ing coalescence. This together with lowering
the interfacial tension is the main function of
emulsifiers and emulsions stabilizers.
(continued)
128 M. Rayner et al.

Table 5.5  (continued)
Mechanism (types of dispersed phase) Description, driving force, and role of natural
polymers as stabilizers (if applicable)
VI Partial coalescence (liquids with particles/ A complicated phenomenon that can occur
crystals) when lipid crystals form in a cooled emulsion
and penetrate neighboring droplets creating
an oil-bridge between them. Upon re-heating
coalescence and phase separation can occur.
Natural polymers can help improve freeze
thaw stability by creating a strong interfacial
film preventing crystal penetration, as well as
ice crystal propagation.
Inset figures redrawn from Walstra (2003). Dotted arrows indicate possible irreversibility

Creaming/sedimentation occurs in emulsions and dispersions due to the den-

sity difference between the two phases. The rate of creaming and sedimentation
can be reduced by decreasing the size of the dispersed phase droplet (or bubble),
increasing the viscosity of the continuous phase, or by decreasing the difference
in densities between the two phases. The rate at which a single spherical droplet,
bubble, or particle will cream (or settle) in a Newtonian fluid can be predicted by
the Stokes velocity, υStokes:

2gR2 (ρ2 − ρ1 )
υStokes = −
9η1

where g is acceleration due to gravity, R is the radius of the creaming/settling

entity, ρ1 and ρ2 are the densities of the continuous phase and the dispersed phase
respectively, and η1 is the continuous phase viscosity. Stokes equation is somewhat
idealized, as in reality droplets are not all the same size and will be interacting dur-
ing creaming or settling. Natural polymers (such as modified starches and gums)
are often added to food emulsions to modify their flow behavior, which often
results in a non-Newtonian rheology of continuous phase. Many of these natural
polymer solutions exhibit pronounced shear thinning behavior, having a high vis-
cosity at low shear rates that decreases dramatically over a certain range as the
shear rate is increased (see Sect. 5.2). This property is important because it means
that the droplets are prevented from creaming during storage, yet the food emul-
sion still flows easily when poured from a container as the shear rate increases.
Since creaming usually occurs when an emulsion is at rest, it is therefore important
to know the apparent viscosity that a droplet experiences as it moves through the
continuous phase under these conditions. The shear stress, τgravity acting on a drop-
let undergoing gravitational separation is: τgravity = 2(ρ2 − ρ1 )gR. Which is typi-
cally between 10−4 and 10−2 Pa for food emulsions based on typical droplet sizes
and phase densities (McClements 2005, 2007; Walstra 2003). Solutions of natural
polymers used as thickening agents have extremely high apparent shear viscosities
at low shear stresses, and hence, the creaming of droplets will be greatly reduced.
Some polymer solutions have a yield stress, τyield, below which the solution acts
5  Application of Natural Polymers in Food 129

like an elastic solid, and above which it acts like a viscous fluid (Walstra 2003).
In these systems, droplet creaming is effectively arrested when the yield stress of
the continuous phase is larger than the stress exerted by a droplet due to gravity,
i.e., τyield > |2(ρ2 − ρ1 )gR|. Typically, a yield value of about 10 mPa is required
to prevent emulsion droplets of a few micrometers from creaming, which is often
exceeded in practice (Walstra 2003). The above discussion highlights the impor-
tance of carefully defining the rheological properties of the continuous phase and
understanding the action of natural polymers that may improve emulsion stabil-
ity by the action of thickening and gelling (discussed more in Sects. 5.2 and 5.2.3
respectively) (Dickinson 2009; Dickinson and Walstra 1993).
Coalescence occurs to minimize the oil–water interface and hence the free
energy. It leads to larger dispersed phase droplets and can eventually lead to com-
plete phase separation of the emulsion. It can mainly be controlled by the adsorp-
tion of emulsifiers, such as proteins and modified starches, or stabilizing particles
to the oil–water interface. They prevent coalescence either through a steric barrier
or electrostatic repulsion which hinders drop–drop contact and thus the process of
coalescence. Increased viscosity of the continuous phase can also decrease the rate
of coalescence as creaming is often as precursor to coalescence.
Flocculation is the aggregation of droplets. Flocculated systems may have
desired properties for the formulation such as beneficial rheology, but exten-
sive flocculation leads to increasing creaming and thus may lead to coalescence.
Changes in the degree of flocculation can also affect the rheology of the emulsions
changing properties such as mouth feel (Wahlgren et al. 2015).
The colloidal stability of the emulsion will be governed by the repulsive/attrac-
tive forces between individual droplets of dispersed phase (as described above), as
well as the energy and rate of droplet collisions allowing for flocs or aggregates
to arise. The choice of emulsifier could influence all of these, and a proper choice
of viscosity modifier (such as thickeners and gelling agents discussed below) will
influence all kinetic factors such as collision of droplets and diffusion of dissolved
molecules.
Freeze/thaw stability is an important industrial property, as many foods are stored
and transported at low temperature. When a food emulsion is being cooled and
eventually frozen, a variety of physicochemical processes may occur including fat
crystallization, ice formation, interfacial phase transitions, and other conformational
changes (Walstra 2003). When O/W emulsions are cooled to temperatures where
only the oil phase becomes partially crystallized, a phenomenon known as partial
coalescence is likely to happen due to penetration of oil crystals from one droplet
into the liquid region of another partially crystalline oil droplet. Upon increasing
the temperature again, it is often seen that emulsions subjected to partial coales-
cence undergo phase separation or that the emulsion becomes grainy and watery.
On the other hand, when O/W emulsions are cooled to the temperature where the
water phase also crystallizes, a number of additional physicochemical processes are
likely to happen including: formation of ice crystals which force oil droplets to close
proximity, the disruption of emulsifiers at droplet surfaces, freeze concentration of
solutes in the unfrozen aqueous phase which may alter the electrostatic repulsion
130 M. Rayner et al.

between the droplets, and the possible penetration of ice crystals into the interfacial
membranes making droplets prone to destabilization upon thawing, and the possibil-
ity for emulsifiers may lose their functionality (Thanasukarn et al. 2004). Although
in general, the main factors that affect the freeze thaw stability of emulsions are
related to the physical properties of the oil phase and the oil content (Magnusson
et al. 2011), use of some additives can increase the freeze thaw stability of emul-
sions. For example, the freeze thaw stability of emulsions can be increased by the
addition of cryoprotectants, such as polyols (sucrose, glucose, fructose, trehalose,
maltose), antifreeze proteins, gelatin, and some carbohydrates (Degner et al. 2014).
These alter the crystallization of water and the morphology of the ice crystals but
some of them can also function by increasing viscosity and thus decreasing the num-
ber of oil droplet collisions leading to coalescence. The addition of polysaccharides
has also been seen to improve freeze–thaw stability. This could be due to several
factors, but increased viscosity of the nonfrozen phase and the capability of some
polysaccharides to form protective layers around the dispersed phase hindering coa-
lescence play a major role (Degner et al. 2014). The emulsifier is critical when it
comes to destabilization due to increased concentration but can also be important
for lipid crystallization induced freeze thaw instabilities. Emulsifiers that are able to
stabilize droplets having a thick interfacial layer, at high oil concentrations, have also
been reported to improve the freeze–thaw stability of emulsions. Examples include
Pickering emulsions using quinoa starch granules or egg yolk granules as stabilizing
particles (Marefati et al. 2013; Rayner et al. 2014), proteins, such as caseins, pro-
tein–polysaccharide complexes, and hydrophobic starches (Degner et al. 2014).
Process stability during drying of emulsions, like freeze–thaw stability, the
ability of an emulsion formulation to be dried has a great deal of practical appli-
cation in foods. Dehydration of emulsion systems have been used to increase
shelf life, improve their use, and facilitate transportation (Adelmann et al. 2012;
Bhandari et al. 1993; McClements 2004). However, dehydration may alter the
interfacial properties and lead to disruption and collapse of emulsions during dry-
ing (Cerdeira et al. 2005; Fäldt and Bergenståhl 1995; Rosenberg et al. 1990).
There are several approaches to maintain the stability of emulsions during drying
and subsequent storage. A common way is to add a solid hydrophilic carrier to
the aqueous phase in amounts ranging between 30 and 80 % of the total weight
of the final powder (Gu et al. 2004; Jayasundera et al. 2009). Examples of such
carrier compounds include sugars, such as lactose, glucose, as well as polysac-
charides such as maltodextrin, and cellulose (Adelmann et al. 2012; Mezzenga
and Ulrich 2010). As an alternative and to avoid carrier compounds, multiple, or
layer-by-layer (LBL) deposition of polyelectrolytes that crosslink on the droplet
surface, crosslinking of protein-stabilized interfaces, and protein–polysaccharide
conjugates have also been applied (Kellerby et al. 2006; Moreau et al. 2003; Mun
et al. 2008). Recent work in the area of particle stabilized emulsions has also elim-
inate the need for additional hydrophilic carriers, making it possible to produce
emulsion powders with high oil content (up to 80 %) based on stabilizing oil drop-
lets using starch granules (Marefati et al. 2013, 2015) or cellulose nanocrystals
(Adelmann et al. 2012; Aveyard et al. 2003; Tasset et al. 2014).
5  Application of Natural Polymers in Food 131

Fig. 5.2  Effect of polymer
concentration on apparent
viscosity of various polymer
types

5.2.2 Thickeners

Natural polymers are widely used to thicken food systems, and unlike emulsifi-
ers and stabilizers, which are used in food formulations to produce and stabilize
emulsions droplets and foams, thickeners are added to increase the viscosity of the
food without necessarily modifying other product properties. Thickeners increase
the consistency to prevent multicomponent products from separating (for example,
reducing the rate of creaming as described in Sect. 5.1). Examples of natural poly-
mers commonly used as thickeners are presented in Table 5.2. The resulting vis-
cosity of natural polymer solutions is highly dependent on the polymers’ type and
concentration. Figure 5.2 illustrates the effect of polymer concentration on appar-
ent viscosity for three polymers, caseinate, pectin, and xanthan. Both the concen-
tration and relative polymer size play a major role. Pectin and xanthan are 2–5
and 10–50 times larger than caseinate, respectively (Walstra 2003). Size, degree
of polymerization, and branching also contribute to thickening characteristics. The
process of thickening involves the nonspecific entanglement of conformationally
disordered polymer chains.
The viscosity of polymer solutions and dispersions in general, shows a marked
increase at a critical polymer concentration, commonly referred to as C ∗ (Williams
and Phillips 2003). This concentration indicates the transition from the “dilute-
region” to the “semi-dilute” overlap region (see Fig. 5.3). In the dilute-region at
concentrations well below C ∗ polymer molecules are free to move independently
in solution without touching. As concentration approaches C ∗ molecules begin to
be crowded which gives rise to overlap and entanglements as segments or poly-
mer chains and loops begin to interpenetrate. In Fig. 5.3 the zero shear viscosity
is plotted as a function of polymer concentration (log–log scale). The line has a
132 M. Rayner et al.

Fig. 5.3  Effect of polymer
concentration on viscosity
and the concept of critical
overlap concentration

linear slope that changes typically from a value within the range of 1.2–1.4 for
concentrations below C ∗ to a value of approximately 3.3 above the C ∗. However,
glactomannas (i.e., guar and locust bean gum) have a somewhat higher slope of
4.4 above the C ∗, which is thought to arise due to specific attractive interactions
between side groups on their polymer chains (Walstra 2003). Table 5.6 shows
some examples of C ∗ and slope of the lines in the non-dilute region for common
polymer thickeners.
It is important to note that the relationships in Fig. 5.3 and Table 5.6 only
applies for extremely low shear rates, as the viscosity of polymer dispersions
approaching or above C ∗ have a significant shear rate dependence. At concentra-
tions well below C ∗ polymer dispersions exhibit Newtonian behavior, i.e., the

Table 5.6  The critical Polymer C* g/100 mL Slope

concentration C* for polymer
Dextran (linear) 2.5 3.3
chain overlap and slope of the
relation: log(η)0 versus C for Guar gum 0.25 4.4
C > C ∗. Data from Walstra Na-alginate 0.2 3.3
(2003) Lambda-carrageenan 0.4 3.3
Locust bean gum 0.2 4.4
Pectin 0.3 3.3
Xanthan 0.1 3.9
5  Application of Natural Polymers in Food 133

Fig. 5.4  Effect of shear rate

on the apparent viscosity of
xanthan solutions at 0.05 and
0.25 ww% (data redrawn
from Walstra (2003) based on
various sources)

viscosity is independent of shear rate, however, above C ∗ non-Newtonian behav-

ior is generally observed for polymer dispersions (Williams and Phillips 2003,
2009) and is strongly shear thinning over a given shear range (Walstra 2003). This
phenomenon is illustrated in Fig. 5.4 showing the change in apparent viscosity of
xanthan dispersions, at polymer concentrations both below (0.05 %) and above
(0.25 %), C ∗ (being approximately 0.1 %), as a function of shear rate. Here, the
apparent viscosity decreases by over three orders of magnitude over the range of
shear rates applied for concentrations above C ∗.
The curves in Fig. 5.4 also display three distinct regions as the shear rate
increases: (i) an initial high viscosity low shear Newtonian plateau, (ii) a shear
thinning region, and (iii) a high shear low viscosity plateau (if extended to even
higher shear rates). The molecular-microstructural explanation of this phenome-
non is as follows: in region (i) at very low shear rates, as many new entanglements
between polymer molecules form as are disentangled per unit time, the viscos-
ity is Newtonian and remains high. In this case, due to the polymer concentra-
tion exceeding the critical overlap concentration, polymers chains readily develop
entanglements. The higher the polymer concentration, the greater the number of
such entanglements per unit volume, and disentangling them requires a relatively
larger amount of energy, thus, the much higher apparent viscosity low shear rates
(region (i) in Fig. 5.4). When applying a shear rate to the polymer solutions/dis-
persions, the shearing stress provides the energy causing disentangling. However,
Brownian motion of the polymer chains allows new entanglements to form. The
time available for the formation of new entanglements during shearing is roughly
on the order of the reciprocal of the shear rate. The apparent viscosity under a
given shear rate is thus a balance between the number or entanglements possible
based on the concentration and the relative time of entanglement and disentangle-
ment processes. As the shear increases beyond the point that the Brownian-driven
re-entanglements cannot keep up with the shear-driven disentanglements, the
134 M. Rayner et al.

apparent viscosity drops (region (ii) in Fig. 5.4). If the polymer molecules become
fully disentangled the viscosity will be significantly lower and no longer a func-
tion of shear rate, as seen in region (iii) in Fig. 5.4. At very high shear rates, the
time available for entanglements relative to the rate they are being pulled apart
by the shear is short, thus, the polymer molecules are basically fully disentangled,
yielding a relatively low and constant viscosity. Here, disentanglement dominates
and viscosity drops to a minimum plateau at infinite shear rate (Williams and
Phillips 2009). The relationship between the apparent viscosity at a given shear
rate depends on the polymer type, size morphology, and solvent quality (Walstra
2003). Linear stiff molecules have larger hydrodynamic size than highly branched
flexible polymers of the same molecular mass, and hence higher viscosity, assum-
ing that other conditions are constant. Viscosity shear rate dependency increases
with increasing molecular mass, and the shear rate at which shear thinning occurs
[i.e., onset of region (ii)] shifts to lower values (Williams and Phillips 2009). For
more details on the rheological properties of specific polymers the interested
reader is recommended the Handbook of Food Hydrocolloids (Williams and
Phillips 2009), as well as comprehensive reviewers on thickeners and references
within (Chronakis and Kasapis 1995; Gibinski et al. 2006; Marcotte et al. 2001;
Saha and Bhattacharya 2010; Sheldrake 2003; Sopade et al. 2008; Tolstoguzov
2008; VâniaReginaNicoletti 2012).

5.2.3 Gelling Agents

Although all hydrocolloids thicken and increase the viscosity of aqueous disper-
sions, a few natural polymers have an additional key property of being able to
form gels. Example of common natural polymers used as gelling agents and some
of their properties are presented in Table 5.2. Gel formation arises from the associ-
ation or crosslinking of polymer chains, thereby creating a three-dimensional net-
work trapping water within it to form a semi-rigid structure being resistant to flow.
Natural polymer-based gels are generally viscoelastic exhibiting characteristics of
both liquids and solids depending on the applied deformation stress. Viscoelastic
behavior is often characterized using a rheometer that measures the mechanical
reaction of a material undergoing deformation at controlled rate (frequency) or
controlled stresses. As the name implies, viscoelastic materials have both viscous
and elastic properties being characterized by the magnitude and frequency depend-
ence of the storage, G′ and loss modulus, G′′. In dilute systems, where the polymer
concentration is <C ∗ and molecule entanglements do not occur, most polymers
have a loss modulus (i.e., viscous dissipation of the applied stress at a given rate)
greater that the storage modulus (the ability of an elastic body to store energy).
As the concentration increases, intramolecular entanglements occur and if these
are more enduring then a three-dimensional network structure can form creating a
gel. The critical minimum concentration at which gelling occurs is often denoted
C0, and is specific for each natural polymer, and can vary greatly. Agarose, for
5  Application of Natural Polymers in Food 135

Fig.  5.5  Qualitative comparison of gel textures produced by different natural polymers.

Redrawn based on Williams and Phillips (2009)

example, gels with as little as 0.2 % while for acid thinned starch a concentra-
tion of up to 15 % is required before gels are formed. In general, for most natural
polymers C0 is in the range of up to 1 % (Williams and Phillips 2009) (note C0
is not the same as C ∗ presented above). Once formed, the specific textural prop-
erties (such as being elastic or brittle, chewy, or creamy, etc.) and other sensory
properties (such as opacity, mouth feel, and taste) generated depend on the type
and concentration of the gel forming polymers added in the formulation (Saha and
Bhattacharya 2010).
A qualitative comparison of the textures of gels produced by various types of
natural polymers commonly used in foods is illustrated in Fig. 5.5. Natural poly-
mer gels also vary considerable in strength and elasticity owing to differences in
the number and nature of the physical bond that join the polymers together, as well
as the degree of aggregation between chains (Williams and Phillips 2003).
Proteins and polysaccharides are able to form gels by physical association of
their polymer chains by a number of mechanisms: hydrogen bonding, hydropho-
bic association, and cation-mediated crosslinking. In some cases, natural polymer
gels undergo covalent crosslinking, however, this is more uncommon. These zones
of interaction that give rise to gel network formation are called gel junctions and
are illustrated in Fig. 5.6. In most polymer gels, the junctions contain a substan-
tial proportion of the polymer material, up to 30 % (Walstra 2003). Within food
there are two main types of gels—polymer gels and particle gels, with polymer
gels being the most common.
Polymer gels are made up of long polymer molecules that are crosslinked at
some places. These crosslinks are rarely chemical bonds, with the exception of
sulfide bridges (–S–S–) between protein molecules in, for example, whey gels
(Fig.  5.6a), but rather junction zones comprising of a large number of relatively
weak physical bonds. These bonds are often microcrystallites, i.e., straightened
136 M. Rayner et al.

Fig. 5.6  Types and scales of gel structures, showing various types of gel junctions. Redrawn
from Walstra (2003)

polymer sections (Fig. 5.6b), or stacks of helices (Fig. 5.6d and e). Polymer gels
with microcrystallites: here the gel structure is made up of junctions that are cre-
ated by a large number of weak physical bonds in regions of micro-crystallinity,
rather than covalent chemical bonds. These weak physical bonds arise from Van
der Waals attraction, hydrophobic interaction, and hydrogen bonding. In the case
of charged polymers, ionic bonds can also be involved. Most gels with microcrys-
tallite junctions are thermoreversible—they melt upon heating and (re-) form upon
cooling. The other types of junctions that can be formed are “egg-box” junctions
(Fig. 5.6f) in the presence of calcium ions, as in the case of anionic polymers like
alginates. Gels based on “egg-box” junctions do not generally melt at high tem-
perature and are considered thermoirreversible. In case of protein gels, the gelation
of proteins requires a driving force to unfold the native protein structure (often
heat), followed by an aggregation process giving a three-dimensional organized
network of aggregates or strands of molecules crosslinked by non-covalent bonds,
and in some cases by covalent bonds (Totosaus et al. 2002). Among natural poly-
mer protein ingredients, gelatin has a preponderant role in formulated foods due to
5  Application of Natural Polymers in Food 137

its unique functional properties. Gelatin produces transparent gels with the highly
desirable ability to melt in the mouth, which is unparalleled by other gelation
agents.
Particle gels are generally formed by the fractal aggregation of particles
(Fig. 5.6c), where the particles are made up of natural polymers, for example, pol-
ysaccharide microcrystals or casein micelles. Here, the gel structure is determined
by the volume fraction of the particle material, their size, and the fractal dimen-
sion of the aggregates. A typical food example of fractal particle gels is gelled
casein micelles that are driven to aggregate by the action of acidification or rennet
(Walstra 2003). In this context, the junction zone of a particle gel could be consid-
ered as the particle–particle interaction points.
Microgels are soft, colloidal particles made of highly swollen crosslinked pol-
ymers, which have recently been receiving significant research interest (Schmitt
and Ravaine 2013). They are distinct particles that are made of a gelled material,
and thus, microgels themselves can create a fractal particle gel, or even be used as
a type of soft particle in stabilizing emulsions and foams. Food grade microgels
have been generated from polysaccharides such as inulin (Sahiner et al. 2014),
crosslinked starch, by the partial gelatinization of starch granules (Dickinson
2015; Rayner et al. 2014; Sjöö et al. 2015), proteins (Destribats et al. 2014; Phan-
Xuan et al. 2014; Schmitt et al. 2014, 2010; Tan et al. 2014), and protein–pectin
mixtures (Zimmerer and Jones 2014). They are generally generated through cova-
lent crosslinking of proteins through a complex process of denaturation, aggrega-
tion, electrostatic interactions, and the formation of di-sulfide bonds (Schmitt et al.
2010). In the case of whey protein microgels, this is achieved by a combination
of fast heat treatment in a plate heat exchanger, high shear, microfiltration, and
in some cases a final spray drying step is performed producing a whey protein
microgel powder that is readily re-dispersible (Destribats et al. 2014; Schmitt et al.
2010; Dissanayake et al. 2012). The resulting whey protein microgels are very
efficient in the stabilization of emulsions and foams and will likely see greater
industrial use in the near future.
The formation of all types of gels depends on a number of physicochemical
phenomena that leads to the creation of junction zones. These “gelation reactions”
can be roughly classified as either physically induced (heat, pressure) or chemi-
cally induced (acid, ionic, enzymatic) and are described briefly below.
Temperature: Heat-induced gelation is probably the most important and com-
mon method to obtain gels (Aguilera and Rademacher 2004). Gelation is a two-
step process; an unfolding or dissociation of the molecules due to that the energy
input takes place in the beginning to expose reactive sites. The second step is the
association and aggregation of unfolded molecules to form complexes of higher
molecular weight. The first step may be reversible while the second one is usually
an irreversible process (Banerjee and Bhattacharya 2011).
Pressure: High pressure offers an additional option in creating gels during pro-
cessing by modifying functional properties of molecules. In this case, high pres-
sure can be applied as a single process or in combination with others (i.e., heating
or chemically induced gelling described below). In general, high pressure favors
138 M. Rayner et al.

reactions, as it causes water to dissociate and the pH of solution becomes more

acidic (Banerjee and Bhattacharya 2011).
Ionic Strength: Monovalent and divalent cations such as sodium and cal-
cium can increase the ionic strength of polymer solutions causing the reduction
of the electrostatic repulsive forces between the molecules and gelation can occur
(Banerjee and Bhattacharya 2011). Ionic-induced gelation has been reported for
pre-denatured whey proteins, however, in industrial applications, ionic-induced
gelation is much more common in polysaccharide gels such as alginate, pectin,
and carrageenan.
pH: Changes in pH, for example, by the addition of acids or microbial fermen-
tation, changes the net charge of polymer molecules, and thus, the attractive and
repulsive forces between molecules and hydration properties. In addition, the solu-
bility of salts changes with pH which may contribute to gel formation (Banerjee
and Bhattacharya 2011). Changes in pH can also cause aggregation of particles in
fractal particle gels such as those based on casein micelle in acidified dairy prod-
ucts (Walstra 2003).
Enzymatic activity: Enzyme-induced gelation is based on the introduction of
artificial covalent crosslinks into food proteins. For example, protein crosslink-
ing reactions catalyzed by trans-glutaminase (TG), peroxidase, and polyphe-
nol oxidase (Lauber et al. 2003). Another common enzymatic action causing the
formation of particle gels is the action of rennet on casein micelles allowing for
aggregation (Walstra 2003).
Solvent quality: The nature and presence of solvent markedly influences gel
formation, for example, concentrated sugar solutions is a poor solvent for pectin,
and thus assists in the gelling of jams and jellies. Here, hydrogen bonds in the
junction zones can only be formed in concentrated sugar solution, and hence, gela-
tion takes place only with the addition of a certain amount of sugar.

5.2.4 Characterization of Natural Polymer Formulations

From a consumers’ viewpoint, apart from taste, the two most important food prod-
uct properties are physical appearance (phase separation, creaming, sedimenta-
tion, graininess, etc.) and texture (mouth feel, viscosity, etc.), and these are closely
related to the stability of emulsion droplets, as well as the rheology of the resulting
dispersion or gel. For this reason, the microstructure and particle size distribution
of emulsions and/or the texture and rheology of the system is often studied in the
development and evaluation of new natural polymer based formulations.
On a microstructural level, emulsion droplet size distribution is perhaps the
most central quantifying measure in emulsion science, as emulsion characteristics
and performance are to a large extent determined by their droplet sizes (Wahlgren
et al. 2015). There are numerous methods to assess particle size distributions in
emulsions, including direct droplet measurement by microscopy (light, confocal,
electron, etc.), automated particle counters (i.e., Coulter counter), light scattering
5  Application of Natural Polymers in Food 139

(i.e., Malvern Mastersizer), dynamic light scattering, diffusional wave spectros-

copy, NMR, and sedimentation or centrifugation (Walstra 2005). These techniques
vary with respect to size ranges covered, measurement principles, degree of sam-
ple preparation, and dilution, as well as physical limitations. The interested reader
is directed to comprehensive and critical reviews and references therein on emul-
sion characterization techniques for more details (Dalgleish 2003; Dickinson
2013; McClements 2005, 2007; Sherman 1995; Walstra 2005).
As pointed out previous, the action of natural polymers dispersions and gels
in modifying product rheology is important to developing texture and mouth
feel as well as emulsion stability (with respect to creaming and coalescence) (Le
Révérend et al. 2010; Tadros 2004). Texture can be evaluated using techniques
such as by oscillatory rheometers and texture analyzers. While texture analyzers
can give quick information for comparison of systems they are empirical, while
the data obtained by oscillating rheology gives more fundamental information.
The modern development of controlled stress rheometers has allowed for char-
acterization to be carried out at small strains and stresses, thus measurements do
not destroy the structure of the samples. In this type of measurement, the sample
is subjected to a sinusoidal shear deformation and the resultant stress response is
measured. The frequency and the strain/stress on the sample can normally be var-
ied and the response is divided into a viscous component G″ (loss module) and
an elastic component G′ (storage module). Such measurements can give informa-
tion of the viscoelastic character of the material over a wide range of stress and
strain rates. Typically in strain tests, the strain is increased until the structure of
the material is broken and the gel starts to flow shown as a rapid decease of elas-
tic modulus G′. As mentioned in Sect. 5.1, even a weak gel can arrest the cream-
ing of emulsions and thus, gelling polymers will only have to withstand the
stress asserted by the droplet. Therefore any measurement to predict if the sys-
tem is resistance to creaming will have to be evaluated at low stress, which can be
obtained by constant stress or creep measurements. Oscillating measurements can
also be used to follow the build-up of a gel during heating or cooling.
In addition to texture analyzers and controlled stress oscillatory rheometers
there are several additional methods that evaluate texture properties of natural
polymer dispersions and gels. For example, the RVA is a rotational viscometer
which records the viscosity of a sample continuously during a preset controlled
temperature profile. From the samples’ viscosity profile, several parameters can be
obtained, see Fig. 5.7 (Crosbie and Ross 2007). RVA type measurement have been
used extensively in characterizing native starches with respect to gelatinization
and pasting properties, as well as the ratio between the constituent amylose and
amylopectin molecules. Properties of modified starches studied by the temperature
cycling action of the RVA includes: studying how crosslinking starch increases its’
stability to heat, shear, and acid, and how ethers or esters substitution improves
freeze–thaw stability. Beyond starch applications, information and properties
of different non-starch hydrocolloids have been obtained with the RVA. In most
cases the cooling curve reveals the information. This is, therefore, also applica-
ble when hydrocolloids are mixed with starch, since the pasting of the starch has
140 M. Rayner et al.

Fig. 5.7  Typical RVA heating and cooling curve, showing the main parameters

already occurred before the cooling begins. Hydrocolloids such as carrageenan,

guar gum, locust bean gum, xanthan, and konjac mannan all give specific cool-
ing profiles (curve shapes) that can be associated with specific product properties
(Young 2007). In this section only a short overview of characterization methods of
texture and rheology has been provided. For a more extensive reviews on this topic
the reader is directed to Derkach (2009), Tabilo-Munizaga and Barbosa-Cánovas
(2005), and Tadros (2004).

5.3 Additional Physiological and Biological Functions

5.3.1 Health Effects of Natural Polymers

In addition to their classical food formulation applications discussed above, some

natural polymers, mostly the soluble non-starch polysaccharides, such as pectin,
guar gum, ispaghul, beta-glucan, inulin, and gellan have additional health bene-
fits that arise from the specific structural properties they exert in the food matrix.
The effect of these polysaccharides are dependent on both the dose ingested and
whether they are bound or free to form viscous solutions (Brennan et al. 1996).
Generally, the health beneficial effects are achieved with higher levels than is
typically used in food products. For example, the typical usage level of guar gum
is <1 % in food products but to achieve health effects, the levels must be up to
3–5 % which unfortunately can be associated with a negatively slimy mouth feel
(Edwards and Garcia 2009). However, despite the additional challenges of creat-
ing pleasing and functional products, natural polymers are still providing sound
alternatives to traditional pharmacological approaches for treating and preventing
5  Application of Natural Polymers in Food 141

Fig. 5.8  Health effects of natural polymers in the GI tract

a number of diet related conditions, such as obesity, blood cholesterol levels, and
gut health (Fig. 5.8).

5.3.2 Effect of Natural Polymers in the Upper

Intestine—Prolonging Satiety
and Inducing Weight Loss

Many drugs designed to facilitate weight loss usually fail due to limited effi-
cacy, high drop-out rate in long-term treatment, concerns of side effects and
safety (Lai et al. 2015; Misra 2013). From the pharmacological area, novel appe-
tite suppressing agents, such as Rimonabant (a cannabinoid receptor blocker,
initially intended as an anti-obesity and smoking-cessation dual-purpose drug)
and Orlistat (a pancreatic lipase inhibitor reducing fat absorption) have been
developed during recent decades. Unfortunately, Rimonabant were accompa-
nied with psychiatric side effects and were withdrawn from the market. Orlistat
is the only clinically approved drug on the market today and is also accompa-
nied with side effects as steatorrhea, bloating, and fecal incontinence (Lagerros
and Rossner 2013). However, further investigation is required due to the severe
side effects and long-term safety of the pharmacological agents (Lai et al. 2015;
Misra 2013). Therefore, a considerable amount of edible extracts with botani-
cal origin are screened for their appetite suppressing properties including thyla-
koid membranes (Ostbring et al. 2014) and galactolipids (Chu et al. 2009) from
142 M. Rayner et al.

spinach, polyphenols from tea plant extract (Kobayashi et al. 2009), saponins from
Japanese horse chestnut (Kimura et al. 2006), and terpene extract from bark of
birch (Jager et al. 2009). Since the origin is food and has been consumed in many
cultures for a very long time, the extracts are considered to be safe also in the long
term.
Appetite is regulated by complex mechanisms and is controlled by the central
nervous system. Mechanical actions involved in food intake and digestion, such
as chewing, stomach distension, and peristaltic movements of the intestines play
a role in the regulation of appetite signals. Also, the food composition influences
appetite where fat, protein, and carbohydrate have different satiation actions.
Certain hydrocolloids, such as guar gum, alginates, inulin, pectin, beta-glucan,
psyllium, and ispaghula have gel forming properties that increase viscosity of the
digesta which elicit effects that modulate appetite (Blundell and Stubbs 1999).
Solid or highly viscous foods are expected to elicit stronger satiation (the
immediate response that initiates meal termination) and satiety (the long-term
absence of hunger between meals) compared to liquids. Solid and viscous food
requires increased mastication compared to liquids. Thus, the food spends longer
time in the oral cavities, which prolong metabolic feedback for satiety signals to
the appetite center in the central nervous system (Fujise et al. 1998).
Gel forming polysaccharides with high viscosity can change the characteristics
of the liquid phase of ingested food in the stomach. Gel forming polysaccharides
thereby increase gastric volume compared to high- or low viscosity meals that do
not gel (Dikeman et al. 2006). The higher gastric volume increases distension in
the stomach wall and activates gastric mechanoreceptors which (i) sends neural
signals mediating satiety to the appetite center in the brain and (ii) sends signals
that delays gastric emptying (Sturm et al. 2004). Delayed gastric emptying is a
key process in the regulation of appetite as gastric distension is also an important
signal to influence satiety, prevent overeating, and hence, weight control (Edwards
and Garcia 2009). High viscosity, gel forming polysaccharides ingested in high
concentrations increase gastric volume and enhance fullness compared to high- or
low viscosity meals that do not gel and are more homogeneously diluted in the
stomach (Dikeman et al. 2006; Hoad et al. 2004).
When the transit of nutrient from the stomach to the intestines is slowed
down, the absorption will be prolonged. Slowed absorption results in a reduc-
tion in postprandial glucose and insulin response, which also modulates appetite
responses (Jenkins et al. 1978). The ingestion of different types of insoluble and
soluble viscous hydrocolloids including pectin, inulin, beta-glucan, psyllium,
ispaghula husk, guar gum and modified cellulose, blunted postprandial glucose,
and insulin responses (Dikeman et al. 2006; Hoad et al. 2004; Maki et al. 2008).
Furthermore, ingestion of high viscous non-starch polysaccharides caused reduc-
tion in glucose and insulin concentrations after ingestion. The result was explained
by retarded gastric emptying and reduced rate of absorption (Leclere et al. 1994).
The slowed down transit of viscous digesta also allow nutrients to pass further
down the intestine to the lower part, called the ileum. When nutrients are accu-
mulated in the ileum, a feedback mechanism called the ileal brake is activated
5  Application of Natural Polymers in Food 143

which in turn promotes secretion of satiety promoting hormones and peptides,

such as peptide YY (PYY), cholecystokinin (CCK), and glucagon-like peptide 1
(GLP-1) (Maljaars et al. 2007). In response to the hormones, the gastric emptying
rate of the next meal is reduced and hence reduced postprandial levels (levels after
a meal) of nutrients in the second meal, and even a shorter time to reach satiety
from that second meal (Nilsson et al. 2008). This phenomenon is called the second
meal effect: if the digestion of the first meal is prolonged, the systemic appetite
regulation will be affected in various ways, and a lower amount of energy will be
ingested in the second meal.
Natural polymers in the GI tract also affect the absorption of nutrients by
mechanically hindering digestion. Guar gum in the intestine appears to form a
gel, hindering digestion, and absorption of available carbohydrates, and thereby,
decreases the rate of glucose absorption into the hepatic portal vein that nor-
mally follows a starchy meal. Starch fragments are thought to be caught in the
highly viscous network, making them less available for digestive enzymes (like
alpha-amylase). Thylakoid membranes from spinach has been demonstrated
both to retard uptake and passage of glucose, larger carbohydrates, and proteins
(Montelius et al. 2011). Thylakoids are thought to attach to the mucosal surface,
hindering absorption of nutrients by steric hindrance. Thylakoids have also been
demonstrated to prolong absorption of lipids by specifically inhibiting pancreatic
lipase and colipase (Ostbring et al. 2014). Alginate incorporated in bread has been
demonstrated to inhibit lipase/colipase and prolong lipid digestion and absorption.
In agreement with guar gum above, the mechanism is suggested to be enzyme
entrapment within the viscous gel, decreasing the interaction between enzymes
and substrate (Houghton et al. 2015). Since digestion is a complex process, there
is likely more than one mechanism to describe the influence of hydrocolloids in
the human gut. It has also been suggested that an increase in the viscosity of the
intestinal content reduces the mixing movements caused by intestinal contrac-
tions (Edwards et al. 1988). The reduced intestinal movements will produce lami-
nar flow, rather than turbulent flow. Laminar flow will increase the unstirred water
layer at the intestinal wall and would affect the rate at which starch fragment and
other nutrients are exposed to the epithelial surface and further absorption into the
hepatic portal vein (Li and Nie 2015).
Supplementation of guar gum and other hydrocolloids together with energy-
controlled diets has shown promising effects on weight loss and maintenance.
Obese subjects following a fixed energy diet supplemented with 40 g guar gum/
day over a week significantly decreased the energy intake compared to control
(Pasman et al. 1997). Modified guar gum (highly purified galactomannan) added
to a low-energy diet (7.5 g/day over 2 weeks) was significantly reducing weight
and prevented increases in appetite, hunger, and desire to eat compared to control
(Kovacs et al. 2001). Alginate supplemented to a beverage three times/day (totally
15 g fibers/day) together with a restricted diet significantly resulted in a greater
weight loss compared to control. The effect was attributed to lower percentage of
body fat. However, alginate supplementation showed no effect on appetite sensa-
tion such as the hunger hormone ghrelin (Jensen et al. 2012).
144 M. Rayner et al.

5.3.3 Effect of Natural Polymers on Blood Cholesterol

Levels

There is substantial evidence that hydrocolloids, which have the potential to

increase viscosity, also reduce the absorption of bile. This is probably due to
entrapment of molecules inside the polysaccharide network. Charged polysaccha-
rides as pectin, may bind bile acids thus reduce reabsorption, but most binding
sites are already occupied by other substances in the food and may therefore not
be available for binding new molecules (Edwards and Garcia 2009).
Bile salts are synthesized from cholesterol in the liver, stored in the gall bladder
and secreted into the intestine after meals to promote digestion and absorption of
fat. Synthesis of bile is an energy consuming process. To minimize the produc-
tion, and still allow the large physiological need, an efficient circulation of bile
is performed. After taking part in the lipid digestion, bile is reabsorbed by active
transport in the ileum and transported back to the liver in a circulation called the
enterohepatic circulation. When bile is trapped in a polysaccharide gel in the intes-
tine, they pass through the GI tract without being reabsorbed, and the systemic
bile pool is decreased. To maintain the physiological needs of bile, new molecules
are being synthesized from circulating blood cholesterol, thus reducing the overall
cholesterol levels in the body. Supplementation of pectin, psyllium, beta-glucans,
and guar gum has been demonstrated to reduce total cholesterol and LDL cho-
lesterol in several human studies (Brown et al. 1999; Cicero et al. 2015; Salas-
Salvado et al. 2008).

5.3.4 Effect of Natural Polymers in the Lower Intestine

Dietary fibers are defined as polysaccharides and lignin which are resistant to the
endogenous enzymes in the human digestive tract. Thus, dietary fibers are not
digested during transit through the small intestine. When dietary fibers reach the
colon, they are fermented by the colonic microflora. Examples of hydrocolloids
being substrate for colonic fermentation are pectin, beta-glucan, and non-digest-
ible oligosaccharides such as fructooligosaccharides and inulin. The fermenta-
tion produces short chained fatty acids (SCFAs), mainly acetate, propionate, and
butyrate, but also carbon dioxide, hydrogen, and methane gases. These fermen-
tation products have several benefits for the human health. The absorption of the
SCFAs promotes water absorption and helps prevent diarrhea (Crump et al. 1980).
SCFAs stimulate electrolyte absorption by the mucosa and enhance transport
through improving colonic blood flow. Production of SCFAs increases gut acidity,
which reduces putrefaction and activity of pathogenic bacteria, which lowers tox-
ins and thus reduces bad odors and bad smelling feces.
Butyrate production has received the most research attention due to its potential
anti-inflammatory effects. Butyrate is the preferred energy source for the colonic
5  Application of Natural Polymers in Food 145

microflora and is thought to be essential for colonic health (Roediger 1982). It also
stimulates the proliferation of intestinal cells (Sakata 1987) and promotes colonic
healing from surgery and after inflammation (Scheppach et al. 1992; Topcu et al.
2002). Inflammation is a major factor in many diseases such as cardiovascular dis-
eases and cancer and epidemiological studies have shown that populations with
high intake of fibers in their diet have reduced risk of colon cancer. Protection may
be through the colonic production of butyrate which inhibits the growth of tumor
cells in vitro by stimulating programmed cell death (Hague and Paraskeva 1995).
Propionate, another SCFA is used mainly in the liver where it is thought to
reduce the synthesis of lipids from acetate (Wolever et al. 1995) and possibly
cholesterol synthesis (Chen et al. 1984). Another SCFA, acetate, is thought to
increase plasma lipids, which increases the risk of thrombosis and atherosclerosis.
Different food compositions give rise to different amounts of acetate, propionate,
and butyrate and a lower proportion of acetate to propionate may be important in
promoting a healthier plasma lipid profile (Wolever et al. 1991).
Fermentation can be associated with increased gas production and may cause
discomfort if the gas is retained in the colon. Gas production will however stimu-
late stretch receptors in the colonic muscle and this will increase the transit rate
through the colon and may feed back to the stomach and cause delayed gastric
emptying which is associated to satiety (Edwards and Garcia 2009).
Some hydrocolloids such as ispaghula, gellan, and psyllium are resistant to
gut fermentation and cannot be utilized by the microbiota, but they do have other
health benefits. These carbohydrates have a much greater effect on stool output
compared to fermentable carbohydrates. Guar gum, pectin, inulin, and beta-glu-
can are likely to be completely fermented in the colon but non-fermentable car-
bohydrates retain their water holding capacity through GI transit (Edwards and
Eastwood 1995). This enables increased fecal bulking which ease laxation very
efficiently, leading to relief of constipation, one of fiber’s best-documented effects.

5.3.5 Natural Polymers Can Improve Bioavailability

of Vitamins and Other Sensitive Components

Several natural and essential nutrients, such as vitamins, carotenoids and ω-3 pol-
yunsaturated fatty acids are prone to degrade when subjected to heat, light, or oxy-
gen (Mao and Miao 2015). Furthermore, they are often poorly soluble in water
and these characteristics together limit their wider application in the food industry.
To overcome these challenges, a wide variety of colloidal delivery systems such
as structured emulsions have been designed so that the sensitive nutrients can be
dispersed into aqueous-based food and beverage products with improved physico-
chemical stability, process ability, and bioavailability (Garti and Yuli-Amar 2008;
Ozturk et al. 2015; Saberi et al. 2013; Velikov and Pelan 2008).
146 M. Rayner et al.

During transit through the GI tract, the structure of food emulsions is largely
modified before entering the intestine where most nutrient absorption is taking
place. Food emulsions are prone to microstructural changes, such as flocculation,
coalescence, and creaming during digestion and the intensity of these processes
greatly affect the delivery efficacy such as bioavailability of the nutrients (Mao
et al. 2009). Accumulated evidence has shown that conventional oil-in-water emul-
sions can only provide limited protection for nutrients during digestion, and it is
difficult to control the delivery (McClements 2010). Many efforts have therefore
been spent on creating desired structures in the water and oil phases and the inter-
face between them. Three examples of successful approaches are multilayer emul-
sions, multiple emulsions, and gelled emulsions. The delivery systems improve
emulsion stability and facilitate targeting of nutrient delivery during digestion.
Multilayer emulsions are emulsions where the droplets are surrounded by two
or more layers. The layers are attached by the layer-by-layer technique (Hou et al.
2010). The first layer to be deposited onto the droplet surface is often a charged
emulsifier (e.g. protein or lecithin). The second layer is an oppositely charged
emulsifier (e.g. protein or SDS) or a polymer (e.g., polysaccharide). The sec-
ond layer is thereby electrostatically attracted to the previously adsorbed layer,
which increase the stability. Multilayer emulsions have been reported to have bet-
ter stability against heating, freeze thawing, high ionic strength and pH change
compared to conventional emulsions (Guzey and McClements 2006). They can
therefore be used to protect and control release of sensitive nutrients in a con-
trolled manner. Hou et al. (2010) used multilayer emulsions to protect beta-car-
otene from degradation during storage. The layers surrounding the emulsion
droplets were soybean polysaccharide and chitosan. By adding chitosan as a sec-
ond layer, the loss of beta-carotene were significantly reduced during storage in
different temperatures, compared to emulsions with only soybean polysaccharide
as surrounding monolayer. Guzey et al. reported that the lipid oxidation of fish oil
could be reduced by more than 50 % using a double layer (SDS-chitosan) or triple
layer (SDS-chitosan-pectin) emulsion compared to a single layer emulsion (SDS)
(Guzey and McClements 2006).
Multiple emulsions are emulsions dispersed in the same phase as the emul-
sion droplets and are sometimes referred to as double emulsions. They contain
two water and one oil domain (w/o/w emulsions) or two oil and one water domain
(o/w/o emulsions). This structure allows prolonged delivery and higher encapsula-
tion efficacy. Another feature with this delivery system is that it makes it possible
to control the release of both lipophilic and hydrophilic substances in the same
system (Mao and Miao 2015). O’Reagan et al. found that encapsulation of Vitamin
B12 in double emulsions improved the chemical stability during storage (O’Regan
and Mulvihill 2010). Multiple emulsions have been successfully used for encap-
sulation of probiotics. The viability of lactic acid bacteria decreased rapidly when
directly dispersed in gastric juice, and less than 1 % was viable after 0.67 h of
incubation. When lactic acid bacteria were encapsulated in the inner phase of a
w/o/w emulsions, 49 % of the bacteria were alive after 2 h incubation. The viabil-
ity was dependent by the inner phase ratio and the diameter of the oil droplets
5  Application of Natural Polymers in Food 147

where larger droplets resulted in higher viability (Shima et al. 2006). W/o/w emul-
sions can be used not only to improve bioavailability of sensitive ingredients, but
also to substitute milk fat in low-fat dairy products. When the oil content in the oil
phase are partly displaced by water in the inner phase, the caloric content can be
reduced while at the same time keeping the desired viscoelastic properties such as
creaminess (Lobato-Calleros et al. 2006).
In gelled emulsions, oil droplets are trapped within gel particles. The parti-
cles decrease the mass transfer and diffusion rate of the nutrients incorporated in
the oil droplets. The gel particle can be broken down under certain environment
conditions, such as salt concentration and temperature, which allows controlled
release of the incorporated nutrients (Mao et al. 2009). Gelled emulsions are used
for controlled release of lipid soluble nutrients, such as incorporation of ω-3 fatty
acids, fish oil, flavor oil, etc. (Kim et al. 2006; Lamprecht et al. 2001; Weinbreck
et al. 2004). Hydrocolloids, such as alginate, pectin, gelatine, and starch (Malone
and Appelqvist 2003; Marefati 2015; Marefati et al. 2015) are used to create the
gel surrounding the oil droplets in gelled emulsions. The nutrients incorporated
in the gel are by this arrangement protected from exposure to oxygen, light, and
enzymes, and they usually have improved chemical stability (Kim et al. 2006).
Structuring emulsions in different ways is a promising approach to control
nutrient delivery through digestion and at the same time increase the chemi-
cal stability and bioavailability. The research field is still young and most studies
are performed in vitro. Digestion in vivo is a complex process with large individ-
ual differences, such as health state, volume of digestive juice, varying enzyme
release, and different microflora composition in the GI tract. Digestive models
must be developed to closer mimic the in vivo digestion so that the performance
of structured emulsions can be better characterized and the valuable nutrients be
protected and released at the optimal location.

5.3.6 Antioxidative and Antimicrobial Properties of Natural

Polymers

In addition to biological functionality within the human GI tract, some natural

polymers also have additional biological function that can be adapted into useful
properties in food formulations, such as antioxidative and antimicrobial functions.
One such example of a biological function being transferred into food for-
mulations is the antioxidative action of oleosins and soy fibers. Lipid oxidation
is a major problem for food manufactures as oxidation products are associated
with decreased food quality in terms of taste, texture, appearance, and shelf life
(Berton-Carabin et al. 2014). Lipid oxidation is a major impediment in enriching
food with polyunsaturated fats, such as fish oil (Kargar et al. 2011; Wijesundera
and Shen 2014). Oleosin, a protein stabilizing oil bodies inside the seeds of oil
plants such as canola, has been shown to not only stabilize emulsions but also to
148 M. Rayner et al.

decrease the rate of lipid oxidation (Wiejesundra 2013). Fish oil-in-water emul-

sions stabilized by oleosin had remarkably lower levels of the oxidation marker
heptadienal, compared to emulsions stabilized by Tween 40 or sodium caseinate.
Furthermore, the depletion of the sensitive fatty acids EPA (eicosapentaenoic acid)
and DHA (docosahexaenoic acid) in the fish oil were lower for the oleosin-stabi-
lized emulsions (20 % of initial value) compared to emulsions stabilized by Tween
40 (70 % of initial value) (Wijesundera et al. 2013). The antioxidative effect is
thought to be due to oleosins’ structure with an amphipathic domain with both
hydrophilic and hydrophobic residues, a fully hydrophobic domain penetrating
into the oil, and a second amphipathic domain situated near the C-terminus. This
arrangement of oleosin at the oil–water interface may act as a barrier to oxygen
and reactive hydroperoxides, preventing the oleosin-stabilized oil droplet from
oxidative deterioration processes (Gray et al. 2010). It has also been demonstrated
that fibers from soy (SSPS) prevents oxidation of oil and flavor oils. The mecha-
nism is suggested to be stabilization of free radicals by the pectic polysaccharides
included in the SSPS structure (Maeda and Nakamura 2009).
In the fruit and vegetable sector, it is desirable to control growth of a wide vari-
ety of microorganisms to prolong the storability of fresh products. Chitosan has
been demonstrated to have potential as an antibacterial and antifungal preserva-
tive, aiding in increasing fruits, and vegetables storability (Shiekh et al. 2013).
Coating the entire fruit with chitosan reduced the respiration rate of cucumber,
strawberries, and tomatoes. The chitosan film also reduced the ripening and des-
iccation rate of strawberries and tomatoes. The antimicrobial effect of chitosan
is suggested to be due to penetration of chitosan into the microbial cells. Inside
the cells, chitosan form a complex with phosphate negative charges of the DNA
helix, hindering further growth (Kubota and Kikuchi 1998). Chitosan is also used
in wound dressings, due to the antimicrobial function. Wound dressing impreg-
nated with a combination of chitosan and alginate are proven to be effective in
controlling bacterial invasion in wounds (Muzzarelli and Muzzarelli 2009). OSA-
modified inulin (In-OSA) has been reported to have antibacterial activity against
S. aureus and E. coli (Zhang et al. 2015). The effect was concentration depend-
ent and 1 % and 0.5 % In-OSA completely inactivated growth of E. coli and S.
aureus, respectively. OSA-modified inulin interacted with the cell walls and cell
membranes of the microorganisms and destroyed them severely, in some cells the
walls was reported to disappear completely (Zhang et al. 2015).

5.4 Regulatory Aspects

Natural polymers added to foods are regulated either as additives or ingredients

where most are classified as additives. Gelatin is an exception and is classified as
ingredient. Ingredients are listed in the products’ list of content with their name,
whereas additives must be listed by a specific number (E-number in the European
Union and INS number international) and it is voluntary if the manufacture wants
5  Application of Natural Polymers in Food 149

Table 5.7  Approved EFSA health claims for products containing natural polymers

Claim Hydrocolloid
Maintenance of normal blood cholesterol Beta-glucan, konjacmannan glucomannan,
concentrations pectins, guar gum
Maintenance or achievement of a normal body Konjacmannan glucomannan
weight
Reduction of postprandial glycaemic Beta-glucan, pectins
responses

to list additives also with their names. Additives are regulated by JECFA (Joint/
WHO Expert Committee on Food Additives) in the US and by the European
Commission within the EU. The regulation is used to protect the consumers’
health and to ensure fair practice in the food trade. The objective of the regula-
tion of additives is to establish safe levels of intake and to develop specifications
for purity of the different compounds. Once accepted, an international number
(INS, International Number System) or an E-number is allocated to the additive
together with a specification of the acceptable daily intake (ADI) which cannot be
exceeded. The INS/E-number is an acknowledgment of its acceptability.
When it comes to health claims of natural polymers as additives, it is regulated
by EFSA (European Food and Safety Agency) within the EU. EFSA is evaluat-
ing available scientific evidence of the health claim and take a decision whether
the evidence is sufficient enough or not. Only health claims approved by EFSA
is legal to market on food packages within the EU. Most applications fail due to
too low quality of the provided studies (Randomized Controlled Trials (RCT) are
preferred), too few studies conducted, or due to too few test subjects in the studies.
However, some natural polymers have passed EFSAs review and have approved
health claims (Viebke et al. 2014) summarized briefly in Table 5.7.

5.5 Market Information

This section aims to provide some market information on the main categories of
natural polymers discussed in this chapter including revenues, volumes, and aver-
ages prices, as well as main application areas, and leading manufactures of the
various types of additives/ingredients. This data is not exhaustive but more to give
an idea of the commercial importance of natural polymers in the food industry.
The world natural polymer market (for all applications including foods) is valued
at ~$4.4 billion US. By total sales, this market consists of ~70 % starches, ~12 %
gelatin, ~5 % carrageenan, ~5 % pectin, and ~4 % xanthan gum, followed by
LBG, alginates, carboxymethylcellulose (CMC), and many others. The total vol-
ume production volume is estimated to be 260,000–300,000 metric tons. It should
be noted that nearly all-natural polymers are also used in nonfood industrial appli-
cations. The main customers being the textile and paper industries which use them
as sizing and coating agents. Nevertheless, there are a few types (e.g., starch,
150 M. Rayner et al.

gelatin, pectin, carrageenan, and some other natural gums), which find their major
applications in foods (Nussinovitch and Hirashima 2013). Despite the fact foods
are often produced in large volumes, the natural polymer ingredients used in for-
mulating them only represent small quantities, since these additives and ingredi-
ents are only required in minor amounts (maximum a few %) to impart the desired
functional properties to these products.
Natural polymers in foods as food additives and ingredients make up a signifi-
cant portion of the Sensory and Textural Food Additives Market. Where sensory
additives are colors and flavors, and textural additives have the function of thick-
ening and gelling agents, as well as emulsifiers and stabilizers. According to Frost
and Sullivan (2013a, b), the total market revenue for the Sensory and Textural
Food Additives Market was over $16 billion USD (US dollars) in 2012, of which
Europe and North America account for 72 % of all sales revenue (see Table 5.8).
Within this market there are several subsegments that are relevant in the context of
natural polymers, specifically, the natural emulsifiers segment, the modified starch
segment (which is considered to be a synthetic additive in market reports) and the
gelling agents segment (Tables 5.9, 5.10, 5.11, 5.12, 5.13).

Table 5.8  Total sensory and textural food additives market: revenue and compound annual rate
of growth (CAGR) by segment and additive type for Europe and North America 2012–2017
(Frost and Sullivan 2013a, b)
Segments Europe North America
Revenue 2012 ($ CAGR Revenue 2012 ($ CAGR
Millions) (2012–2017) Millions) (2012–2017)
Sensory food additives (i.e., colors and flavors)
Natural 991.0 6.3 % 995.1 6.9 %
Synthetic 2062.1 4.0 % 3 665.0 2.4 %
Textural food additives (i.e., emulsifiers, thickeners, gelling agents)
Natural 610.1 7.6 % 470.4 3.5 %
Synthetic 1749.4 3.2 % 1 554.7 4.4 %
Total 5412.6 (32 % of global) 6685.3 (40 % of global)
All values are in US dollars, base year 2012

Table 5.9  Modified starches market sub-segment revenue and pricing trends for Europe and
North America 2012–2017 (Frost and Sullivan 2013a, b)
Additive Europe North America
Revenue CAGR Price per kg Revenue 2012 CAGR Price per kg
2012 ($ (2012– (2012, $) ($ Millions) (2012– (2012, $)
Millions) 2017) (%) 2017) (%)
Modified 1100.0 3.8 1050.0 5.2
Starches
Potato 1.7–2.0 –
Maize 1.4–1.7 1.4–1.7
Wheat 1.2–1.4 1.2–1.4
Rice – 1.6–2.0
All values are in US dollars, base year 2012
5  Application of Natural Polymers in Food 151

Table 5.10  Key suppliers of modified starches, company market share ranking 2012 (Frost and
Sullivan 2013a, b)
Europe North America
1. Cargill Inc. 1. Cargill Inc.
2. Roquette 2. Archer Daniels Midland Company
3. Tate & Tyle PLC 3. Tate & Tyle PLC
4. Avebe 4. National Starch
5. National Starch and Chemical Co.

Table 5.11  Gelling agents market sub-segment revenue and pricing trends for Europe and North America
2012–2017 (Frost and Sullivan 2013a, b)
Additive Europe North America Pricing Trends
Revenue 2012 ($ CAGR Revenue CAGR (2012– $ per kg (2012)
Millions) (2012–2017) 2012 ($ 2017) (%)
(%) Millions)
Carrageenan 127.9 2.5 98.0 3.5 10–12
Pectin 114.8 2.5 88.2 3.1 12–15
Xanthan Gum 127.7 2.5 98.0 3.0 5–8
Agar-agar 29.6 2.5 22.9 3.4 20–23
Total 400.0 307.1

Table 5.12  Key suppliers of gelling agents

Company Name Carrageenan Pectin Xanthan gum Agar-

●
agar

● ● ●
FMC Biopolymer

● ● ●
CP Kelco

●
Danisco Dupont

● ● ●
Shemberg Corporation

●
Cargill

●
Jungbunzlauer

●
Hispanagar

●
Industrias ROKO
Iber Agar
Leading global suppliers of gelatin include: Gelita USA Inc., Rousselot Inc., PB Leiner USA,
Nitta Corporation, Kraft Foods Inc., Lapi SpA, Italgelatine SpA, Sterling Biotech, Ewald
Gelatine, Weishardt (Frost and Sullivan 2012)

Table 5.13  Emulsifier market sub-segment revenue and pricing trends for Europe and North
America 2012–2017 (Frost and Sullivan 2013a, b)
Additive Europe North America Pricing trends
Revenue 2012 CAGR Revenue CAGR $ per kg
($ Millions) (2012–2017) (%) 2012 ($ (2012–2017) (2012)
Millions) (%)
Natural 210.1 7.3 163.3 4.1 5–12
emulsifiers
Synthetic 649.4 5.6 504.7 2.8 2–7
emulsifiers
Total 859.5 668.0
152 M. Rayner et al.

Fig. 5.9  Modified starch subsegment market size by end application 2012 (Frost and Sullivan
2013a, b)

5.5.1 Modified Starch Market

Modified starches are primarily used to provide better mouth feel and enhance the
texture of foods, as well as in the stabilization of emulsions and foams. The aver-
age price of modified starch varies between $1.20 and $2.00 USD/kg however, the
price of both modified starches and native starches depends heavily on the pre-
vailing raw material supply and demand in the agricultural commodity markets
(Fig. 5.9).

5.5.2 Gelling Agents Market

Gelatin is not classified as an additive but rather an ingredient as part of the global
animal protein ingredients market. Globally, the volume of animal protein ingredi-
ents was 2.3 million metric tons in 2012 with a compound annual growth rate of
4.8 %. Of this approximately 11.3 % was gelatin selling (0.26 million metric tons)
at an average market price of $7–$8 per kg (Frost and Sullivan 2012). Thus, the
approximate gelatin sale globally is estimated to be in the order of $2 billion USD
per year in 2012.
Multifunctional ability of many hydrocolloids helps them find use in a wide
array of applications. Processed food (including savory), dairy, and bakery are the
most prevalent application areas for gelling agents (Fig. 5.10). All of the hydrocol-
loid based gelling agents are intrinsically “natural.” Carrageenan is mainly used
in processed food and savory products, while pectin is used extensively in bakery
applications, and xanthan gum is used predominantly in dairy and beverage appli-
cation areas (Frost and Sullivan 2013a, b). Historically, animal-based gelatin is the
most commonly used gelling agent, but due to outbreaks of bovine spongiform
5  Application of Natural Polymers in Food 153

Fig. 5.10  Gelling agents subsegment market size by end application 2012 (Frost and Sullivan
2013a, b)

encephalopathy (mad cow disease) as well as religious dietary customs, there has
been substantial interest in substitute sources of gelatin, such as fish skin. The
carrageenan market has also seen introduction of cheaper grades, which can be
used as an alternative in cases where gel clarity is not important (Nussinovitch and
Hirashima 2013).

5.5.3 Natural Emulsifiers Market

The natural emulsifiers market is dominated by lecithin (which is not a polymer),

however, dairy proteins and modified starches are also widely used for emulsion
stabilization but are seen and regulated as protein ingredients or included within
the modified starch segment. Although, the natural emulsifier segment is smaller,
the growth rate is generally higher indicating a shift toward more natural ingre-
dients and additives in general. Furthermore, there are new multifunctional emul-
sions stabilizers being developed from natural sources and this segment will likely
see growth both at the expense of synthetic emulsifiers as well as total volume as
new applications areas open up.

5.6 Future Outlook

The introduction of totally new natural polymers for food use is unlikely as it is
restricted by the large investment cost associated with obtaining the necessary
legislative and regulatory approval. Therefore, it is likely that advancements will
be made with respect to new combinations, applications areas, or technological
154 M. Rayner et al.

advances with respect to processing and manufacture of existing approved natural

polymer-based additives or ingredients.
The use and development of natural polymers in foods is likely to continue
and increase in coming years, however, there may be shifts from one source to
another due to factors like sourcing issues, varying prices, and consumer prefer-
ence changes. Frost and Sullivan (2013a, b) have identified several market drivers
that are increasing the use of textural food additives and ingredients in general and
natural polymers in particular, including:
Adoption of new technologies: The advent of novel technologies such as micro/
nano-encapsulation in the food sector has allowed for the application of many
ingredients, such as modified starches, hydrocolloids, and macromolecular emul-
sifiers to create core shell materials, or even serve both as shell material and as
binding agents that improve process stability and textural properties of the final
product. Micro/nano-encapsulation is used to improve chemical stability or bio-
availability of other sensitive ingredients such as vitamins, functional food ingredi-
ents, and volatile aromas.
A significant shift from synthetic to natural ingredients: Health, wellness, and
well-being are a mega trend where “natural” tags on products has a significant
impact on consumer choice. This has led producers to develop all-natural prod-
ucts or to partially replace synthetic ingredients with natural ingredients/additives
in their product offerings.
Increasing consumption of convenience and performance foods: High growth
in the convenience food and prepackaged food sector has created more opportuni-
ties for natural polymer based textural food ingredients, especially in combination
with the “natural” trend. In addition to convince food, textural ingredients play a
key role in performance foods that tend to rely on specialized and sophisticated
formulations that require functionally advanced ingredients. Although natural
polymers have historically been used in the food industry to control the stability
and improve the texture of food products, many consumers are becoming increas-
ingly aware of their nutritional and health benefits. Examples include maintain-
ing appealing texture in low-fat food products, prebiotics, and the use of structural
approaches to enhance satiety.
In addition, the classical use of natural polymer in formulations, the manufacture
of natural polymer-based microgels is likely to see an increase as well. This is
due to the fact that microgels have potential in fat replacement as well as rheol-
ogy and texture control, and they can be tuned for encapsulation, targeted deliv-
ery, controlled release, and satiety control applications (Shewan and Stokes 2013).
Although it is believed that industrial scale manufacture is achievable for micro-
gels in the food industry (as many processes are based on standard dairy unit-oper-
ations such as heating, shearing, membrane filtration, and spray drying), there is
still considerable capacity for major advancements with respect to their manufac-
ture and novel application areas.
5  Application of Natural Polymers in Food 155

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Chapter 6
Current Application and Challenges
on Packaging Industry Based on Natural
Polymer Blending

S.T. Sam, M.A. Nuradibah, K.M. Chin and Nurul Hani

6.1 Introduction

Currently, the packaging sector is a major consumer in the most industries. Plastic
packaging is being increasingly used in medical products and healthcare as well as
in the beverages and packaged foods. In year 2002, large amounts of different syn-
thetic plastics, totaling about 200 million tons per year, are produced throughout
the world (Zhang et al. 2002). Among them, packaging is the largest single market
for plastics, about 12 million tons per year. Another statistic released by Pardos
Marketing, an industrial market research company which specializes in plastics
and their applications, shows that the global consumption of plastics in 2005 com-
prises mainly of packaging plastic, up to 33 million tons, polyethylene, whereas
4.8 million tons composed of polypropylene (Anonymous 2005).
The demand of synthetic petrochemical-based polymers as packaging materials
has been rising because of their desirable mechanical properties, and thermal sta-
bility as well as their performance as good barriers to carbon dioxide, oxygen, and
aromatic compounds. The main reasons why synthetic petrochemical-based poly-
mers are being chosen as packaging materials are because of their relatively low
cost and large availability. Although the synthetic petrochemical-based polymers
have been widely used in a variety of packaging materials, the disadvantage is that
they become a major source of waste after use due to their poor biodegradability.
Hence, due to the increasing demand in the packaging industries with a concern of
the environmental issue, the usage of natural polymers to produce biodegradable
packaging materials is the correct action in terms to reduce waste disposal prob-
lems and to guarantee the quality of the product (Sam et al. 2014).

S.T. Sam (*) · M.A. Nuradibah · K.M. Chin · N. Hani 

School of Bioprocess Engineering, Universiti Malaysia Perlis,
Kompleks Pusat Pengajian Jejawi 3, 02600 Arau, Perlis, Malaysia
e-mail: stsam@unimap.edu.my

© Springer International Publishing Switzerland 2016 163

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_6
164 S.T. Sam et al.

Table 6.1  Benefits of natural – Biodegradable

polymer-based packaging – Supplement the nutritional value for foods
materials
– Reduced packaging volume, weight, and waste
– Incorporated antimicrobial and antioxidants
– Low cost and abundant
– Annually renewable resources

These degradable packaging options can be produced from two major types of
natural sources:—(1) polysaccharides—such as starch, cellulose, chitin, and chi-
tosan; and (2) proteins—such as soya, wheat gluten, and collagen/gelatine; derived
from plant and animal resources as the substitution for their non-biodegradable
petrochemical-based counterparts. Table 6.1 shows the advantages of natural poly-
mer-based packaging materials.
Normally, industries’ techniques to produce packaging-based natural polymers
are injection moulding and blown film extrusion. Injection molding is a method
to obtain molded products by injecting plastic materials molten by heat into
a mold, and then cooling and solidifying them. The method is suitable for the
mass production of products with complicated shapes, and takes a large part in
the area of plastic processing. This type of technique is applied in food packaging
industries.
Blow molding is a molding process in which air pressure is used to inflate soft
plastic into a mold cavity. It is an important industrial process for making one-
piece hollow plastic parts with thin walls, such as bottles and similar containers.
Since many of these items are used for consumer beverages for mass markets,
production is typically organized for very high quantities. The technology is bor-
rowed from the glass industry with which plastics compete in the disposable or
recyclable bottle market. The application for natural polymers blending is widely
used in food packaging, bottles packaging as well as in medical/pharmaceutical
industries.

6.2 Sources of Natural Polymers to Produce Packaging

6.2.1 Polysaccharides

Starch, cellulose, chitin or chitosan, and pectin contribute to the formation of poly-
saccharide films. The impart hardness, crispness, viscosity, and gel forming ability
to produce a variety of films. The nontoxic properties allow the biodegradation by
enzymes and do not produce environmentally harmful byproducts. It also exhib-
its excellent gas permeability properties that improve the shelf life of the product
without creating anaerobic conditions. Basically, the hydrophilic and composition
of the polymeric chains that exhibit low moisture barrier properties is known as
polysaccharide-based products (Coma 2013).
6  Current Application and Challenges on Packaging Industry … 165

6.2.1.1 Starch

Starch is a natural polysaccharide that accumulates in plant seeds, leaves, tubers,

and stalks. The main sources for the commercial production of starch are potatoes,
corn, wheat, and rice. Starch has two main polymeric constituents which are amyl-
ose in which the glucose units are 1,4-α-D-linked together in straight chains and
amylopectin in which the glucose chains are highly branched of 1,4-α-D-linked
and 1,-α-D-linked glucose residues as shown in Figs. 6.1 and 6.2 (Bertuzzi et al.
2007).
Table 6.2 shows the amylase and amylopectin content in natural starches.
Starch is one of the less expensive biodegradable materials used for many non-
food items such as textile sizing, cardboard, and paper making. In recent times,
starch has been employed as the major polymer in thermoplastic compositions
and has been processed into various materials such as utensils and it also has been
used as raw material for film production (Canigueral et al. 2009).

CH 2OH CH 2OH

O O

O O

HO OH HO OH

Fig. 6.1  Amylose 1,4-α-D-linked glucose unit

HO
O

HO CH 2OH

CH 2OH O CH 2OH

O O
CH2

O O O O

HO O OH HO
HO OH OH

Fig. 6.2  Highly branched amylopectin

166 S.T. Sam et al.

Table 6.2  Amylose and Amylose (%) Amylopectin (%)

amylopectin content in
Potatoes 23 77
starches (Veronica 2013)
Wheat 20 80
Rice 15–35 65–85
Corn 25 75
Banana 17 83

The proportions of amylose and amylopectin in starch depend on the source,

amylose content ranges from 10 to 20 %, and that of amylopectin is 80–90 %.
Amylose is soluble in water and appears as a helical structure, whereas amylopec-
tin chains are crystallized helical structure and cause the starch to occur physically
as discrete granules. The starch granules show hydrophilic properties and strong
intermolecular group through hydrogen bonding formed by the hydroxyl groups
on the granule surface (Pillai et al. 2005).
Pure starch is a white, tasteless, and odorless powder and it is insoluble in cold
water and alcohol. Starch can be used as a gluing or as thickening agent because
it can dissolve in warm water. For starch-based materials, it is extremely brittle
and has poor mechanical properties for packaging material. Starch alone cannot
form films with suitable mechanical properties (high percentage elongation, ten-
sile, and flexural strength) unless it is plasticized, blended with other materials,
chemically modified, or modified with a combination of these treatments. Frequent
plasticizers used include glycerol and other low-molecular-weight polyhydroxy
compounds, polyethers, and urea (Peelman et al. 2013).
Starch is a fully biodegradable polymer where it can hydrolyze into glucose via
microorganisms or enzyme and after that it will be metabolized into carbon diox-
ide, CO2, and water, H2O (Lu et al. 2009). The starch itself has poor mechani-
cal properties; this limitation is overcome by blending with other polymers. To
prepare completely biodegradable starch-based biocomposites, starch is usually
blended with aliphatic polyesters (PLA and PHA), polyvinyl alcohol (PVA), and
other types of biopolymers. The most common polyesters to be used with starch is
poly(β-hydroxyalkanoates) (PHA), which is obtained by microbial synthesis, and
polylactide (PLA) or poly(ε-caprolactone) (PCL), which is derived through fer-
mentation and chemical polymerization, respectively (Wang et al. 2008).
For starch-based materials, the hygroscopic properties depend on the tem-
perature, relative humidity, RH, and nature of the substituent. The availability of
hydroxyl groups on the starch chains has potential to display reactivity specific to
where they can oxidize and reduce and might take part in the formation of ethers,
esters, and hydrogen bonds (Tomasik and Schilling 2004).

6.2.1.2 Cellulose

Application of cellulose nanofibers in polymer reinforcement is a relatively new

research field. Cellulose is the most abundant organic molecule on earth, since it
6  Current Application and Challenges on Packaging Industry … 167

Fig. 6.3  Chemical structure HO
of cellulose OH

HO O
O

O
O HO O

HO
OH

is the main component of plant cell walls like cotton, hemp, and other plant-based
material. Uniquely, cellulose also can be synthesized by algae, tunicates, and some
bacteria (Iwamoto et al. 2007). The glucose units in cellulose are linked by gly-
cosidic bonds, but there are different α glycosidic bonds found in glycogen and
starch. Cellulose has more hydrogen bonds which make it tougher fiber compared
to glycogen or starch.
Regardless of its virtual chemical simplicity, the physical and morphologi-
cal structure of native cellulose in higher plants is complex and heterogene-
ous. Besides, the molecules of the cellulose are thoroughly connected with other
lignin and polysaccharides which cause more complex morphologies. It is a lin-
ear polymer of β-1,4-linked d-glucose between the anhydroglucose repeating units
that contain highly ordered crystalline regions with more disoriented amorphous
parts. Due to their high stiffness, strength, biodegradability, renewability, and light
weight, the application and production of nanoscale cellulose fibers in composite
materials have gained much attention (Kamide 2005).
The limited application of cellulose nanofibers to date may be due to the sepa-
ration of plant fibers into smaller basic element which is a challenging process.
Besides the nature of starch is hydrophilic, the packaging materials from this
material have low water vapor barrier that causes poor mechanical properties and
limited long-term stability. Addition of cellulose fibers to starch-based films will
reduce 35 % of the water vapor permeability after plasticized with glycerol and
decreased about 14 % after the addition of cellulose fiber. The tensile strength and
Young’s modulus will increase without changing the value of elongation at break
(Dias et al. 2011). Figure 6.3 shows chemical structure of cellulose.

6.2.1.3 Chitin and Chitosan

The most abundant polysaccharide on earth after cellulose is chitosan. Chitosan is

produced from chitin by deacetylation to remove the acetyl group. Chitin is a main
constituent of the shells of crustaceans like crab, shrimp, and crawfish. It is inex-
pensive, biodegradable, biocompatible, and nontoxic. Compared to chitin, chitosan
168 S.T. Sam et al.

is more versatile due to its structural features and potential to develop films, hav-
ing different properties and barriers (Fernandez-Saiz et al. 2010).
Chitosan is the second most abundant polysaccharide on earth after cellulose.
This biopolymer is mostly available from waste products in the shellfish indus-
try, and therefore commercial supplies are currently in abundance. It can also be
acquired from fungal cell walls of the chitin component. There are three reactive
functional groups chitosan which are amino/acetamido group, primary hydroxyl
group, and secondary hydroxyl group at positions of C-2, C-3, and C-6, respec-
tively. The main reasons for the differences between their physiochemical and
structural properties are the amino contents (Chen et al. 2008a, b).
The properties of chitosan are biocompatible, biodegradable, and nontoxic
which make it a suitable material for packaging films. Besides the positive charge
of chitosan, it readily binds to negative-charged surfaces thus making chitosan a
bioadhesive material. The presence of NH2 causes the reaction of chitosan much
more versatile compared to cellulose (Rinki and Dutta 2008). Chitosan is read-
ily soluble in dilute acidic solutions less than pH 6.0. Chitosan possesses primary
amino group with a pH value of 6.3 and that can be considered as a strong base.
The pH significantly changes the charged state and properties of chitosan due the
presence of amino groups. Starch and chitosan blends exhibit good film prop-
erty which featured to intramolecular and intermolecular hydrogen bondings that
appeared between amino and hydroxyl groups on the backbone of two compo-
nents (Lu et al. 2009).

6.2.2 Proteins

6.2.2.1 Soya

Soya products including soya powder and soya concentrate are commercially
available. The cost of soya powder is cheaper than other soya products such as
soya protein concentrate and soya protein isolate. In fact, the soya powder is
similar to polysaccharide-based natural polymer as it is hydrophilic in nature.
According to Swain et al. (2004), the soya beans contain 18–20 % of oil, 40–55 %
of protein, 25–30 % of carbohydrate, and 3 % others. Figure 6.4 shows the major
constituents of soya bean uses.
The soya bean began to gain popularity in Asia starting in the mid 1960s. The
awareness of the soya beans as a low-cost and high-quality fortifier for traditional
grains, primarily the weaning foods, increases the demand of soybeans. The pro-
duction of the soya beans to become flour or powder has undergone several pro-
cesses (David et al. 2006).
The soya powder which is a byproduct in the commercial extraction process of
soya protein isolate (SPI) seems to have high protein compared to other flour as it
is produced from carbohydrate-rich grains. The whole soya bean was heated and
grinded with hammer mill, and 97 % will pass through a mesh screen. The flour
6  Current Application and Challenges on Packaging Industry … 169

SOYBEANS

WHOLE SOYBEAN
PRODUCTS

DEFATTED SOYBEAN OIL

SOY FLAKES

PAPER COATING PRINTING INK PAINT AND PLASTIC AND

VARNISH RESIN

Fig. 6.4  Major constituents of soya bean uses (Swain et al. 2004)

that passing through the finest mesh screen has the highest protein content and the
moister heat treatment produces more quality and nutritional value (David et al.
2006).
Soy-based plastics can be divided into two main segments which are polyure-
thane using soy polyols and thermo sets. Each segment has great growth potential,
from the farmers who grow the soybeans to the manufacturers who utilize them to
the end user who benefits from a high-quality product (Stepto 2006).
The first documented work in producing plastic from renewable resources came
from Henry Ford around 1910. He was interested in making plastic from plastic waste
and he succeeded in 1940 by producing a ‘plastic car’ from soya bean waste mixed
with other components to increase strength. Then, a new awareness in relation to the
human impact on earth gave way to do research in the area of plastic. The alternative
way that has been taken is by producing biodegradable plastics (Narayan 2009).
As more manufacturers look for options to high petroleum prices, soy-based
plastics offer a possible choice. The multipurpose and lower production costs
make soy plastics the main area for rapid growth.

6.2.2.2 Wheat Gluten

Plant protein from wheat such as wheat glutenins is the abundant co-product
with low price that derive from readily available resources and it is biodegrada-
ble. Wheat is one of the three most important crops in the world which include
maize and rice. India becomes the second largest producer of wheat in the world.
The main components of groups in wheat are starch and protein. Wheat gluten
is a large extended polypeptide polymer without globular structure (Shewry and
Halford 2002).
170 S.T. Sam et al.

Table 6.3  Wheat protein classification based on solubility (Wieser 2007)

Groups Proteins Function Molecular Solubility Distribution Average
weight protein
content (%)
Non- Albumins Metabolic 20,000 Water Embryo 15
gluten and cyto-
proteins plasmic
proteins
Globulins Storage 20,000– Dilute salt Embryo and
and cyto- 200,000 solutions aleuronic
plasmic layer
proteins
Gluten Gliadins Storage 30,000– Ethanol Endosperm 45
Proteins proteins 60,000 (70–80 %)
Glutenins Storage 8000 Dilute 40
proteins several acid/alkali
millions solutions

The term “gluten” mainly refers to the proteins due to the role in determin-
ing the unique baking quality of wheat by conferring water absorption capacity,
cohesiveness, viscosity, and elasticity on dough. Basically, wheat gluten is attained
when the wheat dough is washed to remove starch granules and water-soluble
constituents. It contains hundreds of protein components that are present either as
monomers or linked by interchain disulfide bonds as oligo- and polymers (Lagrain
et al. 2010).
Table  6.3 shows the classification of wheat gluten based on the solubility.
Basically, they are classified into two main groups which are non-gluten proteins
and gluten proteins. Gluten proteins show low solubility in water or dilute salt
solutions due to the presence of nonpolar amino acid. Besides, it is also due to the
presence of high amount of glutamine and proline residues as it has nonpolar side
chains (Wieser 2007).
There are about 75 % proteins with 35–45 % glutenins and 40–50 % gliadins
content in industry. The difference between gliadins and glutens is that gliadins
have a single-chain polypeptides whereas glutenins have multiple-chain polymeric
proteins that interlinked by intermolecular disulfide and hydrogen. Wheat gluten
can fully degrade without releasing toxic products, so it is the best candidate to
develop biodegradable materials (Yuan et al. 2010).

6.2.2.3 Collagen/Gelatine

Gelatine is generally produced by partial hydrolysis of collagen that was extracted

from the bones, connective tissues, organs, and some intestines of animals.
Gelatine is a translucent, colorless, odorless, brittle, and nearly tasteless solid
substance, derived from the collagen inside animals’ skin and bones. It is a high
6  Current Application and Challenges on Packaging Industry … 171

Fig. 6.5  Composition of Carbon Oxygen

gelatine Nitrogen Hydrogen

7%

17%

51%

25%

molecular weight polypeptide composing of amino acids mainly glycine (27 %),

hydroxyproline, and proline (25 %) (Iwai et al. 2005).
Pie chart in Fig. 6.5 shows the composition of gelatin. It is composed of 50.5 %
carbon, 25.2 % oxygen, 17 % nitrogen, and 6.8 % hydrogen. Gelatine consists of
rigid bar resembling molecules that are arranged in fiber and interconnected by
covalent bonds. These molecules have three polypeptide chains arranged in a triple
helix that is stabilized by hydrogen and hydrophobic bonds (Wang et al. 2012).
Gelatine has unique functional properties which make it widely used in cos-
metic, pharmaceutical, cosmetic, food, and packaging industries. However, the
pure gelatine is brittle and has high moisture absorption. Therefore, gelatine is
usually blended with other polymers to prevail over the weakness. For example,
blend of gelatine with hydrophilic molecules like chitosan could significantly
improve the properties (Lin et al. 2012).

6.3 Industries’ Techniques to Produce Packaging-Based

Natural Polymers

6.3.1 Injection Molding

Injection molding is a process where polymers are heated to an elevated plas-

tic state and pushed at a high pressure into a mold cavity, which subsequently
causes the polymer to solidify into a desired shape. The molded part, or better
known as the molding, will then be removed from the cavity. Figure 6.6 depicts
the process of injection molding which starts from clamping, injection, cooling,
and finally ejection of the product. The cycle of production commonly varies in
between 10 and 30 s, but cases of cycle that exceed one minute are not uncom-
mon. Multiple moldings can be produced per cycle as the mold can have more
than one cavity. Figure 6.7 shows a typical 2D drawing of an injection molding
machine which consists of two major segments, injection segment and clamping
172 S.T. Sam et al.

Clamping Injection Cooling Ejection

Fig. 6.6  Process cycle of injection molding

Fig. 6.7  Injection molding machine

segment. In manufacturing process, this method is the most popular method in

fabricating plastic parts which varies greatly in their complexity, size, and applica-
tion. For example, injection molding is used to fabricate thin-walled plastic parts
such as plastic housings, which are then used in a variety of materials including
consumer electronics, household appliances, power tools, automotive dashboards,
and medical devices such as syringes and valves. Open containers such as buck-
ets and items such as toothbrushes and plastic toys are also products made from
injection molding. It can be said that injection molding is generally the most com-
mon molding process in thermoplastic manufacturing. One of the main advantages
of injection molding is the possibility of producing intricate and complex-shaped
products and it is also very precise. However, this method is only feasible when
there is a requirement for mass production of products with complicated shapes
as this process is costly. In addition, thermoplastic moldings may contain defects
such as weld lines, shrinkage, splash marks, and distortion but corrective measures
and control of the process itself usually play a vital part in achieving an excellent
quality product.
Recently, many researchers have utilized lignocellulosic filler to replace con-
ventional fiberglass fillers in thermoplastic composites in manufacturing plas-
tic parts (Nourbakhsh et al. 2011; Rahman et al. 2011; Azaman et al. 2013).
Processing temperature of lignocellulosic thermoplastic composites is usu-
ally below 230 °C in order to prevent/reduce fiber degradation (Sanadi et al.
1998). A study had been conducted by Azaman et al. (2014) on the suitability of
6  Current Application and Challenges on Packaging Industry … 173

lignocellulosic polymer composites in forming a shallow, thin-walled part mold

with minimal residual stress distribution with injection molding method. There
are three important parameters involved which are the mold temperature, cooling
time, and packing pressure, and the optimal conditions for each of the parameters
had been investigated. From the report, it had stated that if the mold temperature
is too low, crystallization problems start to occur but if the mold temperature is
too high, the properties of lignocellulosic polymer composites will degrade. An
increase in cooling time will cause a drop in the tensile residual stresses near the
wall of the mold while an increase in packing pressure will create higher inner
stresses within the parts. Therefore, through numerical distribution analysis done
by the authors, they had found out that the optimum parameter range for the mold
temperature would be around 40–45 °C. As for the cooling time, the optimal range
is between 20 and 30 s while the optimal packing pressure is 0.85Pinject.
Yuqiu et al. (2012) studied on pultrusion technique to produce long fiber bio-
composite pellets which comprises jute fiber and poly(lactic acid), a biodegradable
thermoplastic matrix, for the purpose of injection molding. Jute/PLA composites
were successfully fabricated by injection molding process and its mechanical
properties were then investigated. It was reported that 250 °C molding temperature
is the most suitable temperature for pultrusion process of jute/PLA long fiber pel-
lets because of several factors which include less degradation of jute due to heat,
improved impregnation and production efficiency as well as satisfactory mechani-
cal properties. In addition to this, with the incorporation of jute fibers, the ten-
sile modulus and the izod strength had improved but the tensile strength suffered
a slight drop. This suggests that injection molding method has the capability to
produce high-quality products that are environmental friendly as it can fabricate
products made from natural polymers.
A 100 % natural-based biocomposite formed by blending egg albumen (EA), a
natural source of protein with chitosan (CH), a source of glycerol was successfully
made through injection molding method (Martín-Alfonso et al. 2014). In particu-
lar, CH acted as a physicochemical modifier additive in different concentrations
of blends. The general idea of fabricating this biocomposite is to improve the suit-
ability of these composites for specific applications and its properties. From the
results shown in the report, the DMTA spectra were found out to be comparable
to low-density polyethylene (LDPE), a commercial polymer. EA/CH composites
had showed intensified behavior at high temperature when compared to LDPE.
Tensile strength and elongation at break were reported to decrease with increas-
ing CH content. The glass transition temperature, Tg, of the composites as well as
the water absorption capacity was reduced. Biocidal activity against gram-negative
bacteria (E. coli) was not significant. From the results, it can be deduced that there
is an apparent limitation of these biocomposites in areas such as food packaging
but the low diffusion efficiency of chitosan had opened up the possibilities in areas
such as surgical dressings, water filtration, fruit coating, tissue engineering, and
drug encapsulation.
Another innovative process that is widely used in plastic manufacturing
industry to enhance molding quality using a lower amount of polymer is the
174 S.T. Sam et al.

gas-assisted injection molding process. The principle of operation is basically to

void out the thick internal sectional area with high-pressure gas injection to fur-
ther lower down the use of polymers as compared to the conventional method.
The gas acts on the molten resin by pushing it forward and then keeps it at high
pressure during cooling. Over the past years, researches on this particular method
had been focused only on conventional petroleum-based polymers in areas such
as filling simulations (Chen et al. 2008a, b), gas channel design (Marcilla et al.
2006), and molding quality (Castany et al. 2003). However, Yam and Mak (2014)
had successfully extended this gas-assisted injection molding process by utilizing
eco-composites polymers made from rice husk-filled polypropylene in dissimi-
lar compositions. The weight ratio of the product made from this technique had
reduced a total of nearly one-third of the weight ratio of the product made through
conventional injection method, which indirectly lower the amount of petroleum-
based polymer required. It was also reported that this method also reduced the
mold clamping force and injection pressure used, which in turn saved up a total
20 % energy cost. This approach had not only utilized an agricultural waste to
minimize the dependency of petroleum-based polymer, but also help to reduce
environmental problems and increase the manufacturers’ economic benefits.

6.3.2 Blown Film Extrusion

Blown film extrusion process is one of the most common polymer packaging
processes in the world. Figure 6.8 shows a general blown film extrusion process,
where thin-walled tube was formed from the vertical extrusion of plastic melt
through an annular slit die. At the center of the die, air is introduced to blow up
the tube like a balloon. A high-speed air ring, which is mounted on top of the
die, cools the hot film by blowing air onto it. The tube of film is continuously
cooled down as it moves upward until it is flattened by nip rolls to create ‘lay-flat’
tube of film. This lay-flat tube is then moved down the extrusion tower via roll-
ers. Polymers such as low-density polyethylene and high-density polyethylene are
the common plastic materials used in blown film production. Typical applications
of the blown film product include industry packagings such as shrink film, stretch
film, and bag film, and also consumer packagings such as food wrap film, fill &
seal packaging film, and packaging bags. Blown films are also being utilized in
other areas such as medical and agricultural industries.
The possibility of thermoplastic starch films made from blown film extru-
sion technique had gained interest of researchers over the past decade. Mats et al.
(2008) had successfully investigated the suitability of TPS made from the mixing
of potato starch, glycerol, and water on blown film extrusion method. The results
on melt tenacity showed that plasticizer such as glycerol is important in order for
the extrudate to expand satisfactorily. The tendency for bubbles to form in the
extrudate and rupturing of the stretched melt portrayed the weakness of this mate-
rial for this particular method. However, Olivia et al. (2013) successfully showed
6  Current Application and Challenges on Packaging Industry … 175

Fig. 6.8  Process flow diagram of an extrusion blown film (Li et al. 2014)

that natural polymeric films that are suitable for food packaging applications can
be developed by this blown film extrusion technique through the development of
films made from native and acetylated corn thermoplastic starches (TPS). The
processability of the films had been proven by the ability to withstand the airflow
pressure and the tension exerted by rolling, without signs of tearing of the films.
The blowing process used had developed homogeneous films without defect/bub-
bles on all TPS formulations, supported by visual observation and SEM imaging.
However, the films appeared to be sticky due to the exposure to a humid environ-
ment and the nature of glycerol being hydrophilic. Acetylated corn TPS had lower
water vapor permeability than native corn TPS. As for gas permeability, all films
presented selective gaseous permeability which can be proven useful in developing
food packaging materials. An increase in tensile strength and a decrease in flex-
ibility and water vapor permeability were shown by the films that were stored in a
controlled environment of 20 °C and 65 % RH.
Although there is a bright future for packaging materials to be made solely
from plasticized starch (TPS) through blown film technique, the limitations in
their mechanical and water barrier properties had restricted their areas of utiliza-
tion. Patrícia et al. (2014) developed a novel approach to use natural biodegradable
polymer, poly(butylene adipate-co-terephthalate) (PBAT) with citric acid (CA)
as a compatibilizer with TPS made form cassava starch in an effort to improve
these properties. PBAT was known to be flexible and able to fully degrade in a
span of few weeks through enzymatic actions (Ren et al. 2009). The authors also
studied the effect of uncatalyzed and catalyzed CA on the properties of the blown
films. The catalyst used in their experiment, sodium hypophosphite (SHP), had
enhanced the action of citric acid in the microstructure of the blown films and their
176 S.T. Sam et al.

tensile strength and modulus. TPS/PBAT films with catalyst show higher thermal
stability than uncatalyzed films. Most importantly, the reactive extrusion pro-
cess was smooth and efficient when it comes to films with CA which acted as a
compatibilizer.
Thermally imposed shrinkage is a common issue when it involves shrink films
produced through blown film technique. Supak and Sirilux (2011) had attempted
to reduce shrinkage of blown films by incorporating natural runner (NR) latex
in low-density polyethylene (LDPE) to form LDPE/NR composite films. It was
found that with increasing NR content, the degree of crystallinity also showed
similar trend as well. This result was due to the semicrystalline LDPE acting as
a nucleating agent, which then induced crystallization of the NR phase during
the blown film process. The impact resistance and tear strength improved with
increasing NR latex content but the mechanical properties such as tensile strength
and hardness of LDPE/NR composite films declined. Heat shrink ability test was
employed to determine the shrink ability of the LDPE/NR composite films and
the results showed increased shrink ability with higher NR content. Since NR pos-
sesses a higher entropy level, heat was applied to the films. The films were able to
recover to its original form.

6.3.3 Drawbacks in Industrial Techniques to Produce

Packaging-Based Natural Polymers

There are several drawbacks that the polymer processing industry will face when
packaging-based natural polymers were to be produced in an industrial scale.
Generally, natural-based polymers such as starch, cellulose, chitin, and protein
might face microbial and dust contamination due to their prolonged exposure to
the external environment during the period from collection, transport, and stor-
age up until the point of processing (Kulkarni et al. 2012). The difference in each
batch of raw materials used is also one of the disadvantages as natural polymers
may come in different physical and chemical compositions due to the difference
in climate, geography, collection, and storage time (Oliviero et al. 2010; Kulkarni
et al. 2012). Hence, the production output from the process will be greatly affected
due to the inconsistency in terms of physical, mechanical, and chemical proper-
ties of the raw material. Natural polymers are also sensitive to high temperature,
causing degradation to occur during the processing. For example, a film of oat
starch was produced using two methods which are solution casting and blown
film extrusion (Galdeano et al. 2009). In comparison, both the films showed dras-
tic difference in terms of tensile strength as the films produced through casting
method were approximately eight times higher than films that were produced
through extrusion method. As compared to solution casting, it was reported that
the higher temperature employed during the extrusion processing, coupled with
shear stress, had caused degradation of the starch chains to occur, and thus affect-
ing the mechanical properties of the film. Similar results were also obtained when
6  Current Application and Challenges on Packaging Industry … 177

equal parts of soy protein blended with acetylated high-amylose corn starch were
injection molded, where sample degradation starts to occur at temperature above
150 °C (Huang et al. 1999). In another case, the feasibility of producing thermo-
plasticized blown film of zein which is typically found in corn and classified in the
class of prolamine protein was investigated (Oliviero et al. 2010). From the tensile
results in the report, only one batch of the thermoplasticized zein-based material
was able to form film with excellent tensile properties. Protein agglomeration and
the lack of α-helical structures in the films were reported to be the contributing
factors in the decrease in film quality in terms of mechanical strength. In addition,
the inconsistency in the properties of the films obtained for each batch of process-
ing had further proved the downside in utilizing blown film extrusion technique
for natural polymers. Next, complications during injection molding in terms of
mechanical constraint were clearly shown due to the lackluster characteristic of
sunflower oil cake in terms of plasticity behavior, which is a natural polymer made
up of mixture of lignocellulosic fibers and proteins (Rouilly et al. 2006).

6.4 Application of Natural Polymers Blending

in Packaging Industries

6.4.1 Food Packaging

Biodegradable films have the ability to reduce, or completely replace some tra-
ditional polymeric packaging materials for specific applications. Naturally, bio-
degradable packaging materials were produced from natural polymers that are
capable of being degraded by microorganisms (bacteria, fungi, and algae) through
composting processes to produce breakdown compounds such as carbon dioxide,
water, methane, and biomass. To compete with the existing food packaging, hence,
bio-based packaging must perform such as conventional packaging and present
all the requirement functions of containment, protection, preservation, informa-
tion, and convenience in a legally and environmentally compliant manner, and
cost-effectively.
Biodegradable polymers from natural source were divided into two groups:
those which are non-edible and edible. Biodegradable materials derived from
food resources such as polysaccharides, proteins, and lipids are edible; various
researches have been reported due to their potential abilities to replace traditional
plastics and act as food contact edible films and/or coatings. Table 6.4 illustrates
the potential source to produce food packaging.
An edible/biodegradable film is produced from food-derived ingredients in a
thin layer using wet or dry manufacturing processes. The resulting film should be
a free-standing sheet used over the food as wrapping or could be used between
food components for separation. In contrast, edible coatings are materials which
can be applied directly to the surfaces of food products by dipping, spraying, or
panning. Edible packaging formats can be consumed with, or as part of, the food
178 S.T. Sam et al.

Table 6.4  Sources of food packaging (Hanani et al. 2014)

Non-edible Edible
Starch + PE Polysaccharides Protein Lipid
Polysaccharides Chitin/Chitosan Collagen/gelatins Bees wax
Polylactic acid (PLA) Starch Soy proteins Carnauba wax
Wheat gluten Free fatty acids
Polyvinyl alcohol Pectines Whey Oils
Corn zein

product in question, but they may fulfill other functions like acting as carriers for
target food additives (antimicrobial agents, antioxidants, flavorings). Edible films
and coatings may also be used to inhibit migration of moisture, oxygen, and car-
bon dioxide, and/or to improve the mechanical integrity or handling characteristics
of the food (O’Sullivan et al. 2006). Table 6.4 summarizes about the natural poly-
mers and its blends that can be applied in the food packaging industries.

6.4.2 Pharmaceutical Industries

Pharmaceutical packaging can be described as the technology to protect the prod-

ucts for distribution, storage, and until the process involved in the finishing of
pharmaceutical products. Packaging of pharmaceutical products is important in
the maintenance of their quality and effectiveness. Thus, all packaging materials
must be carefully evaluated via testing of selected materials, sterilization, storage,
and stability studies (Singh et al. 2011). Table 6.5 describes about the functions of
packaging for the pharmaceutical industries.
In maintaining the quality of products, the type of materials used for packag-
ing must not produce any adverse affect on the quality of pharmaceutical product

Table 6.5  Functional parameters of eco-friendly pharmaceutical packaging material

Parameters Description
Barrier Protection Provides protection against moisture, light, oxygen and temperature
variations
Biology protection Provides protection against biological contaminants
Physical protection Ensures protection against any physical damage
Information Conveys information on the correct usage of dosage forms, their
communication contents, their provenance, side effect, and warnings
Identification Easy identification of the product
Security Protection from small children and against counterfeiting
Convenience Increase consumer access to products and improve distributions,
handling, selling, and using such products
Marketing Differentiate a product and/or to convey a certain message or brand
image to highlight the pharmaceutical aspects for consumers
6  Current Application and Challenges on Packaging Industry … 179

through absorption, chemical reactions, or leaching of packaging materials. In

addition, it must also be fabricated with minimal complexity, low cost, and good
consumer acceptance (World Health Organization 2003).
There is much concern for eco-friendly, natural resource-based packaging in
the pharmaceutical industry. Advent of new technology has promoted the biode-
gradable packaging as cost-effective materials. This has indeed prompted many
companies to switch over to biodegradable packaging. However, the development
of eco-friendly pharmaceutical packaging materials technology is still in the phase
of growth.
Various development projects and research exist at the early stage targeted at
developing biodegradable and eco-friendly packaging materials. Thus, the design
of the packaging needs to meet the standard requirement to compete with the
existing packaging materials. There has been relatively limited focus on develop-
ing packaging for pharmaceutical industries compared to food packaging. Rubber
and cellulose have received the bulk of the attention to produce pharmaceutical
packaging. Rubber is obtained from latex found in the sap of some plants. It is
used in pharmaceutical packaging as closures (Cooper 1974). Among the derivates
of cellulose, cellulose acetate is widely used in pharmaceutical packaging and
other laboratory works (Haugaard and Festersen 2000).

6.4.3 Plastics Packaging

The biodegradable plastic market is gradually gaining significance in the vast

global packaging industry. Rising concerns over environmental hazards, car-
bon emission, and waste reduction lead toward ‘green packaging,’ which are the
factors likely to boost the market for biodegradable plastic packaging solutions.
Contributing further to the growth of the biodegradable plastic packaging market
includes consumers’ and retailers’ acceptance for eco-friendly packaging; sup-
port for biodegradable bottle and biodegradable packaging from retailers; and
escalating oil prices boosting the demand for alternative packaging materials.
Furthermore, manufacturers are opting for better materials made from renewable
sources for packaging purposes thus keeping them out of the landfills.
Environmental friendliness and sustainability have become basic qualify-
ing criterions for all packaging products. In this regard, the biodegradable plas-
tic packaging market is at a distinctive advantage since biodegradable plastic
naturally has properties which make it one of the easiest materials to recover and
recycle, or else decompose in nature. Biodegradable plastic packaging has a com-
petitive advantage over other packaging materials, which makes it easier to recy-
cle, reduce, and reuse to raise its eco-friendly profile. Table 6.6 shows the various
literature reports on the potential sources of natural polymers blends that can be
used in the packaging application. Blends from the natural polymers are classified
as the polymer that is easy to biodegrade; hence, their usage in packaging indus-
tries should be expanded.
180 S.T. Sam et al.

Table 6.6  Literature reports on the potential source of natural polymers blends that can be used
in the packaging application
Title of paper Polyolefins Reference
Electret-thermal analysis to LDPE/starch blends Ratanakamnuan and Aht-Ong
assess biodegradation of poly- (2006)
mer composites
Effect of compatibilizer on the LDPE/starch blends Thakore et al. (2001)
biodegradation and mechani-
cal properties of high starch
content/low-density polyethyl-
ene blends
Photo biodegradation of low- LDPE/starch blends Roy et al. (2007)
density polyethylene/banana
starch films
Studies on biodegradabil- LDPE/starch blends/starch Garg and Jana (2007)
ity, morphology and thermo phthalate
mechanical properties of
LDPE/modified starch blends
Soil burial of Polyethylene- LDPE/soya powder blends Sam et al. (2011)
g-(Maleic Anhydride)
Compatibilized LLDPE/Soya
powder blends
Thermal degradation of biode- LDPE/cellulose/ Pedroso and Rosa (2005)
gradable blends of polyethylene ethylcellulose
with cellulose and ethylcellulose
Linear low-density LDPE/soya powder blends Sam et al. (2009)
polyethylene/soya powder
blends containing PE-g-MA
copolymer as a compatibilizer
A new approach for morphol- poly(butylene adipate-co- Choi et al. (2006)
ogy control of poly(butylene terephthalate) (PBAT)/soy
adipate-co-terephthalate) and protein concentrate (SPC)
soy protein blends

6.5 Conclusion

The rising ethical awareness and ‘green consumerism’ among the consumers had
leaded the researchers to put more efforts in the development of green products. To
this effect, there has been a rapid increase in the interest in environmental and eth-
ical issues in consumer attitudes. Consumers are playing the important roles in the
environmental problems by recycling and choosing environment friendly products
and ways of life. There are relatively few studies about the impact of environmen-
tal preferences in the actual product or brand choice situations, instead of intention
to buy.
Many consumers fail to admit the connection between their buying decision
and various environmental consequences if there is no environmental infor-
mation, such as labels, to remind them of it. Other reasons include the lack of
6  Current Application and Challenges on Packaging Industry … 181

supply of environment friendly packaging options in the marketplace and con-

sumers’ inability to distinguish between the more and less environment friendly
package alternatives (Bech-Larsen 1996; Thøgersen 1994). As a final conclusion,
the production of green packaging polymers made up by incorporation of natural
polymer into plastic-based petroleum has opened a new chapter in the packaging
industry.

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Chapter 7
Application of Natural Polymers
in Engineering

Amany A. Aboulrous, Tahany Mahmoud, Ahmed M. Alsabagh

and Mahmoud I. Abdou

7.1 Introduction

7.1.1 Role of Natural Polymers in Nonrenewable Energy

(Drilling Muds)

A drilling fluid or muds is used in a drilling process in which the fluid is pumped
from the surface, down the drill string, through the bit, and back to the surface
via the annulus (Fig. 7.1). The drilling fluid or muds is essential to maintain an
effective and productive oil well drilling process. Drilling muds are mainly com-
posed of liquid (i.e., water, brine, or oil) and solid materials (i.e., clay, barite,
polymer, and chemical additives). Unfortunately, drilling fluid’s composition has
become more complex to satisfy the demand and challenges of drilling operations.
The materials used to satisfy these demand can be corrosion inhibitors, weight-
ing agents, lubricants, biocides, detergents, defoamer, emulsifiers, surfactants, lost

A.A. Aboulrous (*) · M.I. Abdou 

Production Department, Egyptian Petroleum Research Institute,
1 Ahmed El-Zomor Street - El Zohour Region, Nasr City 11727, Cairo, Egypt
e-mail: amany.a.aboulrous@gmail.com; amany.aboulrous@yahoo.com
M.I. Abdou
e-mail: mahmoud_ibrahim_abdu@yahoo.com
T. Mahmoud · A.M. Alsabagh 
Petroleum Application Department, Egyptian Petroleum Research Institute,
1 Ahmed El-Zomor Street - El Zohour Region, Nasr City 11727, Cairo, Egypt
e-mail: tahany.mahmoud.a@gmail.com
A.M. Alsabagh
e-mail: alsabaghh@gmail.com

© Springer International Publishing Switzerland 2016 185

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_7
186 A.A. Aboulrous et al.

Fig. 7.1  Drilling fluid circulating system

circulation agents, viscosifiers, shale inhibitors, and others (Darley and Gray 1988;
Fink 2003; United States Government 2015).
Drilling muds perform many tasks during its circulation into the well
(Growcock and Harvey 2005) as shown in Fig. 7.1 such as:
1. Generate, suspend, and remove drill solids (cuttings) from borehole in the
ground.
2. Cool, clean, and lubricate the bit.
3. Maintain the stability of the borehole.
4. Sealing the permeable formations.
5. Control the corrosion.

7.1.1.1 Classification of Drilling Muds

The drilling muds can be divided into five categories as follows:

Gas-Based Drilling Muds
This type of drilling muds is used when special conditions exist (i.e., hard rock-
ing drilling). Compressed dry air, natural gas, mist, or foams can form gas-based
7  Application of Natural Polymers in Engineering 187

drilling muds plus chemical additives (Quintero 2002). There are two major limi-
tations for this type of drilling muds:
A. The possibility of explosion, so it is recommended to use gas detectors while
drilling with gas-based drilling muds.
B. This type was not recirculated and materials were added continuously.
Water-Based Drilling Muds
They were the simplest, oldest, and cheapest type of drilling fluids. They mainly
consist of three components: water (fresh, brine, or saturated salt), clay (bentonite,
kaolinite, or illites), and other chemicals. The type and the quantity of the other
chemicals depend on the local conditions at the well and on the salt concentration.
The primary functions for the clay are to provide the initial viscosity to suspend
the drilling cuttings and decrease the fluid loss by forming film on the formation
of the well. This type is generally nontoxic to the environment and humans (U.S.
Environmental Protection Agency 1993).
Polymer-Based Drilling Muds
Natural polymers are added to inhibit both corrosion and degradation of polymers
by O2, CO2, and H2S and they prevent shale sloughing so it is suitable for drilling
shale well (American Petroleum Institute 2004). They have high shear-thinning
ability at high shear rate
It consists of fresh or sea water, KCl, viscosity building polymer (xanthenes),
CMC or stabilized starch, caustic soda, and lubricants. This type has also high
shear thinning and high true yield strength.
The main advantages of this type are: It supports the bit hydraulics and the bore
hole stability. This type does not cause formation damage due to its low solid con-
tents. It is suitable for drilling at temperature up to 250 °F (121 °C) (Luheng 2014).
Oil-Based Drilling Muds
They consist of oil (i.e., diesel oil, mineral oil, and so on) and minimum quantity
of water if they had higher quantity of water, they would be called invert emulsion
Muds. The water is added in this type of muds to react with the other additives
and enhance the rheological properties. Organophilic clays or colloidal asphalts
were used also to control the rheological and the filtration properties (Rodolfo
and Tailleur 1955). Emulsifiers are used to stabilize the formulation of this kind of
muds (Zuzich and Blytas 1994).
This type of muds has been used to gain good lubricity at high temperature (i.e.,
high angle drilling) where water-based muds may be thermally unstable, for shale for-
mation drilling and to minimize the corrosion (Zuzich et al. 1995; Blytas et al. 1992).
The main disadvantages of this kind of muds are the environmental limitations
and the cost of its formulation (Blytas and Frank 1995).
Synthetic-Based Drilling Muds
Due to the toxicity of the oils used in oil-based drilling fluids, the synthetic-based
drilling muds appears as a substitute for oil-based drilling muds by replacing the
oil by synthetic ones (such as ester and ether) (Munro et al. 1993).
188 A.A. Aboulrous et al.

They have the same desirable properties as these of the oil-based muds so they
were often called pseudo-oil muds. They are considered more expensive than oil-
based muds. This type of muds is useful for deepwater and deviated hole drilling.

7.1.1.2 Drilling Muds Properties

A variety of properties are monitored to satisfy the drilling process and guide for-
mulation and treatment of muds.
Muds Weight (Muds Density)
It is measured by a muds balance and is normally measured in pounds per gallon
(lbm/gal) or (ppg). The muds weight can be increased by the addition of barite,
ilmenite, halite, or calcium carbonate (Abdou and Ahmed 2010).
Filtration
One of the most important functions for the muds is the ability of the muds to
seal the permeable formation by forming thin, low permeable filter cake. There
are two types of materials which enter the formation; the first type is fine particles
which called muds spurt and the second type is liquid which is known as the fil-
trate (Cerasi and Soga 2001).
The model suggests that the filtration rate and the suspended fine particles are
the responsible factors for the formation of the filter cake (Fink 2012; Kabir and
Gamwo 2011) as shown in Fig. 7.2.
The filtration performance is determined using standard API filtration test.
In this test, the cell equipped with filter paper, is full of drilling fluids and then
100 psi pressure is applied to the cell and finally the filtrate volume after 30 min is
calculated (American Petroleum Institute 2009).

Fig. 7.2  The formation of a filter cake in a porous formation from suspension (filled circle) in a
drilling fluid
7  Application of Natural Polymers in Engineering 189

Muds Rheological Properties

The rheological properties played a very important role in determining the success
of the drilling process.
It can be measured by two methods (American Petroleum Institute 2009):
A. Marsh funnel, the funnel is filled by 946 ml of muds and then notes the time
required for the discharge of this amount and the time should be less than
1 min.
B. Fann V-G meter, different parameters (i.e., plastic viscosity, apparent viscosity,
yield point, and gel strength) are measured by taking six reading at 600, 300,
200, 100, 6, 3 rpm.
Plastic Viscosity (PV)
The value of plastic viscosity is derived from two readings from Fann meter (600
and 300 rpm). The low value of plastic viscosity is desirable as the drilling process
is rapid due to the low viscosity of the muds existing at the bit. The high values
indicate the existence of excess solids or viscous base fluid. By dilution, we can
lower the value of plastic viscosity (Negm et al. 2014).
PV (in centipoise) = φ600 − φ300
where φ600 is the reading of the viscometer at speed 600 rpm and φ300 is the
reading of the viscometer at speed 300 rpm.
Apparent Viscosity (AV)
The viscosity of a fluid is measured at a given shear rate at a fixed temperature.
In order for a viscosity measurement to be meaningful, the shear rate must be
stated or defined. It is a rheological property calculated from viscometer readings
performed by a Muds engineer on drilling fluid. It is normally abbreviated as AV
(sometimes denoted η). It is expressed in cP (centipoise). These calculations and
tests help the muds engineer develop and maintain the properties of the drilling
fluid to the specifications required (Rosa et al. 1995).
Yield Point (YP)
The yield point is the resistance of the fluids to initial flow or the stress required
to start fluid movement. The higher value of yield point is desirable as the drilling
muds had the ability to carry cuttings better than fluid with the same density but
with lower yield point (Aboulrous et al. 2013).
 
YP lb/100 ft2 = 2(AV − PV)

where AV is the apparent viscosity measured and PV is the plastic viscosity meas-
ured in centipoise.
The true yield point (Yt) is affected by the concentration of solids, their electri-
cal charge, and surface properties of the muds.
 
Yt lb/100 ft2 = 3/4 YP
190 A.A. Aboulrous et al.

Gel Strength
The gel strength is the measure of the minimum shear stress required to produce
movement of muds. Gel strength played a very important role in suspending cut-
tings. Excessive gel strength can cause many problems as stuck pipes. It is meas-
ured using Fann meter at 3 rpm reading at 10 s and it can be measured also at
10 min (Van Oort et al. 2004).
Muds Additives
Muds Thickeners
Thickener polymers include polyacrylamide, polyesters, polyacrylates, natural poly-
mers, and modified natural polymers (Doolan and Cody 1995). Table 7.1 illustrates
some examples for the thickener polymers that are used in drilling fluids. The main
advantage of polymers is that they cause little change in solid contents of muds.
Muds Filtrating Reducing Agents
There are numerous cellulose-based fluid loss additives which are used to mini-
mize the invasion of drilling fluids through the permeable formations. An apparent
viscosity in water of at least 15 cP is needed to achieve an API fluid loss of less
than 50 ml/30 min (Raines 1986).
A mixture containing polyanionic cellulose (PAC) and a synthetic sulfonate pol-
ymer has been tested to minimize the drilling fluid loss and thermal stability for a
water-based drilling fluid at high well drilling temperatures up to 300 °F (150 °C)
(Hen 1991).
Hydroxyethyl cellulose (HEC) with a degree of substitution of 1.1–1.6 has been
used for fluid loss reduction in water-based drilling fluids (Raines 1986). While
Chang et al. (1998) have used cross-linked HEC for high-permeability formations.

Table 7.1  Thickener polymers
Compound References
Polyethylene glycol Lundan and Lahteenmaki (1996)
Carboxymethyl cellulose Lundan et al. (1993)
Combination of a cellulose ether with clay Rangus et al. (1993)
Amide-modified carboxyl-containing polysaccharide Batelaan and van der Horts (1994)
Copolymers acrylamide–acrylate and Waehner (1990)
vinylsulfonate–vinylamide
Cationic polygalactomannans and anionic xanthan gum Yeh (1995)
Copolymer from vinyl urethanes and AA or alkyl Wilkerson et al. (1995)
acrylates
2-Nitroalkyl ether–modified starch Gotlieb et al. (1996)
Polymer of glucuronic acid Courtois-Sambourg et al. (1993)
Ferrochrome lignosulfonate and carboxymethyl Kotelnikov et al. (1992)
cellulose
Cellulose nanofibrils Langlois (1998), Langlois et al.
(1999)
Chitosan House and Cowan (2001)
7  Application of Natural Polymers in Engineering 191

Fig. 7.3  Starch derivates

The etherified or esterified form of HEC can be used as fluid loss control addi-
tives (Audibert et al. 1997; Chang and Parlar 1999). It was found that a derivatized
HEC polymer gel has little or no damage to the formation permeability (Nguyen
et al. 1996).
Succinoglycan is a natural biopolymer, which can be used as fluid loss control
additive during oil field drilling (Lau 1994). Succinoglycan does not depend on
viscosity to reduce fluid loss. Unfortunately, it can cause formation damage as it
forms easy-to-remove filter cake.
Some cellulosic materials are shown in Fig. 7.3 Mixtures that contain metal
hydroxides and a polysaccharide, partially etherified with hydroxyethyl and
hydroxypropyl groups, are used to reduce fluid loss in water-based drilling fluids
(Plank 1993).
Johnson (1996) has used to minimize the fluid loss a mixture of graded calcium
carbonate particle sizes, a nonionic polysaccharide of the scleroglucan type, and a
modified starch. Gellan has been used as a filtrate reducer in water-based drilling
fluids (Dreveton et al. 1998).

7.1.1.3 Drilling Problems

There are some problems in drilling process which exist due to the wrong values
of muds parameters. These problems can be overcome or minimized by addition
of some materials (Aboulrous et al. 2013).
Some of the problems are:
A. Muds losses during circulation
B. Stuck pipe
C. Corrosion of the drill pipe.

7.1.1.4 Lost Circulation Problem

Lost circulation is leaking of drilling fluids into the well formations. The lost cir-
culation is one of the biggest contributors to drilling nonproductive time and ruins
192 A.A. Aboulrous et al.

the specifications of the drilling process. This problem may lead to complete loss
of the well due to the reduction of the pressure gradient manageable (Aboulrous
et al. 2013).

7.1.1.5 The Classification of Drilling Muds According to Losses

Seepage Loss Muds (SLM)

It is called seepage losses muds when losses are 1–5 bbl/h during drilling pro-
cess. Once it was determined that the fluid was being lost, the operator must
make a decision of whether to tolerate or treat these losses. It might be possible
to continue the drilling if the fluid was cheap and the pressures were manageable
(Aboulrous et al. 2013; Nayberg and Petty 1986).
Partial Loss Muds (PLM)
It is the drilling fluids which lost 5–100 bbl/h (Nayberg and Petty 1986)
Severe Loss Muds (SVLM)
When the drilling fluid loss was more than 100 bbl/h (Nayberg and Petty 1986).
The last two types of muds require immediate treatment for these losses.

7.1.1.6 Types of Loss Circulation Zones

The idea that the pressure of specific zone exceeded the muds weight pressure,
was the dominated reason for the lost circulation until (Gockel et al. 1987) indi-
cated otherwise. They had found four types of formations that were responsible for
the lost circulation (Howard and Scott 1951) (as in Fig. 7.4)

Fig. 7.4  Illustrates four types of formations which are responsible for the lost circulation
7  Application of Natural Polymers in Engineering 193

1. High-permeability unconsolidated gravels where lost circulation caused a cav-

ity. This type of loss can be controlled by muds weight.
2. Low-pressurized cavernous or vugular zones which are found in carbonate or
volcanic formations due to two reasons:
A. Continuous water flow through the dissolved parts of the rock in limestone.
B. The cooling of magma.
3. Natural fractures or fissures, faults, and transition zones in carbonate.
4. Induced fractures due to the extensive hydraulic pressures.

7.1.1.7 Loss Circulation Treatment

Rojas et al. (1998) demonstrated six ways for controlling the muds losses during
drilling which can be done through the planning and execution of the well.
Drill String Geometry and Casing Design
The equivalent circulating density depends on casing design, drill string geome-
try, and hole size. These parameters should be taken in operator’s mind during the
planning stage. It is advisable to use bicentered bits to reduce the equivalent circu-
lating density and select casing seats to minimize the exposure time of loss zones.
Muds Rheology
The muds rheology and flow rate should satisfy all drilling functions such as hole
cleaning and cuttings removal as well as minimizing the equivalent circulating
density.
Muds Weight Selection
In practice, we cannot reduce the equivalent circulating density by lowering the
muds weight due to the increasing possibility of wellbore collapse.
Sealing Properties of Drilling Muds
The size of the solids, which exist in the drilling muds, control losses to high-per-
meability formation and small fractures as they function as bridging materials.
Hole Cleaning Efficiency
Failure to transport cuttings would result in cuttings accumulation in the annulus
which led to higher frictional pressure drops in the well and higher equivalent cir-
culating densities.
Lost Circulation Control Materials (LCM)
There are a variety of lost circulation additives shown in Table 7.2 but the poly-
meric materials have the largest impact in the reduction of fluid loss during drill-
ing due to their viscosity as superabsorbent materials (Fink 2003; Alsabagh et al.
2013).
Lost circulation materials were evaluated using permeability plugging appara-
tus using the ceramic disks with different pore throat diameters as a filter medium
at differential pressures to simulate the conditions of the well. The filtration
194 A.A. Aboulrous et al.

Table 7.2  Lost circulation additives

Material References
Encapsulated lime Walker (1986)
Encapsulated oil-absorbent polymers Delhommer and Walker (1987)
Hydrolyzed polyacrylonitrile Yakovlev and Konovalov (1987)
Poly(galactomannan) gum Kohn (1988)
Partially hydrolyzed polyacrylamide 30 % hydrolyzed, Sydansk (1990)
cross-linked with Cr3+
Oat hulls House et al. (1991)
Rice products Burts (1992, 1997)
Waste olive pulp Duhon (1998)
Nut cork Fuh et al. (1993), Rose (1996)
Pulp residue waste Gullett and Head (1993)
Petroleum coke Whitfill et al. (1990)
Shredded cellophane Burts (2001)

parameters can be made from the data collected at 7.5 and 30 min intervals
according to the following formulas (American Petroleum Institute 2009):
PPT = 2 × V30 min
  
SL = 2 × V7.5 min − V30 min − V7.5 min
 
SFR = 2 × V30 min − V7.5 min /2.739

where PPT is the permeability plugging tester value(ml); V30 min (ml) is the total

filtrate collected in 30 min; SL is the spurt loss (ml); V7.5 min (ml) is the filtrate
collected in 7.5 min; and SFR is the static filtration rate (ml/min1/2).

7.1.1.8 Water-Soluble Natural Polymers as Lost Circulation Control

Materials (LCM)

Cellulosic natural polymers (i.e., carboxymethyl cellulose, guar gum, and starch)
are available in abundance so they are low cost. The carboxymethyl cellulose
(CMC) is a cellulose derivative with carboxymethyl groups (ACH2ACOOH)
bound to some of the hydroxyl groups of the glucopyranose units that form the
main backbone of cellulose. The guar gum is a polysaccharide that contained
the sugars galactose and mannose. The backbone of gum is a linear chain of
1,4-linked mannose units to which galactose units are 1,6-linked at every second
mannose, forming short side branches. Starch is composed of anhydroglucose
units having 1, 4-linkages (Fink 2003; Alsabagh et al. 2014).
Filtration Parameters for Natural Polymers
From Tables 7.3, 7.4, and 7.5, by changing the ceramic disks (60 and 90 μ) at
100 and 300 differential pressures, the CMC exhibited the best performance in
Table 7.3  Filtration parameters for carboxymethyl cellulose (CMC) using different ceramic disks at different pressures
Conc. % V7.5 min (ml) V30 min (ml) PPT value (ml) Spurt loss (ml) Static filtration rate Filter cake (mm)
(ml/min1/2)
100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi
At 60 μ ceramic disks
0.1 20.2 22 23.8 26.5 40.1 44 33.2 35 2.6 3.3 0.17 0.12
0.3 30.8 35.2 34.9 41 61.6 70.4 53.4 58.8 2.9 4.2 0.19 0.15
7  Application of Natural Polymers in Engineering

0.6 43.9 50.2 50 57 87.8 100.4 75.6 86.8 4.5 4.9 0.2 0.17
At 90 μ ceramic disks
0.1 23.7 27.2 28 32 47.4 54.4 38.8 44.8 3.1 3.5 0.17 0.12
0.3 42.6 48.4 48 54.5 85.2 96.8 74.4 84.6 3.9 4.5 0.19 0.15
0.6 51 58.3 58 65.6 102 116.6 88 102 5.1 5.3 0.2 0.17
195
 196

Table 7.4  Filtration parameters for guar gum (MG) using different ceramic disks at different pressures
Conc. % V7.5 min (ml) V30 min (ml) PPT value (ml) Spurt loss (ml) Static filtration rate Filter cake (mm)
(ml/min1/2)
100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi
At 60 μ ceramic disks
0.1 32.7 37.8 36.6 42.7 73.2 85.4 57.6 65.8 2.8 3.6 0.25 0.21
0.3 21.3 23.8 24.8 28.2 49.6 56.4 35.6 38.6 2.5 3.3 0.27 0.25
0.6 46.4 53.3 51.4 58.5 102.8 117 82.8 96.2 3.7 4 0.3 0.27
At 90 μ ceramic disks
0.1 43.6 51.2 47.7 56.3 95.4 112.6 79 92.2 3 3.5 0.25 0.21
0.3 25.1 29.3 28.9 34.1 57.8 68.2 42.6 49 2.7 3.5 0.27 0.25
0.6 54 62.3 59.2 67.8 118.4 135.6 97.6 113.6 3.8 4.1 0.3 0.27
A.A. Aboulrous et al.
Table 7.5  Filtration parameters for potato starch (MS) using different ceramic disks at different pressures
Conc. % V7.5 min (ml) V30 min (ml) PPT value (ml) Spurt loss (ml) Static filtration rate Filter cake
(ml/min1/2) thickness (mm)
100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi 100 psi 300 psi
At 60 μ ceramic disks
0.1 33.8 42.5 37.3 47.7 74.6 95.4 59.4 74.6 3 3.8 0.18 0.16
0.3 30 40.2 34.8 45.5 69.6 91 50.4 69.8 3.5 3.9 0.26 0.2
7  Application of Natural Polymers in Engineering

0.6 23.5 32 27 36 54 72 40 56 2.6 2.9 0.26 0.23

At 90 μ ceramic disks
0.1 43.6 51.2 47.7 56.3 95.4 112.6 79 92.2 3 3.5 0.2 0.18
0.3 37.1 47.2 42 53 84 106 64.4 82.8 3.6 4.2 0.24 0.18
0.6 32.7 37.8 36.6 42.7 73.2 85.4 57.6 65.8 2.8 3.6 0.23 0.2
197
198 A.A. Aboulrous et al.

all the filtration parameters such as filtrate volume after 30 min, PPT value, spurt
loss, and static filtration at 0.1 % concentration. While the maximum efficiency
for the guar gum and potato starch is pronounced at 0.3 and 0.6 %, respectively
(Alsabagh et al. 2014).
The filtrate loss after 30 min (ml) was 16.7, 18, and 24.2 against the CMC, guar
gum, and potato starch, respectively. On the other hand the spurt loss decreased
from 35.6, 24, and 22.6 ml against the potato starch, guar gum, and CMC, respec-
tively. By investigating the results of permeability plugging tester value, it was
found that the CMC pronounced the best results among the guar gum and potato
starch. The same result was exhibited by examining the static filtration rate values
with the same ranking. By analyzing the filter cake data, it was found that the fil-
ter cake for CMC is more elastic and without any bubbles (ranging from 0.12 to
0.2 mm) among the coming results by the guar gum and the potato starch (rang-
ing from 0.17 to 0.3 mm) and their filter cakes having instability and bubbles
(Alsabagh et al. 2014).
The obtained good results by the CMC in the filtration parameters may be due
to the CMC having surface active properties and forming micellar solution so that
the micelles may form an external filter cake which leads to complete plugging of
the pores to prevent the filtration loss (Alsabagh et al. 2014) as shown in Fig. 7.5.
Surface Tension Parameters for Natural Polymers
From Table 7.6 the CMC forms critical micelle concentration formation (CMCF).
These data mean that it has surface active properties. Meanwhile the guar gum and
the potato starch have cleared undistinguished CMCF. These results illustrated the
reason that the CMC exhibited good results among the guar gum and the potato
starch. The ΔGads (−4.1) of the CMC in Table 7.6 means that its adsorbability on
the surface of the rocks leads to maximum stability for the formed filter cake layer
(Alsabagh et al. 2014).

7.1.1.9 Water-Insoluble Natural Polymers as Lost Circulation

Materials

Three natural water-insoluble cellulosic materials were investigated as lost circula-

tion control material depending on their physical and chemical properties (particle
size distribution and chemical composition).
Effect of Particle Size Distribution of Natural Materials on Filtration
Parameters
All fine-sized materials have the best results in filtration volume, PPT value, and
spurt loss and that is because the fine-sized material gives better filling properties.
A bridge may be initiated when several particles of lost circulation material lodge
against each other in the pore throat. The smaller particles may then bridge the
openings between the larger, previously bridged particles. This process continues
until the pore plugged. The fine-sized materials have more surface area so they
possess more resistance to pressure and they can plug pore (Alsabagh et al. 2016).
7  Application of Natural Polymers in Engineering 199

Fig. 7.5  Shows the mechanism of CMC as lost circulation control materials through micelle for-
mation. Adapted from Alsabagh et al. (2014)

Table 7.6  Thermodynamic parameters for natural water-soluble polymers at 25 °C

Material γ CMC Γmax × 10−10 Amin × 102 πCMC ΔGmic ΔGads
CMC 55 0.42 4.2 17.3 +0.55 −4.1
Guar gum NA 0.48 3.4 NA NA NA
Starch NA NA NA NA NA NA
200 A.A. Aboulrous et al.

Effect of Concentration of Natural Polymers on Filtration Parameters

From Fig. 7.6a–c, it can be concluded that if the concentration of the three inves-
tigated cellulosic materials increases (at concentration 0.6 %), the filtration per-
formance will be better in all filtration parameters (Alsabagh et al. 2016). These
results meet with what Abram in 1977 stated; high concentration provides better
sealing.
This concentration is considered to be optimum as it is the best concentration
with changing the applied differential pressure and the permeability of ceramic
disks.

Fig. 7.6  Illustrates the filtration parameters for peanut hulls, bagasse, and sawdust (in fine size)
with 90 μ ceramic disks at 100 psi where a filtrate volume (vs.) concentration. b PPT value (vs.)
concentration. c spurt loss (vs.) concentration. Adapted from Alsabagh et al. (2016)
7  Application of Natural Polymers in Engineering 201

Table 7.7  The composite of the investigated water-insoluble natural polymers

Materials Cellulose (%) Crude fiber (%) Water (%) Ash (%) Lignin (%) Other (%)
Peanut hulls 25 60 8 2 – 5
Bagasse 55 – 5 4 24 12
Sawdust 58.2 – 4.8 0.21 28.4 5.1

Effect of Cellulosic Content of Natural Material on Filtration Parameters

All filtration parameters enhanced with all investigated materials and all inves-
tigated materials decrease the flow rate of the water-based muds drastically. The
peanut hulls show the better performance in reducing the loss circulation of drill-
ing fluids than the bagasse and sawdust as shown in Fig. 7.6a–c. These results may
be because the peanut hulls contain crude fiber (60 %) and the least content of cel-
lulose (25 %) and the sawdust is the worst one because it has the highest content
of cellulose (58.2 %) (Alsabagh et al. 2016) as shown in Table 7.7 and that makes
it more friable under pressure.

7.1.1.10 Scanning Electron Microscope (SEM) for the Formed Internal

Filter Cakes

The ceramic disks have been photographed by SEM to investigate the plugging
quantity of investigated materials. Best filtration result of 60 μ ceramic disk is
shown in Fig. 7.7a–c (Alsabagh et al. 2016).

7.1.2 Role of Natural Polymers in Renewable Energy

(Biomass)

The world currently depends heavily on coal, oil, and natural gas for its energy.
Fossil fuels are nonrenewable as they draw on finite resources that will eventu-
ally dwindle. This type of energy is becoming too expensive, too environmen-
tally damaging and the reason for global warming. In contrast, the many types of
renewable energy resources such as wind, solar energy, and biomass are constantly
replenished and will never run out (McKendry 2002).
According to Renewable Energy Policy Network for the 21st Century (2010,
2011, 2012) renewables contributed 19 % to our energy consumption and 22 %
to our electricity generation in 2012 and 2013, respectively; while it contributes
16.7 % to our energy consumption during 2010 as shown in Fig. 7.8. For both
modern renewables, such as hydro, wind, solar, and biofuels, and traditional bio-
mass, worldwide investments in renewable technologies amounted to more than
US$214 billion in 2013. Figure 7.9 shows global growth of renewables throughout
2011.
202 A.A. Aboulrous et al.

Fig. 7.7  Represents 60 μ ceramic disk a before PPT, b after PPT (6 % of fine-sized peanut
hulls), c after PPT (6 % of fine-sized sawdust). Adapted from Alsabagh et al. (2016)

Fig. 7.8  Total world energy consumption by 2010. Adapted from Renewable Energy Policy Net-
work for the 21st Century (2010)
7  Application of Natural Polymers in Engineering 203

Fig. 7.9  Global growth of
renewables throughout 2011.
Adapted from Renewable
Energy Policy Network for
the 21st Century (2011)

7.1.3 Types of Renewable Energy

There are so many kinds of renewable energy (Renewable Energy Policy Network
for the 21st Century 2010) such as
• Electricity generation. Renewable energy provides 21.7 % of electricity gen-
eration worldwide in 2013 (British Petroleum Company 2014). Renewable
power generators are spread across many countries, and the percent for usage
of wind to produce electricity in some areas is, for example, 14 % in the U.S.
state of Iowa, 40 % in the northern German state of Schleswig-Holstein, and
49 % in Denmark (Renewable Energy Policy Network for the 21st Century
2010).
• Transport fuels. Biofuels have contributed to a significant decline in oil con-
sumption in the United States since 2006 (Renewable Energy Policy Network
for the 21st Century 2010). The 93 billion liters of biofuels produced world-
wide in 2009 displaced 68 billion liters of gasoline, equal to about 5 % of world
gasoline production (Renewable Energy Policy Network for the 21st Century
2010).
• Solar energy. Solar hot water makes an important contribution to renew-
able heat in many countries, most notably in China, which now has 70 % of
the global total. Direct geothermal for heating is growing rapidly (Renewable
Energy Policy Network for the 21st Century 2010).
• Biomass. In Sweden, national use of biomass energy has surpassed oil. The use
of biomass for heating continues to grow as well.
204 A.A. Aboulrous et al.

7.1.3.1 Biomass

The use of biomass as renewable energy source is becoming increasingly neces-

sary, if we are to achieve the changes required to address the impacts of global
warming. Biomass is the most common form of renewable energy, widely used in
the third world until recently.
Biomass is considered natural, renewable, and high molecular weight material
which can produce energy. The renewable energy is used mostly to generate electricity
but it can be used also to create alternative fuel (biofuel). Biomass denotes living and
recently dead biological materials which can be used as fuel (Ellabban et al. 2014).
The building blocks of the biomass are the carbohydrates which produce from
the photosynthesis of the plant materials between carbon dioxide (CO2) in the air,
water, and sunlight. The solar energy which is stored in the chemical bonds of car-
bohydrate can be extracted chemically or biologically.
Oxygen is extra product of the extraction process which oxidized carbon to pro-
duce carbon dioxide (CO2) and water. This process is cyclical as carbon dioxide can
produce new biomass. The chemical and physical properties of the high molecular
weight materials determine the value of a particular type of biomass. Biomass is more
secure source for energy as biomass is available in most countries (McKendry 2002).
Many crops are being tested for commercial energy forming. Energy crops
include woody crops, grasses, starch, sugar, and oil seeds. These include also pop-
lar trees and Miscanthus giganteus. The premier energy crop is sugarcane, which
is a source of the readily fermentable sucrose and the lignocellulosic by-prod-
uct bagasse (ADAS 1992). The desired characteristics for the energy crops are:
1. Low cost
2. Low nutrient requirement
3. Low energy requirement to produce
4. High yield (maximum production of dry materials per hectare)
Biomass can be converted into three main types of products.

7.1.3.2 Electrical/Heat Energy

In the UK, the government tries to generate 10 % of the national electricity sup-
ply of 60 GW/year from renewable sources especially biomass (Price 1998; U.S.
Energy Information Administration 2012). It has been reported that electricity can
be produced when microbial foods, such as glucose and acetate, or even organic
compounds in wastewater are fed to the bacteria. Figure 7.10 shows the top five
countries generating electricity from biomass.

7.1.3.3 Transport Fuel (Biofuel)

Since the middle of the twentieth century, the interest of biomass as a precursor
to liquid fuels has increased. The fermentation of lignocellulosic biomass to ethanol
7  Application of Natural Polymers in Engineering 205

Fig. 7.10  The top five countries generating electricity from biomass. Adapted from U.S. Energy
Information Administration (2012)

(Allen and Bennetto 1993) is an essential supply to fuels instead of the fossil fuels.
This process produces no net carbon dioxide in the earth’s atmosphere. There
are so many other lignocellulose-derived fuels such as butanol, dimethylfuran,
and gamma-Valerolactone (Mecheri et al. 2011; Logan 2004).
Among biological fuel cells, enzymatic fuel cells (EFCs) have attracted inter-
est in the last decade due to their use as power sources for portable electron-
ics, and implantable medical devices (Minteer et al. 2007; Barton et al. 2004;
Moehlenbrock and Minteer 2008). Enzymes possess merits over chemical cata-
lysts, such as biocompatibility and biodegradability. By encapsulation technique,
it is possible to entrap the biomolecule in the polymeric matrix while retaining
sufficient mobility. This immobilization procedure depends on the entrapment of
the enzyme in polymer networks without any covalent associations. Several poly-
mer networks have been proposed, among which the use of natural polymers has
been found to provide good environment for enzyme immobilization (Moore et al.
2004; Thomas et al. 2003; Klotzbach et al. 2006).
Glucose oxidase (GOx) is the most widely used enzyme in the field of biosen-
sors due to its high stability and specificity (Wilson and Turner 1992; Tsai et al.
2005). Based on research advances leading to commercially available biosensors,
materials and strategies to design GOx-based biofuel cell have been explored
(Ivnitski et al. 2006).
The hybrid fuel cell combines some features of solar cells, fuel cells, and redox
flow batteries which convert biomass to electricity with the help of a catalyst acti-
vated by solar or thermal energy at low temperature. The hybrid fuel cell can be
any type of biomass sources, including starch, cellulose, lignin—and switch grass,
powdered wood, algae, and waste.
206 A.A. Aboulrous et al.

Fig. 7.11  Shows the hybrid fuel cell

In this hybride fuel cell, the biomass is ground up and mixed with a polyoxo-
metalate (POM) catalyst in solution and then exposed to light from the sun—or
heat. The fuel cell uses polyoxometalates as the photocatalyst and charge carrier
to generate electricity at low temperature. POM oxidizes the biomass under photo
or thermal irradiation, and delivers the charges from the biomass to the fuel cell’s
anode. The electrons are then transported to the cathode, where they are finally
oxidized by oxygen through an external circuit to produce electricity as shown in
Fig. 7.11. This type of cell is not sensitive to impurities unlike the other cell tech-
nologies as it has reported that it is inert to organic and inorganic impurities pre-
sent in the fuels (Sapra 2014).

7.1.3.4 Chemical Feedstock

Lignocellulosic biomass is the feedstock for the pulp and paper industry. This
industry focuses on the separation of the lignin and cellulosic fractions of the bio-
mass. The biomass can be converted to raw materials for polymer synthesis and
modification.
This can be done by liquefaction which is a widely known technology to con-
vert gaseous and solid products to liquids. This technique can even produce novel
thermoset nanocomposites.

7.1.3.5 Lignocellulosic Biomass

Lignocellulosic biomass is the most abundantly available raw material on

the earth for the production of biofuels.
Lignocellulose refers to plant dry matter of higher plants, softwood or hard-
wood. It is composed mainly of carbohydrate polymers (cellulose, hemicellulose),
and an aromatic polymer (lignin). Cellulose provides mechanical strength and
chemical stability to plants. Solar energy is stored in the form of cellulose during
the photosynthesis process. Hemicellulose is a copolymer of different sugar mono-
mers (six and five carbon sugars) which are tightly bound to lignin and also exist
in the plant cell. Lignin is polymer of aromatic compounds that produce reinforce-
ment to the plant walls. It has been reported that about 7.5 × 1010 tons of cellulose
are consumed every year (Kirk-Othmer 2001).
7  Application of Natural Polymers in Engineering 207

There are two main types of linkages identified in the lignocellulose complex.
The main types of bonds that provide linkages within the individual components
of lignocellulose (intrapolymer linkages), and connect the different components to
form the complex (interpolymer linkages). The position and bonding function of
the latter linkages is summarized in Table 7.8 (Faulon et al. 1994).
The content of cellulose, hemicellulose, and lignin in the lignocellulosic bio-
mass highly depends on its source, whether it is wood, softwood, or grasses (Sun
and Cheng 2002) as shown in Table 7.9.

Table 7.8  Overview of linkages between the monomer units that form the individual polymers
lignin, cellulose, and hemicellulose, and between the polymers to form lignocellulose
Bonds within different components (intrapolymer linkages)
Ether bond Lignin, (hemi)cellulose
Carbon to carbon Lignin
Hydrogen bond Cellulose
Ester bond Hemicellulose
Bonds connecting different components (interpolymer linkages)
Ether bond Cellulose–lignin
Hemicellulose–lignin
Ester bond Hemicellulose–lignin
Hydrogen bond Cellulose–hemicellulose
Hemicellulose–lignin
Cellulose–lignin
Adapted from Faulon et al. (1994)

Table 7.9  Composition of lignocellulose in several sources on dry matter

Lignocellulosic materials Cellulose (%) Hemicellulose (%) Lignin (%)
Hardwoods stems 40–55 24–40 18–25
Softwood stems 45–50 25–35 25–35
Nut shells 25–30 25–30 30–40
Corn cobs 45 35 15
Grasses 25–40 35–50 10–30
Paper 85–99 0 0–15
Wheat straw 30 50 15
Sorted refuse 60 20 20
Leaves 15–20 80–85 0
Cotton seed hairs 80–95 5–20 0
Newspaper 40–55 25–40 18–30
Waste papers from chemical pulps 60–70 10–20 5–10
Primary wastewater solids 8–15 NA 24–29
Swine waste 6 28 NA
Solid cattle manure 1.6–4.7 1.4–3.3 2.7–5.7
Coastal Bermuda grass 25 35.7 6.4
Switchgrass 45 31.4 12
208 A.A. Aboulrous et al.

Lignocellulosic biomass can be classified into virgin biomass, waste biomass,

and energy crops. Virgin biomass is all naturally occurring plants such as trees,
bushes, and grass. Waste biomass is produced as a low-value by-product of various
industries such as agriculture. Energy crops are crops with high yield of dry mat-
ters (lignocellulosic biomass) produced to be used in production of energy such as
switch grass (Panicum virgatum) and elephant grass (Carioca et al. 1985).

7.1.4 Other Applications of Natural Polymers

in Engineering

Significant volumes of wastewaters, with organic and inorganic contaminants such

as suspended solids, dyes, pesticides, toxicants, and heavy metals, are discharged
from various industries. These wastewaters create a serious environmental prob-
lem and pose a threat to water quality when discharged into rivers and lakes (Lee
et al. 2014). Thus, such contaminants must be effectively removed to meet increas-
ingly stringent environmental quality standards. It is increasingly recognized that
the nontoxic and biodegradable biopolymer chitosan can be used in wastewater
treatment (Peniston and Johnson 1970).
The need for the environmentally friendly materials in treating water and
wastewater continue to increase during last decade so bioflocculants have emerged
to replace conventional commercial ones. Polysaccharides or natural polymers
may be of great interest because they are natural polymers, environmentally
friendly materials (biodegradable polymers), and easily available from agricultural
resources (Bolto and Gregory 2007). They are not used only in food and fermenta-
tion processes, pharmaceutical, cosmetic, downstream processing but also in water
and wastewater treatment.

7.1.4.1 Mechanism for Natural Bioflocculants

For example, the chitosan behaves as cationic bioflocculant (reactive amino and
hydroxyl groups) and have high molecular weight, so it can treat wastewater by
both mechanisms, coagulation by charge neutralization and flocculation by bridg-
ing mechanism (Li et al. 2013) as shown in Fig. 7.12. In a study that reported coag-
ulation and flocculation of dye-containing solutions using the chitosan, the anionic
dye was electrostatically attracted by protonated amine groups from chitosan and
then neutralizes the anionic charges of dyes and finally the agglomerates settle
down by the flocculation which was enhanced by the bridging mechanism (Guibal
and Roussy 2007). The behavior of chitosan involves two factors, hydrophobic
interactions and the formation of hydrogen bonds. Anionic bioflocculants (cellu-
lose, tannin, and sodium alginate) cannot flocculate anionic contaminants from the
wastewater without the assistance to neutralize the negatively charged impurities,
so we must add inorganic metal salts (e.g., aluminum and ferric salts) or cationic
7  Application of Natural Polymers in Engineering 209

Fig. 7.12  Schematic view
of a flocculation mechanism.
Adapted from Dobias and
Stechemesser (2005)

polymer (e.g., chitosan) (Khiari et al. 2010; Özacar and Şengıl 2003; Roussy et al.
2005; Suopajärvi et al. 2013; Wu et al. 2012; Dobias and Stechemesser 2005). For
many years, bioflocculants such as chitosan, tannins, cellulose, alginate, gums, and
mucilage have been attracting wide interest for treating the wastewater.

7.1.4.2 Chitosan

Cationic biopolymers or polyelectrolytes are of increasing interest as flocculants

in wastewater. Chitosan is a valuable polymeric waste produced from the shells
of crustaceans. Crab shells consist of chitin, protein/caroteins, chitin, and calcium
carbonate (Peniston and Johnson 1970). Prawn, lobster, and crab shells are a par-
ticularly rich source of this chemical, containing 15–20 % of chitin (the chitosan
source). Chitin is a polymer of the polysaccharide class, a cellulose-like biopolymer
containing mainly of β-(1→4)-2 acetamido-2-deoxy-d-glucose units. The struc-
ture of chitin is shown in Fig. 7.13. The main components of chitins are shown in
Fig. 7.14. Chitosan is a partially deacetylated polymer obtained from the alkaline
deacetylation of chitin. It is a linear hydrophilic amino-polysaccharide with a rigid
structure containing both glucosamine and acetylglucosamine units. The structure
of chitosan is shown in Fig. 7.15. Chitin has been found in a wide range of natu-
ral sources, such as crustaceans, fungi, insects, annelids, mollusks, etc. The world’s
market for seafood crustaceans, particularly prawns, shrimp, crab, crayfish, and lob-
ster, is several million tons per year, of which 50 % is discarded as shell waste.

Fig. 7.13  Structure of Chitin
210 A.A. Aboulrous et al.

Fig. 7.14  Percentage of
chitin from different sources

Fig. 7.15  Structure of
Chitosan

The shells contain significant amounts of calcium carbonate and the polymer chitin
(15–20 % w/w), which can be N-deacetylated, using concentrated sodium hydrox-
ide to produce the polysaccharide chitosan. Actually, chitin is the world’s second
most abundant naturally occurring polysaccharide. In fact, these biopolymers are
considered to be a key material in the external protective structure of living systems,
so chitin and chitosan have several outstanding properties (Gerente et al. 2007).
To facilitate electrostatic interactions between polymer chains and the nega-
tively charged impurities in wastewater, we should dissolve chitosan in acids to
produce protonated amine groups along the biopolymer chains (Renault et al.
2009; Muzzarelli 1977).
Numerous works have reported its promising coagulation and flocculation
properties for dye molecules in dye-containing solutions (Guibal and Roussy
2007) or organic matter (e.g., lignin and chlorinated compounds) in pulp and paper
mill wastewater (Rodrigues et al. 2008), heavy metals and phenolic compounds in
cardboard-mill wastewater (Renault et al. 2009), and inorganic suspensions in kao-
linite suspension (Li et al. 2013).

7.1.4.3 Tannin

Tannin is an anionic biopolymer (Özacar and Şengıl 2000) which extracts from
vegetal secondary metabolites such as bark, fruits, leaves, and others (Beltrán
7  Application of Natural Polymers in Engineering 211

Heredia and Sánchez Martín 2009). It has been tested in removal of colloi-
dal impurities in drinking water treatment (Özacar and Şengıl 2003), removal of
suspended matters from synthetic raw water (Özacar and Şengıl 2000), and
removal of dyes, pigments, and inks from ink containing wastewater (Roussy et al.
2005). Some studies showed that the coagulant such as aluminum sulfate with the
negatively charged colloidal particles estabilized with anionic tannin acted as floc-
culant to bridge the aggregates together to settle the flocs. In order to eliminate
the need for the coagulant, modified tannin (Tanfloc flocculant) has been investi-
gated recently to remove heavy metals from polluted water (Beltrán Heredia and
Sánchez Martín 2009) and in wastewater treatment (Beltrán Heredia and Sánchez
Martín 2009).

7.1.4.4 Gums and Mucilage

In recent years, bioflocculants based on gums and mucilage extracted (as illus-
trated in Fig. 7.16) from plant species that include Hibiscus/Abelmoschus escu-
lentus (Okra), Malva sylvestris (Mallow), Plantago psyllium (Psyllium), Plantago
ovata (Isabgol), Tamarindus indica (Tamarind), and Trigonella foenum-graecum
(Fenugreek) have been examined.
These biopolymers have shown excellent results in treatment of landfill lea-
chate (Al-Hamadani et al. 2011), biologically treated effluent (Anastasakis et al.
2009), textile wastewater (Mishra and Bajpai 2005), tannery effluent (Lee et al.
2014; Mishra et al. 2004), and sewage effluent (Mishra et al. 2003). At least
85 % of total suspended solids (TSS) removal, 70 % of turbidity removal, 60 %
of chemical oxygen demand (COD) reduction, and 90 % of color removal have
been established in these studies. Some of them were effective in low concentra-
tions compared to chemical ones. More than 85 % removal of suspended solids
from sewage wastewater and tannery effluent was achieved using 0.12 mg/L of
okra gum and 0.08 mg/L Fenugreek mucilage, respectively (Mishra et al. 2004;
Agarwal et al. 2001).

7.1.4.5 Cellulose

Cellulose is one of the most abundant natural polysaccharide (Das et al. 2012).
Anionic sodium carboxymethylcellulose (Na-CMC) was tested as environmen-
tally friendly flocculants with addition of aluminum sulfate as coagulant for the
removal of turbidity in drinking water treatment (Khiari et al. 2010). Sodium car-
boxymethylcellulose (Na-CMC) can be extracted from an agricultural waste date
palm rachis. In another study, anionized dicarboxylic acid nanocellulose (DCC)
flocculant showed promising results with addition of ferric sulfate as coagulant in
treating the wastewater (Suopajärvi et al. 2013).
212 A.A. Aboulrous et al.

Fig. 7.16  General processing
steps in preparation of plant-
based flocculants

7.2 Conclusion

Natural polymers play a significant and important role in production of oil and gas
(drilling fluid). They are not only a type of drilling fluids which support a condu-
cive environment for carrying out effective drilling operations but also enhance the
different properties of drilling fluids by adding them as viscosifier, filtrate reducing
agent, or lost circulation control agent. Besides their role in nonrenewable energy,
they also produce biomass especially lignocellulosic biomass to support the renewa-
ble energy. Biomass can be converted into three main types of products; Electrical/
heat energy, Transport fuel (biofuel), and chemical feedstock. They contribute to
the new hybrid fuel cell which combines some features of solar cells, fuel cells, and
redox flow batteries which convert biomass to electricity with the help of a catalyst
activated by solar or thermal energy at low temperature. Their applications in other
fields of engineering are infinite but in this chapter, we show their application in
wastewater treatment. The need for the environmentally friendly materials in treat-
ing water and wastewater continue to increase during last decade so bioflocculants
7  Application of Natural Polymers in Engineering 213

have emerged to replace commercial ones. High molecular weight bioflocculant

can treat wastewater by both mechanisms, coagulation by charge neutralization and
flocculation by bridging mechanism. Chitosan, tannin, gums, mucilage, and cellu-
lose are considered to be the most important examples for bioflocculant.
Acknowledgments  The authors would like to acknowledge all staffs of Egyptian Petroleum
Research Institute for encouragement and support.

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Chapter 8
Cosmetics and Personal Care Products

Géraldine Savary, Michel Grisel and Céline Picard

8.1 Introduction

For many years, manufacture, labelling and supply of cosmetic products are being
submitted to Regulations, depending on the area (European Union, U.S., Canada,
Brazil, Japan, China, etc.). Definition of cosmetics and personal care prod-
ucts therefore varies depending on the countries or world regions. Following the
Regulation (EC) N°1223/2009 of the European parliament and of the council of
30th November 2009, cosmetic products in Europe means “any substance or mix-
ture intended to be placed in contact with the external parts of the human body (epi-
dermis, hair system, nails, lips and external genital organs) or with the teeth and the
mucous membranes of the oral cavity with a view exclusively or mainly to cleaning
them, perfuming them, changing their appearance, protecting them, keeping them in
good condition or correcting body odours”. The term ‘substance’ means a chemical
element and its compounds in the natural state or obtained by any manufacturing
process, including any additive necessary to preserve its stability and any impu-
rity deriving from the process used but excluding any solvent which may be sepa-
rated without affecting the stability of the substance or changing its composition
(Cosmetic Products 2013; Official Journal of the European Union 2009).

G. Savary (*) · M. Grisel · C. Picard 

URCOM, EA 3221, FR CNRS 3038, Université Du Havre,
25, rue Philippe Lebon CS 80540, 76058 Le Havre Cedex, France
e-mail: geraldine.savary@univ-lehavre.fr
M. Grisel
e-mail: michel.grisel@univ-lehavre.fr
C. Picard
e-mail: celine.picard@univ-lehavre.fr

© Springer International Publishing Switzerland 2016 219

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_8
220 G. Savary et al.

In the U.S., The Food and Drug Administration (FDA) Act regulates cosmetics
and defines them as “articles intended to be rubbed, poured, sprinkled, or sprayed
on, introduced into, or otherwise applied to the human body… for cleansing, beau-
tifying, promoting attractiveness, or altering the appearance” [FD&C Act, sec.
201(i)].
Among the important differences between requirements for cosmetics in the
United States and various other countries are the legal definitions of drugs and
cosmetics, restrictions on the use of colour additives and other ingredients, and
registration requirements. Some products regulated as cosmetics in Europe, for
instance, are regulated as drugs in the United States. Sunscreens are a case in
point. There are also differences regarding prohibited and restricted ingredients,
particularly colour additives and preservatives. Some countries may require cos-
metic companies to register their establishments and list products and ingredients
with the government; in the United States, cosmetic registration is highly recom-
mended but remains voluntary (Cosmetics and U.S. Law 2005).
Taking these definitions all together, cosmetic products may include creams,
emulsions, lotions, gels and oils for the skin, face masks, tinted bases (liquids,
pastes, powders), make-up powders, after-bath powders, hygienic powders, toi-
let soaps, deodorant soaps, perfumes, toilet waters and eau de Cologne, bath and
shower preparations (salts, foams, oils, gels), depilatories, deodorants and anti-
perspirants, hair colourants, products for waving, straightening and fixing hair,
hair-setting products, hair-cleansing products (lotions, powders, shampoos), hair-
conditioning products (lotions, creams, oils), hairdressing products (lotions, lac-
quers, brilliantine’s), shaving products (creams, foams, lotions), make-up and
products removing make-up, products intended for application to the lips, prod-
ucts for care of teeth and the mouth, products for nail care and make-up, products
for external intimate hygiene, sunbathing products, products for tanning without
sun, skin-whitening products and anti-wrinkle products, as well as any material
intended for use as a component of a cosmetic product (Official Journal of the
European Union 2009; Cosmetics and U.S. Law 2005).
In order to formulate varied delivery systems, cosmetic industries, from ingre-
dients producers to end-products distributors are responsible for checking the
cosmetics’ compliance with the requirements of applicable regulations and other
relevant legislation including REACH, restriction of hazardous substances, good
manufacturing practices, etc. Thus, ingredients used to formulate cosmetic and
personal care products are usually cosmetic grade that means produced and sold
by manufacturers that checked the safety according to regulations. The Cosmetic,
Toiletries, Fragrance Association (CTFA), now The Personal Care Products
Council, created the first edition of the Cosmetic Ingredient Dictionary in 1973.
The first edition of this Dictionary contained a listing of 5000 trade and chemical
names together with their CTFA adopted names, definitions, structures, Chemical
Abstract Service Registry (CAS) numbers and other information. In 1994, the fifth
edition contained more than 6000 chemical names and was called the International
Cosmetic Ingredient Dictionary first edition of the Cosmetic Ingredient. Since
then, most countries have adopted this nomenclature and today, cosmetic
8  Cosmetics and Personal Care Products 221

ingredients are described and referred on packaging and in the ingredients list
on the label with their INCI name, a systematic name coined by the International
Nomenclature Committee. The 2014 International Cosmetic Ingredient Dictionary
and Handbook provided the most comprehensive listing of ingredients used in
cosmetic and personal care products with 21,000 monographs of INCI labelling
names (Personal Care Products Council 2015).
Cosmetic products are used by consumers for specific function or a promise of
efficiency but also mostly for the pleasure it brings to them. Thus, during many
years, cosmetic ingredients and products have been developed and produced to
fulfil these attempts, thus partly explaining the high number of ingredients avail-
able. However, consumers nowadays have become increasingly cautious on safety
and environmental issues. As a consequence, in relationship with the deep evo-
lution of the different regulations in the world since the 1970s, consumers’ con-
cerns are also to use products with a promise of safety and with a respect for living
systems and environment. So today, consumers are also particularly sensitive to
raw material selection and are looking for more “natural products”. Consequently,
different ingredient families such as animal-based ingredients, nanomaterials, pre-
servatives (e.g. parabens) suffer from a low opinion. As for many others areas,
brand image and marketing are very important in cosmetic industries and more
products on sale today which claim to possess “naturality”.
In such a context, more interests are given to ingredients issued from a natu-
ral source and for which the steps of transformation are reduced to a minimum,
with few or even no chemical reagents. Among the different classes of ingredi-
ents, natural polymers and their derivatives are an important class of ingredients,
widely used in a lot of delivery cosmetic products. The aim of this chapter is to
describe the place, the role and the use of such polymers in the cosmetic field. The
first part of this chapter gives general information on type and structure of the dif-
ferent natural polymers generally encountered and their place among the different
polymers used in cosmetic. In order to improve their functional properties, natural
polymers may be chemically modified and the principle of these modifications is
presented through the example of cellulose derivatives. Then, in a second part, the
role and properties of natural polymers in cosmetics are presented following three
main impacts on stability, rheology and during application. In order to illustrate
these two first parts, the third one details the examples of cosmetic formulations
with specific focus on how natural polymers and derivatives may be handled to be
formulated. Finally, a conclusion presents several promising innovations on those
compounds and some perspectives (see also Chap. 12).

8.2 Generalities

Polymers are one of the most important class of ingredients in cosmetics and
personal care and represent the second largest class of ingredients in this field
(Lochhead 2007). They are referenced on the label of a cosmetic product, with
222 G. Savary et al.

their INCI name in the ingredients list. It is important to note that one of the
requirements for the labelling is to first list the ingredients in descending order of
predominance by weight, if they are present at more than 1 % in the formula and
then ingredients present at a concentration not exceeding 1 % may be listed in any
order. Thus, as polymers are generally added at concentrations lower than 1 % (see
Table 8.1), they can be found at the bottom of the ingredients list.
INCI assignments for polymers are based on starting monomers rather than
resultant polymer as they are not always easily defined and can be a complex
mixture of reactants and by-products. So, for synthetic polymers, guidelines for
INCI assignments can be found in the following references. Biological materi-
als are named specifically (e.g. hyaluronic acid) when the material has been iso-
lated, purified and chemically characterized. When the end product is produced
from fermentation or microorganism culture, it has a common or usual name, such
name may be used, e.g. gellan gum, xanthan gum. Finally, botanicals are cos-
metic ingredients directly derived from plants. Generally, these ingredients have
not undergone chemical modification and include extracts, juices, waters, distil-
lates, powders, oils, waxes, gels, saps, tars, gums, unsaponifiables, and resins. As
an example, INCI name of carob or locust bean gum is Ceratonia Siliqua Gum
as it is a gum obtained from the ground endosperms of Ceratonia siliqua (INCI
Nomenclature Conventions 2015; Abrutyn 2010).
Polymer can be defined as an organic or inorganic compound, with large
dimension and a high molecular weight. It is composed of large macromolecular
chains made up with the covalent assembly of a great number of repetitive units or
monomers. In the INCI dictionary, polymers can be categorized as: organic poly-
mers, inorganic polymers, siloxane polymers and naturally occurring polymers,
classes that can be further sub-categorized (Abrutyn 2010).
This chapter only focuses on organic polymers. There are several ways to
classify organic polymers; according to their source, there are natural polymers
obtained from biosynthesis, semi-synthetic polymers obtained by chemical modi-
fications of natural polymers and synthetic polymers, obtained through polymeri-
zation reactions (step-growth or chain-growth reaction). In the case of cosmetic
products, it may also be interesting to classify those polymers according to their
electric charge, especially in the case of water-soluble polymers, which represent
an important part of this class of ingredients in this field. Thus, among polymers,
natural, modified ones (so-called artificial), and synthetic ones, nonionic as well as
anionic, cationic or amphoteric substances are available.
Polymers can be characterized by the arrangement of the atoms and repetitive
units in the chain: homopolymers are derived from one type of monomer; copoly-
mers are derived from two or more species of monomers and as a consequence
can be distinguished by the sequence of their monomer units (random, alternating,
diblock, triblock, grafted).
Two key parameters should be known to characterize polymers: its molecular
weight and its architecture. With the exception of naturally occurring proteins, all
polymers are mixtures of many molecular weights and are polydisperse and the
knowledge of the distribution of molecular weights is very important as it may
Table 8.1  Main natural polymers used in cosmeticsa
Name Origin/source Function Level Current applications in Examples of derivatives used in
(%) cosmetics cosmetics
Xanthan Biotechnology Thickener; emulsion 0.1–1 Skin care; haircare; None
stabilizer; suspending conditioners; toothpaste;
agent aftershave; shower gel;
shower cream; body lotion;
shampoo; sunscreen;
cleanser…
Hyaluronic acid +  Moisturizer, softening 0.1–2 Moisturizing cream and None
hydrolysis products agent lotion; hydrating gels,
anti-ageing and anti-wrinkle
products, pre/after sun lotions,
8  Cosmetics and Personal Care Products

protecting and nourishing

products…
Sclerotium gum Thickener; emulsion 0.02–1 Skin care: lotions, creams, None
stabilizer; suspending face masks… sun care
agent lotions; bath and shower
gels and washes; hair care
(shampoo)…
Cellulose + Vegetal Thickener; film former; 0.5–2 Skin care; lipstick; See detail in Table 8.2
Microcrystalline absorbant; foundation; face, body and
cellulose opacifiant; hand products; eyeliner;
Charge; softening agent moisturizing products;
mascara; hair dyes and
colours; bath preparation;
shampoos; toothpaste;
antiperspirant…
(continued)
223
Table 8.1  (continued)
224

Name Origin/source Function Level Current applications in Examples of derivatives used in

(%) cosmetics cosmetics
Starch (maize, potato, Vegetal (plant Thickener; conditioner; 3–10 Conditioning; body and Aluminium starch octenyl succinate
tapioca…) Including seed) powder (charge): make-up powders; Distarch phosphate
maltodextrin softening agent antiperspirant; colour Hydroxypropyl starch phosphate
cosmetics; creams; lotions; Starch hydroxypropyltrimonium
eye cosmetics; face scrub; chloride
liquid make-up; liquid talc…
Galactomannan gums Thickener; film former, 0.1–1 Skin care; hair care Hydroxypropylguar (hpg)
(guar and locust bean) stabilizer Guar hydroxypropyltrimonium
chloride
Locust bean hydroxypropyltrimo-
nium chloride
Hydrolyzed wheat Conditioner; film for- 0.5–5 Skin care, haircare Hydr wheat protein dimethicone
(hydr wheat) mer; tensor; antistatic peg-7 acetate
Hydr wheat protein peg-20 acetate
copolymer
Hydr wheat protein polysiloxane
copolymer
Acacia gum Vegetal Thickener; dispersing 1–10 Cleanser; creams; lotions; None
(plant exudate) agent; foam and balms; pomades; shampoos;
emulsion stabilizer; body washes; make-up prod-
adhesive; film former ucts (e.g. Mascara, brow and
lash gels)…
Carrageenan gum Vegetal (seaweed) Thickener; gelling 0.2–1.2 Toothpaste; skin care; cream None
(kappa, iota, lambda) agent; film former
Alginate and alginic Thickener, suspending 0.2–2 Skin care; styling products; Propylene glycol alginate
acid agent; film-forming toothpaste
(continued)
G. Savary et al.
Table 8.1  (continued)
Name Origin/source Function Level Current applications in Examples of derivatives used in
(%) cosmetics cosmetics
Hydrolyzed keratin Animal or vegetal Conditioner; moisturizer 0.2–5 Shampoos; hair conditioners; Cocodimoniumhydroxypropylhydr.
(hydr.keratin) hair balms; hair pomades; keratin
skin care products including Cocodimoniumhydroxypropylhydr.
lotions and creams… keratin
Hydr.keratinpg-
propylmethylsilanediol
Collagen, gelatin, and Animal Conditioner; 0.2–2 Skin care; haircare; Cocodimoniumhydroxypropylhydr.
hydrolyzed collagen moisturizer; hydrating; anti-ageing and moisturizing collagen
(hydr.collagen) film-forming lotions; serums; sun care and Lauryldimoniumhydroxypropylhydr.
after sun products; make-up collagen
8  Cosmetics and Personal Care Products

products; hair conditioners; Isostearoylhydr.collagen

shampoos; hair masks…
Chitosan, hydrolyzed Thickener; conditioner; 0.25–1 Hair care, skin care Chitosan lactate
chitosan and chitin chelating agent; Chitosanpyrrolidonium carboxylate
hydrating, film former
Hydrolyzed silk (hydr. Hair conditioner; 0.2–2 Haircare; shampoo; mask Hydr.silkpg-propylmethylsilanediol
silk) +antistatic; humectants Sodium lauroylhydr.silk
aSources Le Flacon (2015), Lochhead and Gruber (1999), Making Cosmetics (2015), Official Journal of the European Union (2009)
225
226 G. Savary et al.

influence properties such as the rheology of melts and solutions, adhesion and age-
ing behaviour. Furthermore, architecture of a polymer affects physical, functional
and/or chemical properties. Chains can be structured in many different ways: lin-
ear, branched, side chains, rigid rod, macrocycle, star polymers, comb polymers,
brush polymers, dendrimers, cross-linked polymers. Finally, polymers can be
amorphous or semi-crystalline, depending on the chains arrangement and ordering.
Due to their marked properties, even at low content, polymers are used in
small quantities to exert various functions in formulations: rheology modifiers,
e.g. thickeners/surface active modifiers such as surfactants, emulsifiers and wet-
ting agents/solubility modifiers including coupling agents and dispersants/bulking
agents, preservatives, skin and hair conditioners, sunscreen agents/coating agents,
encapsulants/abrasive, exfoliants (Abrutyn 2010).
Natural polymers or biopolymers include proteins, polysaccharides, natural
rubber, resins and gums. Proteins and polypeptides are constituted of amino acids
linked by an amide linkage or peptide bond between the amino group of one mol-
ecule and the carboxyl group of another. Most proteins derivatives for cosmetic
purposes are obtained from simple proteins (fibrous and globular) while conjugated
proteins (proteoglycans and nucleoprotein derivatives) are far less frequently used.
Main proteins and protein derivatives used in cosmetic products are obtained from
animal and vegetable sources. Collagen, elastin, keratins, milk and silk proteins are
the first and most successfully used in the modern cosmetics industry and are from
animal sources. They are currently used as water-soluble derivatives, suitable for
cosmetic use, and are obtained from partial hydrolysis of native form. The success
of such ingredients is also related to their wide availability at low cost and high-
purity but also because of their high tolerance as human skin and connective tissues
are constituted by the same proteins. Due to their animal sources and loss of popu-
larity since last decades, proteins issued from vegetable and plant sources have been
more developed; in particular, interest in proteins and hydrolyzed derivates from
wheat gluten and soy have been growing a lot. These last ingredients are reported in
Table 8.1 with their level of use and current functions in cosmetic products. The first
rational use of proteins and peptides in cosmetics dates to the 1950s and since the
beginning of the 1960s, their binding properties to skin and hair and substantively
to hair were investigated and demonstrated. Today, numerous protein derivatives are
developed to enhance their functionalities but also to find new protein sources. As
they are mainly used as actives, their roles will be detailed in Sect. 8.3.3 dealing
with the sensory and properties during application (Teglia and Secchi 1999).
Polysaccharides are composed of simple carbohydrates linked to each other by
acetal bonds. Main polysaccharides used in the cosmetic industry are reported in
Table 8.1. This list is not exhaustive and we decided to highlight the ones whose
occurrence is most important in industrial products. Like alginates, pectins and
carrageenans, xanthan is an anionic polysaccharide. It is obtained by bacterial
fermentation and as a complex structure comprising a primary chain of glucose
which has, on alternating glucose moieties, a branching trisaccharide side chain.
Thus, in solution, xanthan generally forms helical coils characterized by a rigid
backbone and is an excellent suspending agent. Its properties are mainly described
8  Cosmetics and Personal Care Products 227

in Sects. 8.3.1 and 8.3.2 concerning stabilizing and rheological properties of natu-

ral polymers; in addition, sensory characteristics of this important cosmetic ingre-
dient are also presented in Sect. 8.3.3.
Hyaluronic acid is also an anionic polysaccharide, isolated from various animal
tissues and commercially manufactured by bacterial fermentation. It is made of
two repeating monosaccharides: glucuronic acid and N-acetyl-glucosamine. It is
mainly used for topical purposes and as an active, as it is described in Sect. 8.3.3.
Finally, among anionic polysaccharides, acacia gum is one of the oldest and most
commercially well-established. It is extracted from exudate gums of specific trees
(Acacia Senegal for instance) and is comprised of a neutral backbone of galactose
units that have multiple branching glycans. It is characterized by a relatively low
molecular weight and thus is used in applications where high levels of polysaccha-
ride are desired without enhancing viscosity. It is an emulsifying agent supplying
stabilization properties to complex multiphase systems as noted in the Sect. 8.3.1.
Chitosan is the only naturally occurring polysaccharide to be cationic. This
property is only shown at pH below seven. The advantage of being cationic is the
ability to bind strongly to anionic surfaces like human and hair skin. Chitosan is
a random copolymer comprised of two monosaccharides, N-acetyl-b-d-(1,4)-
glucosamine and b-d-(1,4)-glucosamine generally in a 1:4 ratio in commercial
materials. Besides the substantive application to hair and skin owing to the cati-
onic property; chitosan is also used as a film-forming agent in fixative products
and 2-in-1 shampoos. This polymer is principally described in Sect. 8.3.3. The two
other cationic polysaccharides extensively used in cosmetic are cationic deriva-
tives of cellulose and guar, cited in Sects. 8.3.1 and 8.3.3.
Cellulose, starch, galactomannan and sclerotium gums are nonionic polysac-
charides. Together, cellulose and starch represent the most abundant polysaccha-
rides available for commercial exploitation. They are composed of one repeating
monosaccharide, glucose, linked to each other by β-d (1,4) or α-d (1,4) bonds,
respectively. Sclerotium gum is also composed of repeating glucose moieties but
linked through β-d (1,3) linkage together with a branching of glucose and is a
good suspending agent like xanthan. However, unlike cellulose or starch, sclero-
tium gum has limited uses in personal care.
Galactomannans, guar and locust bean gum more specifically, have a back-
bone of β-d-(1,4)-mannose with a branching of α-d-(1,6)-galactose. Guar is more
substituted than locust bean and can be characterized as a comb-like polymer.
Although locust bean gum has received limited use in the personal care industry,
guar is an important natural thickening agent for aqueous compositions and brings
lubriciousness or silky feel to those compositions (Gruber 1999).
Due to their chemical composition and also the conformation of their macro-
molecular chains, those nonionic polymers often show a weak or complex solubil-
ity in water; thus, in order to improve and enhance their interactions with different
solvents, many semi-natural derivatives are prepared from cellulose, guar or starch
polysaccharides. Those derivatives are extensively used in personal care products
when compared to the native ones. Few examples are mentioned in Table 8.1, such
as hydroxypropyl guar or maltodextrin (Gruber 1999).
228 G. Savary et al.

To better understand the principle of such modifications, a focus on cellulose

modification is proposed (Table 8.2). Cellulose is a polydisperse linear homopoly-
mer, consisting of β-1,4-glycosidic linked d-glucopyranose units [so-called anhy-
droglucose units (AGU)]. The polymer contains free hydroxyl groups at the C-2,
C-3 and C-6 atoms.
The abundance of hydroxyl groups and concomitant tendency to form intra-
and intermolecular hydrogen bonds results in the formation of linear aggregates
of helical structures. In the solid state, highly ordered crystalline areas are inter-
spersed between less ordered amorphous zones. Consequently, as cellulose is
insoluble in water, conversion to water-soluble derivate forms is usually required
for cosmetic uses. This can be done either physically or chemically (Gruber 1999;
Zecher and Gerrish 1999).
Disruption of the hydrogen bonds can be accomplished by cellulose derivatiza-
tion. To that purpose, the native polymer is first submitted to aqueous alkali con-
ditions to induce swelling of the cellulose fibres prior to further treatment. Then,
alkali-cellulose may be treated by sodium chloroacetate to produce carboxym-
ethylcellulose, an anionic derivative, or with various alkylating agents, to produce
nonionic cellulose ethers: hydroxyethyl cellulose (HEC), hydroxypropyl cellulose
(HPC), methyl cellulose (MC) and hydroxypropylmethyl cellulose (HPMC) are
among the most popular and useful rheology modifiers employed in the personal
care industry (Gruber 1999; Zecher and Gerrish 1999).
The corresponding polymer properties are governed by the extent of the sub-
stitution. This last parameter is expressed as the degree of substitution (DS) or the
molar substitution (MS). As each anhydroglucose unit (AGU) contains three free
hydroxyl groups available for reaction, the polymer may have a maximum degree
of substitution (DS) of three where DS is defined as the average number of sub-
stituent groups per anhydroglucose unit.
When alkylene oxides (HEC, HPC, HPMC, etc.) are used, new hydroxyl sub-
stituent groups are formed that can further react. Thus, the extent of substitution
is better characterized as the molar substitution (MS), where MS is defined as the
average number of moles of substituent groups per AGU. For instance, hydroxye-
thyl cellulose is commonly manufactured with a MS of 1.8–2.5 but various grades
range from an MS of 1.5–3.0. Cellulose gum or carboxymethylcellulose is cur-
rently manufactured with DS ranging from 0.65 to 1.45. For both, solution viscosi-
ties greatly vary, depending also on the molecular weight of the product (Review
Expert Panel 2009).
Hydroxyethyl cellulose (HEC) can be further derived with various cationic
reagents to randomly add quaternary cationic charges along the HEC backbone.
Known by their INCI name as polyquaternium-10 or polyquaternium-4, those cati-
onic derivatives are extensively employed as conditioner or conditioning and fixa-
tive adjuvant, respectively, in hair and skin care formulations (Gruber 1999).
At last, cellulose can be physically treated to produce microcrystalline cellulose
(MCC) which is prepared by treating wood pulp and linters with dilute mineral
acid and is described as purified, partially depolymerised cellulose with a degree
of polymerisation (DP) below 350. MCC is basically made of crystallites of
Table 8.2  Main modified cellulosesa
INCI Name Description Function Examples
Cellulose Natural polysaccharide derived Absorbent, bulking, opacifying, Foundation, facial scrub, face mask,
from plants fibres viscosity controlling eyeliner
Linear polymer of β-1,4-d-glucose
Microcrystalline Cellulose Purified, partially depolymerised Absorbent, anticaking, bulking, Moisturizing cream, shower gel,
fraction of α-cellulose. Isolated, emulsion stabilizing, opacifying, anti-ageing fluid, hand cream
colloidal crystalline portions viscosity controlling
of cellulose fibres
Anionic cellulose derivatives
Cellulose gum (sodium Sodium salt of the polycarboxymethyl Binding, emulsion stabilizing, Toothpaste, moisturizing cream, anti-
carboxymethylcellulose) ether of cellulose. Reaction film forming, masking, viscosity wrinkle fluids and creams, skin care
of sodium chloroacetate controlling
8  Cosmetics and Personal Care Products

with alkali-treated cellulose

Nonionic cellulose derivatives
Cellulose Acetate Butyrate Butyric acid ester of a partially Film forming Serum, moisturizers, skin care, nail
acetylated cellulose care
Cetyl Hydroxyethylcellulose Ether of cetyl alcohol and hydroxy- Emulsion stabilizing, film forming, Hair care, shaving foam, hair lotion,
ethylcellulose. Reaction of alkali- viscosity controlling body gel
cellulose with ethylene oxide
followed by a cetyl substitution
Ethylcellulose Ethyl ether of cellulose Binding, film forming, viscosity Skin care, skin cleansers, lip balm
controlling
Hydroxyethylcellulose Ethylene glycol ether of cellulose Binding, emulsion stabilizing, Skin care, deodorant, serum, hair
Reacting alkali-cellulose with ethylene film forming, stabilizing, viscosity care, shaving gel, mascara
oxide in the presence of alcohol or controlling
acetone
Hydroxypropylcellulose Propylene glycol ether of cellulose Binding, emulsifying, emulsion Colognes and toilet waters, hair
(reacting propylene oxide with alkali- stabilizing, film forming, viscosity conditioners, aftershave lotions,
treated cellulose) controlling moisturizers
229

(continued)
Table 8.2  (continued)
230

INCI Name Description Function Examples

Hydroxypropyl Methylcellulose Propylene glycol ether of methyl Binding, emulsion stabilizing, Facial scrub, paste and treatment
cellulose. Methyl chloride film forming, surfactant, viscosity mask, masks, bubble baths, shaving
treatment of hydroxypropyl cellulose controlling cream
Methylcellulose Methyl ether of cellulose. Reaction Binding, emulsion stabilizing, viscos- Body lotion, shampoos, cleansers
of methyl chloride with alkali-treated ity controlling
cellulose
Nitrocellulose Nitrate esters of cellulose. Treatment Film forming Nail polishes and enamels
of cellulose by nitric and sulfuric acids
Cationic cellulose derivatives
Polyquaternium-10 Cationic hydroxyethyl cellulose Antistatic, film forming Shampoos, body cleansers, hair
Reaction of alkali-treated hydroxy- conditioners
ethyl cellulose with a cationic epoxy
(2,3-epoxypropyltrimethylammonium
chloride)
aSources Le Flacon (2015), Lochhead and Gruber (1999), Official Journal of the European Union (2009), Review Expert Panel (2009)
G. Savary et al.
8  Cosmetics and Personal Care Products 231

colloidal size. The crystallite aggregates, forming particles, which in turn agglom-
erate during drying of the cellulose slurry to reach a final mean particle size
between 20 and 200 µm. Microcrystalline cellulose is a diluent with very good
binding properties for direct compression (compaction of tablets for instance) and
due to its insolubility, it provides a “gel” network with pseudoplastic, highly shear
thinning and thixotropic properties (Thoorens et al. 2014).
To conclude, polysaccharides in the solution can exist as loose random coils or
rigid helices. They can be anionic, cationic, nonionic or even amphoteric depend-
ing on their chemical composition. They can be single coils, double coils and even
aggregates of coils; the nature of which can be influenced by, among other things,
temperature, concentrations and other species such as salts.
For all these reasons, natural polymers, gums and resins have been used in the
industry since the early 1940s as water-soluble binders, thickeners and film-form-
ing agents. Those properties are highlighted in Sects. 8.3.1 and 8.3.2 dealing with
the stabilizing and rheological properties of natural and nature modified polymers
as illustrated through examples in the cosmetic field.
Unfortunately, use of polymers obtained from natural sources has some dis-
advantages: they vary in purity and physical appearance which imply variations
in viscosity and microbial contamination, and are relatively expensive when
compared to the ones obtained by synthetic routes. These variations are due to
the difficulty to obtain stable supplies. As a consequence, those features histori-
cally led to a change to synthetic or semi-synthetic substitutes (Winnick 1999).
At the beginning, in the 1950s, synthetic or semi-synthetic polymers have been
developed to match the properties of gums and resins. Since 1970s, carbomers,
polymers obtained from acrylic acid, have dominated the market of thickening and
stabilizing agents used in emulsions and lotions. In the 1990s, hydrophobically-
modified versions of carbomers (Acrylates/C10-30 alkyl Acrylate Crosspolymer)
were introduced, combining emulsifying and rheology-modifying properties.
Other synthetic polymers used for cosmetic purposes are acrylamides copoly-
mer, simple vinyl polymers, crosspolymers like acrylates/VA (Vinyl Acetate)
crosspolymer, alkoxylatedhomopolymeric ethers based on ethylene oxide or pro-
pylene oxide. So, until recently, chemical synthesis of synthetic polymers made
it possible to tune several required properties (thickening, associative properties,
emulsifying) with one ingredient or a mixture of synthetic ingredients leading to
improved formulations.
However, today there is a growing consumer demand for natural products,
safety profile of ingredients and use of renewable resources which give a renewed
interest in natural polymers. Section 8.3.3 of this chapter presents new research on
the sensory properties brought by natural and natural modified polymers. Finally,
it is also important to keep in mind that most part of cosmetic products and per-
sonal care must comply with quite a long period after opening (PAO), at least 6 or
12 months. Thus, stabilizing and maintaining physicochemical as well as sensory
properties and, of course, the consumer security for these products over a wide
period of time is a challenge. To do so, as can be noticed in Sect. 8.4 of this chap-
ter, dealing with examples of cosmetic formulations including polymers, synthetic
232 G. Savary et al.

and natural polymers coexist with relatively high amounts of synthetic emulsifiers
that are conjugated with fatty alcohol, in order to create organized structures in the
emulsions (liquid crystalline phase) and to obtain products with consistency that
can support long-time ageing. Further details on synthetic polymers used and role
of polymers in cosmetic product can be obtained in Goddard and Gruber (1999),
Lochhead (2007, 2010).

8.3 Functions of Natural Polymers in Cosmetic Products

8.3.1 Impact on the Stability

8.3.1.1 Cosmetic Products: Complex Systems Subjected

to Destabilization

When cosmetic and toiletry products are developed, they have to fulfil a number of
requirements: they have to provide a function (cleaning hair and skin, protecting
against sunburst, etc.), to enhance the psychological well-being of consumers by
increasing their aesthetic appeal (for example impart a pleasant odour and making
the skin feel smooth) while insuring medical safety as they come in close con-
tact with various organs and tissues like hair and skin, and sometimes the mucous
membrane. The different ingredients constituting the formulations must be chosen
with respect to the biological and physicochemical properties of those substrates;
in a formulation, they are numerous and could be oil, water, surfactants, pigments,
UV filters, colouring agents, fragrant, preservatives, conditioning agents, vitamins
amongst others. Different delivery systems—emulsions, suspensions, foams, solu-
tions—are prepared to optimize the effects and benefits of the different compo-
nents (Tadros 2008). These complex systems are generally included as colloidal
systems.
Emulsions are one of the most common delivery system used in cosmetics.
They consist of mixtures of at least one liquid dispersed in another in the form of
droplets, both liquids being immiscible or poorly miscible. They are classified as
follows:
• Macroemulsions: simple emulsions that can be Oil-in-Water (O/W) or Water-
in-Oil (W/O) like lotions and creams. Droplet sizes generally range between 0.1
and 100 µm.
• Nanoemulsions: simple emulsions (O/W or W/O) for which droplet sizes range
between 20 and 200 nm.
• Multiple emulsions: More complex systems like oil-in-water-in-oil or water-in-
oil-in-water with droplet sizes similar to the ones in macroemulsions.
• Microemulsions: system of water, oil and both surfactant and co-surfactant
which is a single optically isotropic and thermodynamically stable liquid solu-
tion. Droplet sizes range from 10 to 100 nm.
8  Cosmetics and Personal Care Products 233

Solid/liquid dispersions or suspensions are dispersed systems currently used in

cosmetics. These can be classified as follows:
• Suspensions: dispersions of solid particles in a liquid continuous media (pig-
ments, solid actives, clay, mechanical facial scrubs particles, polyamide
particles,etc.) like lipsticks or nail polishes and also shampoos or shower gels
containing particles. Particle sizes generally range from 0.1 to 100 µm;
• Nanosuspensions: particle sizes range from 20 to 200 nm.
Both emulsions and suspensions are combined to form emulsions–suspensions
mixture or suspoemulsions like in the case of foundations where pigment particles
are usually dispersed in the continuous phase of an O/W or W/O emulsion.
Except for microemulsions, all previous systems are thermodynamically insta-
ble and submitted to different destabilization mechanisms described below.
Similar for emulsions and suspensions, creaming and sedimentation depend on
the size of the particles/droplets and the density difference between the particle
and the medium. Those phenomena are more intense for sizes larger than 1 µm
and density difference larger than 0.1 which occurs very frequently in cosmetic
products. Creaming and sedimentation can be avoided or strongly reduced by
enhancing viscosity of the continuous phase which can be done by using “thicken-
ers” like polymers. If the droplet size or the particle size is reduced to 20–200 nm
like in nanoemulsions or suspensions, respectively; then, Brownian diffusion over-
come gravity and the systems are physically stable, without apparition of other
destabilization mechanisms.
Flocculation is the result of an attractive interaction between particles or drop-
lets. It can be weak or strong depending on the magnitude of the attractive energy.
Weak flocculation is in some cases reversible by re-stirring and may also occur
by two other mechanisms: bridging and depletion. Bridging flocculation may arise
when a single polymer macromolecule weakly adsorb at the surface on more than
one suspension particle or emulsion droplet. Depletion flocculation is produced
by the addition of a non-adsorbing polymer. Increase of osmotic pressure around
droplets results in exclusion of polymer species from the surface of particles and
the formation of depleted zones and weak attraction between particles. For further
information, see Tadros (2008) and Bouyer et al. (2012).
Strong flocculation leads to formation of aggregates that can further sediment
or cream; in the case of highly concentrated suspension or emulsion, the particles
or droplets create a three-dimensional “gel” structure. When flocculated structures
are not re-dispersible or in the case of strong flocculation, this is the starting point
of further sedimentation or creaming phenomena and especially coalescence in
the case of emulsions or coagulation in the case of suspensions are nonreversible
mechanisms. Coalescence is first the thinning and then the disruption of the liq-
uid interfacial film between droplets until macroscopic oil–water phase separation.
Coagulation is the formation of strong aggregates sediment or clusters forming
compact structures. Both structures must be avoided.
234 G. Savary et al.

Finally, emulsions may undergo Ostwald ripening that is a diffusion mecha-

nism of smaller droplets, due to their solubility in the external phase, into larger
ones. This phenomenon may lead to the separation of the phases and is also
nonreversible.

8.3.1.2 Stabilizing Properties of Natural Polymers in Cosmetic

Emulsions and Suspensions

Natural and semi-synthetic polymers are used in personal care as rheology modi-
fiers to achieve stability against settling during storage. Natural polymers con-
cerned here include casein, alginates, guar gum, xanthan gum, tragacanth gum
and semi-synthetic include modified cellulose such as carboxymethyl cellulose,
methylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose (Lochhead
2007, 2010). Unlike the food area, in the cosmetic field, proteins and their deriva-
tives are mostly used as active ingredients and polysaccharides are often used to
stabilized emulsions and suspensions, all together combined with synthetic poly-
mers like carbomers (see Sect. 8.4—Examples of formulas) and, in addition, small
molecular weight emulsifiers, in order to confer the desired delivery characteristics
such as smoothness. Those properties are focused in Sects. 8.3.2 and 8.3.3 of this
chapter. As they are, for the most part of them, hydrophilic, it generally concerns
formulations in which the continuous liquid phase is aqueous and they are mainly
used to prevent creaming and sedimentation.
The mechanism of stabilization depends on adsorption ability of the macro-
molecules. Some adsorb at the oil–water interface while others only modify the
aqueous phase viscosity due to their non-adsorbant nature. Rozanska et al. (2013)
have compared the stabilizing effects of guar gum (GG), hydroxypropylmethyl
cellulose (HPMC), carboxymethyl cellulose (Na-CMC) and xanthan gum (XG).
O/W emulsions containing 20 and 40 vol% of dispersed phase were produced with
0.4 wt% GG and HPMC, 0.5 % Na-CMC and 0.1 and 0.2 wt% for XG. As non-
adsorbing polysaccharides, XG, GG and Na-CMC exhibit emulsions with aggre-
gated droplets due to depletion flocculation (Fig. 8.1a, e and f). The depletion
forces are higher with increasing molar mass of the polymer and with polyelectro-
lytes (Na-CMC emulsion more flocculated that one with GG) and are stronger at
low polymer concentration (0.1 wt% XG emulsion show bigger agglomerates than
0.2 wt% XG emulsion). HPMC adsorbs at the droplets surface and bridging floc-
culation is evidenced thus producing agglomerates similar to GG and 0.2 wt% XG
emulsions. Authors show that those different flocculated states have an impact on
rheological properties, as at low shear rate the rheological properties of emulsions
depend on the size of aggregates made up of single oil droplets, which in turn may
have an impact on stability of the emulsion.
Xanthan gum is one of the most widely occurring polysaccharide in cosmetic
emulsions, as can be seen in the different formula given to illustrate utilization of
natural polymers in the Sect. 8.4. Thus, a great number of research papers, dealing
with cosmetic emulsions (Mostefa et al. 2006) or “simplified” or model emulsions
8  Cosmetics and Personal Care Products 235

Fig. 8.1  Microscopic pictures of emulsions with addition of GG 0.4 wt%, φ  = 20 vol% (a);

HPMC 0.4 wt%, φ = 20 vol% (b); XG 0.1 wt%, φ = 20 vol% (c); XG 0.2 wt%, φ = 20 vol%
(d); XG 0.1 wt%, φ = 40 vol% (e); Na-CMC 0.5 wt%, φ = 20 vol% (f) (from Rozanska et al.
2013) with permission from Elsevier, Licence number 3634200640618

(Krstonosic et al. 2009, 2015; Vianna-Filho et al. 2013; Ye et al. 2004) have stud-
ied the effect of this polymer on the emulsions stability. The major results of those
studies is that stability of emulsions mainly depends on xanthan gum concentra-
tion: in the study of Krstonosic et al. (2015), whatever the xanthan gum concen-
tration (between 0.01 and 0.2 wt%) in the continuous phase, droplets flocculation
occurs. Under a certain value (0.08 wt%), creaming is enhanced, and produces
a phase separation in the emulsion, while above this value, emulsions contain-
ing higher xanthan concentration exhibit a delayed time in creaming. It has been
reported that above a critical concentration, xanthan gum induces the establish-
ment of a three-dimensional gel-like droplets network (Ye et al. 2004; Krstonosic
et al. 2009; Aben et al. 2012). When xanthan concentration is still increased, less
flocculation appears (>0.6 % in the study of Ye et al. 2004) and emulsions are then
mostly stabilized by the continuous phase viscosity increase. Thus, Mostefa et al.
(2006) show with experimental design that the most important parameter is the
xanthan concentration. It has a positive influence in the range of [1 and 2 %] on
the stability of a depilatory cream, in relationship with high viscosity of the aque-
ous phase of the oil-in-water emulsions. Hydroxyethyl cellulose is also widely
used as thickener and rheology modifier to stabilize emulsions and suspensions.
As Starch, alginates, carrageenans, hyaluronan, chitosan, it is considered as non-
adsorbing polysaccharides.
Some other polysaccharides such as acacia gum, naturally occurring galac-
tomannans (guar and carob), pectin and chemically modified starch or cellulose
derivatives exhibit interfacial activity (Bouyer et al. 2012). Due to their amphiphi-
lic character, they adsorb at the interface of the oil droplet, stabilizing the emul-
sion and through electrostatic and/or steric repulsive forces hinder flocculation and
236 G. Savary et al.

coalescence. In the case of acacia gum and pectin, this surface activity is related to
the presence of a protein fraction in the structures such as for, but less obviously,
galactomannans (Bouyer et al. 2012; Vianna-Filho et al. 2013).
In order to improve interfacial properties, starch and cellulose have been chem-
ically modified to introduce hydrophobic/hydrophilic groups along the macromol-
ecules backbone. Hydroxypropylmethyl cellulose, hydroxypropyl cellulose and
new derivatives from hydroxyethyl cellulose such as ethyl hydroxyethyl cellulose,
methyl hydroxyethyl cellulose and hydrophobically-modified ethyl hydroxyethyl
cellulose are known to exhibit high surface activity when compared to HEC (Asad
2011). Sun et al. (2007) studied the adsorption and thickening effect of hexade-
cyl modified hydroxyethyl cellulose compared to the hydroxyethyl cellulose. More
than a polymeric surfactant, such a hydrophobically-modified polymer behaves
as an associative polymer: it adsorbs at the oil/water interface due to penetration
of the alkyl chains into the oil phase and shows much better thickening ability
which is caused by the intermolecular association of the hydrophobic alkyl chains.
Therefore, emulsions stability is the result of an associative thickening mechanism
caused by alkyl chains, combined with the adsorption of hydrophobically-modi-
fied hydroxyethyl cellulose at the oil–water interface, which can form a solid film
preventing droplets coalescence.
Starch may be hydrophobically-modified via octenyl succinic anhydride
to produce OSA starch that can be used as emulsifier in oil-in-water emulsions
(Krstonosic 2015). OSA starch may play the role of both an emulsifier and an
emulsion stabilizer: the short octenyl succinate side chains adsorb at the oil–
water interface while the large amylopectin backbone provides steric stabilization
against flocculation. Recent studies focused on formation of Pickering emul-
sions, that are particle stabilized emulsions and so surfactants free emulsions, with
hydrophobically-modified starch particles (Marku et al. 2012) or hydrophobized
cellulose nanocrystals (Capron and Cathala 2013).

8.3.1.3 Role of Natural and Semi-synthetic Polymers in Cleansing

Products

Shampoos and conditioners are the highest volume of products sold in personal
care. The principal function of a shampoo is to cleanse the hair. However, modern
shampoos should at least cleanse, make the hair easier to style, and fragrance the
hair with a pleasant, lingering smell (Lochhead 2012). Shampoos consist essen-
tially of water, primary surfactant, one or more co-surfactants and soluble salt.
Other ingredients are added for fragrance, preservation, conditioning and styling
attributes. Primary surfactant is generally an anionic surfactant and the co-sur-
factant often called the foam booster is generally a betaine.
One essential attribute of a shampoo is its ability to produce rich foam. As
complex systems previously described, foams may also be included in colloidal
8  Cosmetics and Personal Care Products 237

complex systems as they are heterogeneous multiphasic systems composed of

high volume fraction of gas and liquid. During cleaning process, foams are created
by incorporating air during friction of shampoo on the wet hair. Foams are made
of gas bubbles separated from each other by lamellae that are thin liquid films
between two bubbles and plateau border, the region were three lamellae are join-
ing together. During shelf life of foams, bubbles turn from spherical shape to poly-
hedral shape due to continuous drainage of the liquid and consequently thinning of
the film between bubbles. Dramatic situation arises when lamellae are disrupt and
bubbles burst. These are the two main mechanisms of foams destabilization.
It has been demonstrated that utilization of cationic polymers hinders drainage
of the lamellar liquid; for this reason cellulose and guar cationic derivatives are
extensively used in this field of cleansing personal care.
Thus, polyquaternium 24, a hydroxyethyl cellulose reacted with a lauryl dime-
thyl ammonium epoxide, provides conditioning attributes but also increases stabil-
ity of oil-in-water emulsions and increases foam stability of aerosol mousses. Guar
hydroxypropyltrimonium chloride is an excellent thickener, with suspending and
stabilizing properties, combined with conditioning properties (Hoshowski 1997).
Polyquaternium-10 (see cellulosic derivatives Sect. 8.2, Table 8.2) is a
hydroxypropyltrimethyl ammonium chloride ether of hydroxyethyl cellulose. With
cationic guar, it is one of the most occurring cationic conditioning polymers in
hair and skin care products, and more specifically in shampoos. Those polymers
impart great deposition on hair for the corresponding shampoos.
In order to improve properties of conditioning and cleansing products, a lot of
works have been realized to understand the interactions between surfactants and
polymers in solution and to further use those interactions in formulations. For
further details, see Lochhead (2007, 2010, 2012), Goddard (1999), Llamas et al.
(2014) and Bureiko et al. (2014).
At last, as they are compatible with most shampoo ingredients, cellulosic deriv-
atives such as methyl cellulose, hydroxypropyl cellulose and hydroxyethyl cellu-
lose may also be added to the formulation; they are widely used in shampoo as
thickening agents, to achieve desired viscosity; such cellulose derivatives also
provide stabilizing effects in the case of conditioning shampoos or more complex
shampoo formulations incorporating emollients like silicones or oils, and also
solid particles.
Finally, it is noteworthy that cosmetic products are complex mixtures of many
ingredients in interaction. Natural polymers are stabilizing agents but their ability
may be reduced or improved according to the presence of the other ingredients.
For this reason, it is not always possible to predict the impact of the polymer on
the stability of a blend.
In this section, we mention that polymers may stabilize colloidal systems
owing to an enhancement of the viscosity. In the following section, it is explained
how the impact of polymers on the rheological properties exceeds largely a simply
stabilizing function.
238 G. Savary et al.

8.3.2 Impact on the Rheological Properties

8.3.2.1 Rheology of Cosmetics: A Key from Manufacturing

to End-User

Developing cosmetics requires controlling the rheological properties at the differ-

ent steps of product life, from the initial raw material processing until the final
utilization of product by consumers. Like in many other domains dealing with
complex mixtures elaboration, rheology allows understanding and optimizing
product development; rheology dimension has therefore to be considered for the
entire manufacturing process: raw material and mixture quality control, production
steps, stability considerations, final product characteristics and usage performance.
The ease of picking of a cream from its container, the lotion pumping ability, the
nail varnish spreading and film-forming capacity when drying, the hair-condition-
ing ability, the hair shaping/fixing of a hair fixer, the toothpaste squeezing out of
a tube and shape integrity once on the brush, the soap flow capacity, etc., are few
examples where product rheology has to be considered. In addition, more than
in many other fields, the rheological properties are of primary importance for the
consumer sensory perception and acceptance, as criteria for choosing a cosmetic
product are unambiguously associated to texture, performance (e.g. cream hydra-
tion, lipstick film thickness and homogeneity) and pleasure sensation all over the
product usage, ranging from the product shape before application to the final per-
ception once the product applied (e.g. residual film softness). As cosmetic manu-
facturers permanently need to adapt the product to the consumer expectations, aim
to fit to the market changes and also to develop innovating products, controlling
the products rheology is a key aspect to be considered. For all these reasons, since
many years the cosmetic industry considers rheology as one of the most promising
tools allowing predicting the product sensory attributes and so the consumer’s final
choice (Tranchant et al. 2001).
Like in several other domains, rheology is currently used in the cosmetic
industry to investigate the role of functional ingredients (such as polymers used
as thickeners), the resulting microstructure and the stability of complex mixtures,
the scale up of new developments and the process reproducibility. In addition,
recently, few studies using rheology have been published with the aim to corre-
late sensory data to the rheological properties of cosmetic products (Dimuzio et al.
2005; Lukic et al. 2012a; Gilbert et al. 2013b).

8.3.2.2 Natural Polymers and Derivatives as Rheological

Agents in Cosmetics

Cosmetic products cover a wide diversity of forms, ranging from monophasic sys-
tems including fluids, viscous solutions or gels, highly elastic emulsions, semi-
solid or solid dispersions and powders. Among the various ingredients governing
8  Cosmetics and Personal Care Products 239

the mixtures physical characteristics, like in many other domains polymeric spe-
cies are widely used for controlling the general product flow and viscoelastic
properties. Furthermore, biopolymer dispersions show a variety of rheological
behaviours in relation with their molecular structure and conformation. Among
the numerous cosmetic applications, polysaccharides and derivatives are more cur-
rently incorporated in the continuous phase of oil-in-water (O/W) emulsions to
control the consistency (Bais et al. 2005; Tadros 2004).

8.3.2.3 Natural Polymers to Control Formulations Stability

and Texture

As previously mentioned in Sect. 8.3.1, cosmetic products have first of all to

be stable over a fairly long period of time (often over 30 months) and the pol-
ymers stabilizing efficacy is currently employed for reaching sufficient lifetime.
Basically, natural polymers are efficient to stabilize complex mixtures as a conse-
quence of their high molecular weight, thus inducing large hydrodynamic volumes
for the chains when hydrated in appropriate solvent. Biopolymers (polysaccha-
rides and proteins) do efficiently act as stabilizers due to their ability to induce
steric and electrostatic interactions, change the interface viscosity and viscoelas-
ticity and to increase the continuous phase viscosity thus improving the whole
mixture’s stability. In addition, the interfacial tension may be significantly lowered
by pure proteins and also due to the presence of proteins covalently linked to the
polysaccharide backbone. A recent review focused on pharmaceutical potentiality
of biopolymers brings further details on these crucial properties related to natural
polymers (Bouyer et al. 2012).
In cosmetics, viscosity enhancement and/or weak gel establishment may
be induced by weak interactions and/or chains overlap (e.g. xanthan, starch and
hydroxyethylcellulose), while strong gels may be obtained by intermolecular
complex occurrence (e.g. gelatin, carrageenan and alginate). Depending on the
expected texture level at rest, formulator therefore has a variety of natural poly-
mers and derivatives available when developing a new product. If considering the
whole cosmetic market, the most common natural polymer used is xanthan as it
provides high viscosity enhancement at rest, even at very low concentration, and
remarkable flow properties under shear. Such remarkable viscosity enhancement
and suspending ability is related to the xanthan well-known secondary, semi-rigid,
helix strand conformation. As an example, toothpastes are concentrated disper-
sions, currently owing from 30 to 50 % of abrasive and/or polishing silica particles
and are classically stabilized using xanthan due to its high suspending efficacy.
An interesting illustration is given by examining the rheological data related to
an emulsion formula only differing by the polymer used as stabilizer and texturing
agent (natural or artificial). Gilbert et al. (2012) investigated the effect of polymers
of the whole rheological properties of a given O/W non-commercial emulsion,
specifically developed at lab scale thus only differing by the polymer, most being
natural or artificial, used at a unique level (1 % w/w).
240 G. Savary et al.

100 Viscoelastic plateau limit 1E+1

G’ σ90% G’
90% G’ 1E+0
G’’ G’=G’’
σG’=G’’
G', G'' (Pa)

σ (Pa)
10 1E-1

1E-2

1 1E-3
γG’=G’’
1E-2 1E-1 1E+0 1E+1 1E+2
γ (%) γ90 % G’

Fig. 8.2  An example of viscoelastic data collected within and over the linear viscoelastic pla-
teau. G′, G″ and τ are measured as a function of the strain at 1 rad s−1 (close symbol G′; open
symbol G″; cross oscillatory stress) (Gilbert 2012)

Data are obtained by viscoelastic measurements within and upon the linear
viscoelastic plateau. As represented on Fig. 8.2, it is possible to get different data
referring to the product properties: the elastic and viscous moduli (G′ and G″,
respectively), tan δ or the critical strain and stress, corresponding to the cross-over
point of G′ and G′′ (σG′=G″ and γG′=G″, respectively).
Tested biopolymers, either natural or artificial, cover a wide range of proper-
ties as reported in Table 8.3; data are compared to a “control” emulsion with no
added polymer. The emulsions viscoelastic parameters indicate distinct behav-
iours, ranging from viscoelastic liquids with tan δ close to 1 (e.g. carob, HE cel-
lulose) to weak gel tendency for xanthan containing system (lower tan δ close to
0.1), this latter system being therefore efficient for reaching long-term stability.
In addition, both the viscoelastic plateau limit and the recovery after shear appear
highly dependent from the polymer type thus indicating distinct behaviours when

Table 8.3  Rheological data (means ± SD) obtained from the strain and time sweep tests for
O/W emulsions without polysaccharide (control) and with added polysaccharide
Products G′ (Pa) G″ (Pa) tan δ γG′=G″ (%) τ95% G′ (s)
Carob 58.9 ± 0.0 51.3 ± 0.1 0.870 ± 0.002 7.2 ± 0.2 297 ± 4
Control 84.3 ± 1.6 31.0 ± 0.5 0.368 ± 0.001 38.4 ± 11.2 141 ± 12
HE cellulose 46.6 ± 0.3 36.2 ± 0.4 0.776 ± 0.005 15.2 ± 0.0 264 ± 11
HP guar 56.5 ± 0.9 35.0 ± 0.4 0.619 ± 0.002 40.2 ± 0.1 227 ± 5
HPM Cellulosecellulose 48.6 ± 0.3 27.2 ± 0.4 0.559 ± 0.005 22.5 ± 0.1 257 ± 4
62.6 ± 0.3 17.6 ± 0.1 0.282 ± 0.001 123.8 ± 6.1 182 ± 2
The values of G′, G″ and tan δ correspond to the linear viscoelastic region; τ95% G′ corresponds
Xanthan

to the time necessary for G′ to recover 95  % of its initial value after being submitted to shear
(Gilbert et al. 2013)
8  Cosmetics and Personal Care Products 241

submitted to shear strain. The different emulsions were also characterized using
sensory analysis. Data computation clearly illustrates the key role of polymers on
the whole rheological on a cosmetic emulsion as, more than its lonely stability, it
also directly affects its perception by the consumer.
Moreover, in complex mixture, polysaccharide-surfactant mixtures may lead to
complex formation between both species thus allowing adjusting the rheological
behaviour of the final product (emulsion or non-emulsion systems) to get suitable
texture properties (Lindman et al. 1993). Such association phenomenon is depend-
ing on both the surfactant type (ionic, zwitterionic or nonionic) and the polymer
structure: main backbone, functional groups, pendant species, stiffness, electro-
static properties, hydrophilic/hydrophobic moieties amongst others. Obtaining sta-
bility and expected mechanical properties makes it necessary to consider all these
aspects carefully (Bais et al. 2005). A recent paper interestingly illustrates the dif-
ferent possible effects of protein—polysaccharide association for stabilizing O/W
emulsions; as an example, sodium caseinate-maltodextrin and caseinate-xanthan
combinations are described, showing that polysaccharide cannot simply be consid-
ered as continuous phase viscosity enhancer as it affects droplet network forma-
tion and dynamic, and so the whole mechanical properties (Liang et al. 2014).

8.3.2.4 Controlling End-User Expectations

The key properties of natural and semi-synthetic polymers are unambiguously

their ability, even at low level, to efficiently thicken or gel aqueous media thus
allowing the control of products viscosity at rest, but also when submitted to
mechanical stress during usage. Such mechanical stress may include the pressure
induced by finger during pick-up and spreading over the skin surface, the shear
when spreading varnish over a nail surface using a brush, the pumping of a cream
out of its container and the spraying of a hair fixer. Each of these situations cor-
responds to a specific range of shear intensity; few examples are listed in Fig. 8.3
(Barnes 1994; Brummer and Godersky 1999; Tranchant et al. 2001).
From a general point of view, cosmetic products containing polymer mostly
show non-Newtonian behaviour under shear; this is due to polymer chains coil
deformation and, in the case of emulsions, to the droplet network disruption com-
bined with the ellipsoidal shape adopted by droplets when submitted to shear. In
addition, yield stress parameter is often observed in the presence of polymer. Once

10-2 10-1 100 101 102 103 104 105

Fig. 8.3  Values of shear rate corresponding to different situations when using cosmetics

242 G. Savary et al.

200.00
Carob

150.00 Control
η (Pa.s)

HPM cellulose 100.00

100.00
Xanthan
10.00
50.00

1.00
0.00
0.01 0.1 1 10 100 1000
shear rate (s-1) 0.10
1 10 100 1000

Fig. 8.4  Flow behaviour of O/W emulsions containing without (control) and with various poly-
saccharides: carob, HPM cellulose and xanthan, respectively (from Gilbert et al. 2013a)

the product flowing, the viscosity loss is often over several decades depending on
the conformation and sensitivity to shear of the polymeric specie.
Figure  8.4 gives an interesting illustration of this phenomenon for a series of
emulsions only differing by the thickening agent used, being natural (xanthan,
carob) or artificial (HPM cellulose), compared with the same emulsion with no
added (Control).
As expected, the presence of polymer induces a higher viscosity when com-
pared to the control emulsion with no added polymer. In addition, it is obvious that
viscosity at low shear is higher for the xanthan containing emulsion, while on the
contrary, when submitted to high shear, the emulsions containing carob or HPMC
keep a higher viscosity. Such a dramatic difference makes the products very dif-
ferent for the user as its feeling during emulsion spreading onto the skin appears
“richer” for the latter’s when compared to the control, while spreading the emul-
sion containing xanthan may allow a “lighter” sensation combined with a quicker
product penetration during application. Such a remarkable behaviour is directly
related to the polymer structure, molecular weight and chain conformation. It
allows the formulator optimizing the product performance by judiciously choosing
the polymer, the natural and artificial ones offering the widest versatility.
Texture analysis is a complementary technique which has been intensively
used for many years in the food industry to characterize the mechanical proper-
ties of complex systems; it is a useful tool for analysing the product texture, and is
therefore, more recently, becoming more considerable for cosmetics. Publications
related to texture analysis of cosmetic emulsions were published recently (Roso
and Brinet 2004; Smewing and Jachowicz 2007; Jachowicz and Smewing 2008)
compared to food. Lukic et al. (2012a, b) combined together texture analysis and
rheology to predict W/O emulsions sensory properties.
Gilbert et al. (2013a) described the rheological and texture characterization of
cosmetic emulsions having exactly the same microstructure (identical oil content
and droplet size) but differing for the polymer (either natural, artificial or syn-
thetic) used to modify the aqueous phase rheology; one of the main objectives of
8  Cosmetics and Personal Care Products 243

Fig. 8.5  Penetration curves with the different collected parameters for an emulsion without
(control) or with natural/artificial polymer (from Gilbert et al. 2013a)

this work was to establish relationships between both series of data. Viscometric
and viscoelastic data were obtained through flow, oscillatory and creep methods,
while texture analysis were mainly issued from penetration to compression tests,
with considering various experimental conditions such a probe diameter, speed
and depth or container dimensions. All data were computed to attempt linking
together both categories of physical properties. The results obtained for natural
and artificial polymers interestingly indicate that the different texture parameters
(e.g.: Fmax, see Fig. 8.5) strongly correlate with emulsions viscosity measured
with shear rate varying from 0.1 s−1 to 10 s−1. In addition, harsher operative con-
ditions in compression tests make it possible to correlate texture data to viscosity
measured at much higher shear rate, currently around 1000 s−1. Other interesting
correlations were established with further experimental data: (1) negative area as
recorded with penetration test versus final deformation as obtained through creep-
recovery experiments; (2) compression parameters versus relaxation time after
shear exposure.
Among the various texturing properties characterizing cosmetic products, a par-
ticular sensory attribute related to stretching phenomena is currently considered.
This attribute, expressed as Cohesiveness or Stringiness (Civille and Dus 1991
and 2005; Lee et al. 2005), is evaluated during the pick-up, and corresponds to
the properties perceived in the hand when the product is taken from its container.
Civille and Dus (1991) defined the stringiness as “amount sample deforms or
strings rather than breaks when fingers are separated”. This definition, a bit con-
fused, means that the stringier a product, the more it makes long filaments.
As a mechanical parameter, the sensory evaluation of this attribute is strongly
associated with samples’ extensional properties. Such a filament forming abil-
ity resulting from sudden material’s stretching is depending on many parameters
244 G. Savary et al.

Fig. 8.6  Images of the stretching properties (Lmax) of different emulsions containing different

polymers: control (a), HPM cellulose (b) and HP guar (c) emulsions. Experiments were per-
formed at 40 mm/s, with the P/0.5R probe and a gap of 0.8 mm over 1 cycle (Gilbert et al. 2013c)

related to the product’s composition and structure. Among the other ingredients of
the formulae, polymers of course play a major role due to their well-known elon-
gational properties.
Gilbert et al. (2013c) tested the role of polymers neither natural, artificial or
synthetic, on the stretching properties of a series of emulsions, each different from
another by the polymer used; both sensory assessment and instrumental stretch
experiments were performed and compared together as visible on Fig. 8.6.
The xanthan-based emulsion showed the highest extensional properties, fol-
lowed by the HP guar and HE cellulose emulsions; the carob and the HPM cel-
lulose emulsions presented stretching properties to a lesser extent. Nevertheless,
the aqueous solutions of polymers obtained lower maximum breaking lengths,
especially the xanthan, which suggests that the different ingredients present in
the emulsions could interact together to enhance or attenuate the polysaccharide’s
intrinsic extensional properties.
For ingredients as well as the raw material formulation, the general structural
properties gradually under the action of viscoelastic and capillary forces, con-
tracts, and finally breaks.
The whole data clearly indicate that using natural and artificial polymers when
formulating allows getting emulsion with markedly different shear thinning and
weak gels properties; such versatility is of great interest for formulator when
developing products owning innovative texture.
In addition, it is of primary importance to keep in mind that beside their rheo-
logical modifier function, polymers bring additional benefits for the cosmetic for-
mulations performance; examples are film former, skin hydration, conditioner,
softener, occlusive amongst the other, thus making it real multifunctional ingre-
dients. Numerous examples concern algae for example the microalgal capac-
ity for producing a variety of metabolites such as proteins and carbohydrates
offers a wide variety natural extracts owing thickening properties with additional
interest as active ingredient such as anti-ageing, emollient, anti-irritant, etc.
(Priyadardshani and Rath 2012). Alginic acids, which are polysaccharides isolated
from algae, bring gel properties and also allow water absorption thus preventing
cell collapsing; Agar polysaccharide is efficient as gelling agent, but is also of
interest for cosmetic use due to emollient properties (Wang et al. 2014).
8  Cosmetics and Personal Care Products 245

The growing utilization of polysaccharides and derivatives for cosmetic appli-

cations is clearly linked to such a multiple benefit, as it can be illustrated for poly-
mers issued from biotechnology.

8.3.3 Impact on the Properties During Application

A cosmetic product is attractive for consumer use as a result of its function, its
promise of efficiency but also the pleasure it brings to them. The cosmetic prod-
ucts are intended for contacting the superficial parts of the body, or with the teeth
and mucous membranes. During application, consumers have a primary expecta-
tion which could be for example moisturizing the skin with a cream, washing the
hair with a shampoo, protection against UV with a sunscreen, colouring and pro-
tection of nails with a varnish and secondary expectations such as a non-sticky
face cream, a shampoo easy to spread on the hair or a varnish simple to apply on
the nails.
As showed in the previous paragraph, polymers made possible to monitor the
rheological behaviours of cosmetics. This will largely affect the properties during
the handling of the product, during its use and after application. Among polymers,
some are used only to modify the intrinsic properties of the cosmetic product
(such as its appearance, consistency, firmness and spreading on the skin or the
hair). Others are used for their ability to form a film at the surface of the skin,
the nails or the hair. These film-forming polymers are added in hair fixatives or in
varnish and give a protection against dehydration and against chemicals and pol-
lutants from environment.
Furthermore, polymers may be used as active, moisturizer, hydrating agent or
conditioners. In this case, the polymer (mostly hydrolyzed) is able to penetrate tis-
sues and to bring a beneficial action at the cellular level, such as water-retention
into the skin, reconstruction of the damaged tissues and stimulation of the produc-
tion of key elements amongst other properties.

8.3.3.1 Impact of Polymers on the Sensory Properties

The evaluation of these properties before, during and after application uses
directly human persons either through sensory evaluations or through clinical
trials.
The sensory evaluation is a measuring instrument of the sensations perceived
by a consumer when applying a cosmetic product. For that, a “panel”—a group
of assessors—is used with specificities according to the objective of the study and
to the test to be carried out. The sensory evaluation gathers together different tests
that use the five human senses to evaluate the properties of a product: sight, hear-
ing, touch, taste and smell.
246 G. Savary et al.

The sensory evaluation was developed at first in the food field and that made
possible to establish standardized test conditions that are nowadays available for
the cosmetic field. It is necessary to make a distinction between, on the one hand,
the hedonic tests that are performed to evaluate the personal appreciation of a
product by consumers. These tests are carried out by questioning a large panel of
“naïve” assessors that are among the potential targets for the cosmetic product.
Tests may also be made directly at home. On the other hand, discriminative and
descriptive tests are performed to analyse and characterize the cosmetic products
with more experienced assessors or even with experts. Such tests are realized in a
sensory laboratory and often require several evaluation weeks. Products are evalu-
ated directly in the container, during application onto the skin, the nails, or the
hair; in addition, hair care products are often tested using hair tresses.
In the cosmetic field, the five human senses are involved in the perception of
the product. The sense of smell is of course essential to evaluate the perfume of
a cream or soap and is a key element for the emotional point of view. The sight
makes possible to evaluate the colour of a make-up, a hair colouring, the gloss
attribute of a cream, etc. The sense of hearing is secondary in cosmetic, whereas
the sense of taste concerns only the products which are in contact with the oral
mucosa (toothpaste, mouthwash, lipstick, gloss, etc.). The sense of touch is par-
ticularly important in cosmetic; it is involved in the perception of the somatic sen-
sations including several modalities such as pressure, skin stretch, vibration, pain
and temperature perceived by many receptors and mechanoreceptors localized at
various depth in the skin and the mucous membranes.
Polymers are commonly named texturing agents because they fully contribute
to the texture of the products; this parameter is a complex and multidimensional
parameter. The procedure for the sensory evaluation of the texture is generally
split in four categories, namely “appearance”, “pick-up”, “rub-out” and “residual
appearance and after feel”. However, the influence of natural polymers on sensory
skin feel properties for cosmetic products has been very little investigated. Gilbert
et al. (2012) were interested in the impact of polymers on the texture properties of
cosmetic creams. The study focused on eight hydrophilic polymers, either natural
(xanthan and caroub), derivate (hydroxy ethyl cellulose, hydroxyl propyl guar and
hydroxyl propyl methyl cellulose) or synthetic (carbomer, polyacrylamide, and
ammonium acryloyldimethyltaurate/VP copolymer). Polymers were incorporated
at a concentration of 1 % w/w in an O/W emulsion and a formulation without
any polymer was also prepared. The contribution of each polymer to the sen-
sory properties was investigated using the Spectrum Descriptive Analysis (SDA)
method. In order to properly discriminate the texture properties of the nine emul-
sions, eight attributes were selected: Gloss and Integrity of shape evaluated during
the first phase, named “appearance”; Penetration Force, Compression Force and
Stringiness evaluated during the “pick-up”; Difficulty of spreading and Absorbency
evaluated during the “rub-out” and Stickiness evaluated in the last phase, named
“residual appearance”. Results highlighted significant differences between the tex-
ture of creams according to the polymer used and its origin (see Fig. 8.7).
8  Cosmetics and Personal Care Products 247

Fig. 8.7  Results of the sensory characterization of cosmetic O/W emulsions containing different

polymers at 1 % w/w: xanthan, caroub, hydroxy ethyl cellulose (HE cellulose), hydroxyl propyl
guar (HP guar), hydroxyl propyl methyl cellulose (HPM cellulose), laureth-7, C13-14 isoparaf-
fin, polyacrylamide (PA), carbomer (PAA) and ammonium acryloyldimethyltaurate/VP copoly-
mer (AADMT-co-VP). The “Control” emulsion was prepared without polymer. The results of
PCA: loading plot of the attributes (a) and of emulsions (b) (Gilbert et al. 2012)

The emulsions with synthetic polymers exhibited a higher firmness and consist-
ency than those with natural or modified polymers. Otherwise, emulsions contain-
ing natural polymers showed better spreading properties on the skin, which is an
important criterion during application. It is noteworthy that natural and modified
polymers confer also stringiness during pick-up and stickiness feeling after appli-
cation of the cream to the skin.
As a consequence, natural polymers are not the more appropriate ingredient to
modify the lonely consistency and the firmness of cosmetic creams when compare
to the synthetic polymers. For this reason, natural polymers are often associated
with synthetic ones in order to control properties during application as for instance
the spreading performance of the product during use (see example of formulation
in Sect. 8.4: body lotion with 0.2 % of carbomer and 0.1 % of xanthan).
The sensory evaluation also concerns the hair care product. Derivates from
natural polysaccharides are for example widely included into hair conditioners to
achieve sensory improvement. Hair conditioners are generally used after sham-
pooing the hair by taking a small portion on the palm, applying on the wet hair,
spreading, rinsing, wiping with a towel and drying with a blower. It is commonly
admitted that the feel during application can be improved with polymers such as
polyquaternium-10 or hydroxyl ethyl cellulose (Lochhead 2007). Nevertheless,
such results remain largely unpublished.
Natural polymers are used in cosmetic products as texturing agent but some of
them are also able to protect or penetrate tissues and are used as active ingredients,
film formers, moisturizers, hydrating agents or conditioners. This is discussed in
the following sections.
248 G. Savary et al.

8.3.3.2 Polysaccharides Used as Conditioning Agents and Active

Ingredients

Compounds that can improve the skin or hair surface are so-called conditioning
agents. The mechanisms by which conditioning compounds do this vary depend-
ing on the type of compound and surface to which they are applied to. One of the
primary methods by which conditioning ingredients act consists on regulating the
amount of moisture of skin or hair (Gesslein 1999).
The skin consists of epidermis, the most exposed part, directly in contact with
the external environment. It is assembled by multiple superposed cell layers that
form an effective protection barrier. Over the years, however, epidermal primary
functions may gradually falter. Molecular, cell-related, and morphological changes
in aged epidermis not only compromise its protective role, but also contribute to
the appearance of skin symptoms as for example excessive dryness, formation of
wrinkles and skin irritation. The possible therapeutic strategies include the use of
moisturizing compounds and the application of active ingredients able to stimulate
biological responses or to reactivate biological pathways. Among the active ingre-
dients, some polymers are used in cosmetic formulations.
Different polysaccharides are notably added to skin care products because of
their water-retention properties that contribute to the epidermis hydration. As an
example, that is the case of chitosan that is a natural polymer abundantly found in
crustaceans obtained by deacethylation of chitin. Chitosan is used as thickening
and gelling agent and as active since its water-retention properties are also effi-
cient to maintain skin moisture. Chitosan has also attracted the attention owing
antimicrobial activity in oral care (toothpaste), peculiar biological properties in
wound healing and specific characteristics for applications in hair care. As the
only cationic polysaccharide in nature, chitosan in aqueous solutions interacts with
negatively charged damaged hair via electrostatic interactions. It forms a film that
improves suppleness of hair and reduces static electricity. However, chitosan is
normally insoluble in aqueous solution above pH 7 because of the stable, crys-
talline structure. To improve the solubility of chitosan and exploit its application,
different methods of chemical modification (PEG-grafting, hydroxylation, sulfona-
tion, quaternization and carboxymethylation) are commonly applied (Rinaudo
2006).
Polysaccharides used as active also include hyaluronic acid (HA). HA is a gly-
cosaminoglycan (GAG) widely distributed throughout the dermis and the epider-
mis. HA is synthesized by skin fibroblasts and is involved in the tissue repair and
in skin’s moisture balance due to its high performance in water-retention. HA can
absorb water about 1000 times its own volume. Nowadays it is mainly obtained by
biotechnology and is used as active ingredient in topical applications for skin care
including anti-ageing products. It is often used as a sodium salt (sodium hyaluro-
nate) or hydrolyzed forms owing various molecular weights. As HA is naturally
found in the dermis, its biocompatibility with skin is a key point. According to its
molecular weight, HA forms an elastic and permeable film on the surface of the
8  Cosmetics and Personal Care Products 249

skin or penetrates the stratum corneum and may act in skin renewal (Bourguignon
et al. 2013; Lorencini et al. 2014).
Other natural polysaccharides are used as active ingredients in cosmetics. Wang
et al. (2014) indicate for example that polysaccharides from marine algae may act
as hair conditioners and wound-healing agents, and can also moisturize, hydrate
and emolliate. Several yeasts and yeast-like fungi are also known to produce
extracellular polysaccharides. Most of these contain d-mannose, either alone or in
combination with other sugars and phosphate. Almost all of the yeast exopolysac-
charides are known to display some sort of biological activity and some of them
already find applications in cosmetics as moisturizer (Van Bogaert et al. 2009).
Exopolysaccharides may also be obtained by bacterial fermentation and display
protective effects against pollution, heavy metals and ultra violet light. The case of
exopolysaccharides produced by marine microorganisms is also detailed in the lit-
erature Finore et al. (2014), as well as the possible applications of such polymers
as GAG-like molecules to replace hyaluronic acid or heparin (Delbarre-Lachat
et al. 2014).

8.3.3.3 Proteins Used as Conditioning Agents and Active Ingredients

Proteins are widely used in skin care and hair care products as moisturizing
agents, film formers and also used for their ability to repair skin tissues. Widely
used proteins include collagen, keratin, silk protein and soybean protein. There
are hydrolyzed products of these proteins of various molecular weights. Molecular
weight primarily determines a number of properties of hydrolyzates. The molec-
ular weights cited for hydrolyzates represent average values for relatively broad
distribution. Thus, a range of 1000–5000 Da for hydrolyzate may be considered
“narrow”. Humectancy (hygroscopicity) is greatest for individual amino acids,
which can absorb several times their weight in water. Therefore, humectancy per-
formance diminishes exponentially as the size of the polypeptide increases, while
non occlusive protective colloidal film-forming properties concurrently increase.
Concerning hair conditioning, substantial quantities of at least some hydrolyzates
penetrated through the cuticle into the cortex. The amount of hydrolyzate bound
increased markedly with increasing damage (virgin < bleached ≪ bleached and
waved). Evaluation of hydrolyzates applied to human skin revealed that penetra-
tion was limited to the outer layers of the stratum corneum; consequently, hydro-
lyzates mainly function as film formers and moisturizers (Neudahl 1999).
As an example, collagen is naturally present in connective skin tissues; there-
fore, collagen hydrolyzates are currently used in cosmetic formulations for proper-
ties such as skin structure and function protecting, thus enhancing its appearance.
Collagen is unique in its ability to form insoluble fibres that have a high tensile
strength and right-handed triple super helical rod consisting of three polypeptide
chains. Collagen has been, traditionally, isolated from the skins of land-based
animals, such as cow and pig. Collagen is usually incorporated into hydrating
cream at 1 %. However, in recent years, the uses of collagen and collagen-derived
250 G. Savary et al.

products of land animal origin have become of more concern. As a consequence,

alternative sources of collagen especially from aquatic animals including freshwa-
ter and marine fish and molluscs have received increasing attention (Veeruraj et al.
2013).
Another interesting example is keratin, a highly specialized intracellular epi-
dermal protein. It comprises the main bulk of the horny layer of the skin, and
with modification forms specialized structures such as hair or nails. Keratin is
a fibrous film-forming protein used in hair and skin care products. It is thought
to bring different benefits to hair and skin, such as linking to structural proteins,
restoring the surface damages, enhancing the surface moisture content, and sur-
face coating. Water-soluble hydrolyzed keratin, often derived from sheep’s
wool, is a cosmetic active and consists in peptides of about 10–20 amino acids.
Cocodimoniumhydroxypropyl hydrolyzed keratin is a hydrolysed keratin which
has been modified with a quaternary ammonium group. This truly cationic pol-
ymer is found in various hair care products in which it prevents damages and
repairs the hair. Hair mainly consists in keratin and can be more generally repaired
from damage by supplying proteins. Proteins are included in hair condition-
ers to that purpose. Since many years, protein derivatives have been developed
to improve molecular binding with hair; examples are cationated, acylated, and
silylated proteins (Bolduc and Shapiro 2001).
Small peptide fragments are also common components of anti-ageing topical
formulations. They penetrate through the skin epidermal layer and may be able
to induce synthesis of dermal extracellular matrix, thus restoring damaged tissues.
Many are thought to act as ‘matrikines’, a concept that peptide fragments pro-
duced naturally during extracellular matrix protein processing—most commonly
collagen or elastin processing—can act as signalling intermediates, thus simulat-
ing cells to increase extracellular matrix production. Bradley et al. (2015) present
a review of the various peptide fragments, mainly consisting on tetra-, penta- and
hexapeptide used to repair photo-aged skins.
Finally, it should be noted that protein products are generally used as active and
they have almost no influence on the sensory characteristics of cosmetic products
because the current amount used in the cosmetic formulae remains fairly small.

8.4 Examples of Cosmetic Formulations Including

Polymers

Natural and artificial polymers are commonly used in a large range of cosmetic
products. They appear among the minority ingredients with amount below 1 %
wt but are indispensable to satisfy requirements in term of stability, rheologi-
cal behaviours, sensory and active properties. Generally, only one polymer is
not enough and a mix of different polymers is required. Most of the time, natu-
ral polymers are found as powder but are sometime commercialised as a liquid
8  Cosmetics and Personal Care Products 251

form (aqueous solutions at 1 or 2 % including preservatives). Natural polymers

are mainly hydrocolloids and their dissolution in the solvent medium is one of the
critical steps in the preparation procedure. That is the reason why the polymer is
usually added alone as a separated phase by following specific conditions in term
of stirring, time or temperature. In the cosmetic field, the cold water-soluble poly-
mers are preferred in order to avoid heat treatment during processing. However,
heating speeds up the dissolution and is sometime obliged to hydrate certain natu-
ral polymers, highly ordered or with an important crystalline phase, as for instance
locust bean gum (temperature required around 80 °C). Always in order to facilitate
dissolution, it is possible to prepare a premix of the polymer powder with the other
dry ingredients or to pre-disperse it in a non-solvent medium (oil, alcohol, polyols,
etc.). Dissolution depends on the product in which the material is being used and/
or the type of equipment available.
Below are given several examples of cosmetic products quantitative formula
including natural and artificial polymers. General information and preparation pro-
cedure are given for each example. The role of natural polymers and derivatives is
explained. See the book Personal Care Formulas (2006) for more formula.

8.4.1 Skin Cleansers

Body cleanser and shower gel, also known as bodywash, is liquid soap used for
cleaning the body. It is a water-based product with high detergent concentration
(e.g. sodium lauryl sulfate, ammonium laurethsulfate, Triethanolaminecocoyl glu-
tamate) used as a skin cleansing agent in the shower or bath. If compared to clas-
sical soap, it is less irritating to the skin, lathers better even in case of hard water
and does not leave a mineral residue on the skin after usage. Thickening water
solution polymer (e.g. Hydroxyethyl cellulose) is added to reach suitable viscosity.
It may contain ingredients with a long-lasting cooling and stimulating sensation on
the skin (e.g. menthol, menthyl lactate), and it is often designed for hair and body
combined utilization. Shower gels contain milder surfactant bases than shampoos
and in addition to being pH-friendly to the skin, most are also prepared with gentle
conditioning agents. Conditioning polymers are polycations (e.g. Guar hydroxy-
propyltrimonium chloride) as keratin substrates (especially hair) carry a net nega-
tive charge, thus involving strong surface-product interactions. This formulation
has strong foaming power and very low skin irritation. It also leads to moisturiza-
tion and silky after-feel (Table 8.4).

8.4.2 Hair Cleanser and Hair Conditioner

A shampoo is a cosmetic care product that is used for cleaning hair. The goal of
using shampoo is to remove the unwanted build-up without stripping out so much
252 G. Savary et al.

Table 8.4  Composition of a cooling shower gel (Sino Lion) from Personal Care Formulas
(2006)
Phase INCI name wt%
A Water (Aqua) Qsp 100.00
Hydroxyethyl cellulose 0.80
B Disodium EDTA 1.00
Ammonium laurethsulphate, 25 % 28.00
Triethanolaminecocoyl glutamate 20.00
C Guar hydroxypropyltrimonium chloride 0.30
Lauramide MEA 2.00
Menthyl lactate 0.30
Saffloweramide DEA (and) isostearamide DEA 0.50
Sodium isostearyllactylate 0.50
DMDM hydantoin (and) IPBC 0.30
D Citricacid, 20 %, to pH 6.50 Qs
Fragrance (parfum) Qs
Sodium Chloride, 20 % Qs
E Styrene/acrylates copolymers 0.80
Procedure Heat part of water* to 50 °C and add hydroxy ethyl cellulose; mix until dissolved.
Add disodium EDTA and agitate for 5 min. Add the remaining B ingredients with agitation. Heat
up to 70 °C. Add C and mix until uniform. Premix E with 4 times amount of water and add into
the vessel, mix for 15 min
*Reserve amount necessary for addition of E
Bold corresponds to the polymers used in the list of ingredients.

sebum thus leaving hairs unmanageable. Shampoo is generally made by com-

bining surfactant(s) (e.g. ammonium lauryl sulfate, ammonium laurethsulfate,
cocoamidopropylbetain) in water to form a thick, viscous liquid. Other essential
ingredients include salt (sodium chloride) used to adjust the viscosity by micel-
lar mechanism and polymers as thickening agents (e.g. xanthan gum). Substantive
conditioning properties may be controlled by using appropriate polymeric ingre-
dients (e.g. polyquaternium-10, Hydrolysed wheat protein PG-propyl silanetriol).
Preservatives and fragrance are also added. Many parameters such as foam forma-
tion and stability, skin and eye irritation, hair protection or damage repair, biodeg-
radability, etc., have to be considered when developing the product (Table 8.5).
The basic formula of hair conditioners is fairly similar to shampoo. The con-
ditioning mechanisms can be various, but require ingredients to bind with hair
keratin thus inducing resistance to rinse and mechanical strain. Different kinds of
interactions may be involved, but electrostatic are the main ones. Examples are
cationic polymers (such as quaternized cellulose or guar gums), protein and pro-
tein hydrolysates (issued from, e.g. corn, milk, silk, soy, wheat and yeast) all being
commonly used as cosmetic ingredients with conditioning properties (Table 8.6).
8  Cosmetics and Personal Care Products 253

Table 8.5  Composition of a Moisturizing Shampoo (Stepan) from Personal Care Formulas

(2006)
Phase INCI name wt%
A Water (Aqua), deionized Qsp 100.00
B Polyquaternium-10 0.30
C Xanthan gum 0.50
D Disodium EDTA
Ammonium lauryl sulphate 25.00
Ammonium laurethsulphate 18.00
Cocamidopropylbetain 3.60
PEG5-cocamide 0.50
Sodium laurethsulfate (and) ethylene glycol distearate (and) cocamide 3.00
MEA
Glycol stearate 0.75
Dimethiconecopolyol 1.00
E Polyquaternium-7 3.00
Panthenol 0.15
Fragrance (parfum) Qs
Dye Qs
Preservative Qs
F Citric acid Qs
G Sodium Chloride Qs
Procedure In a suitable vessel equipped with heating and agitation capabilities, Charge A.
Sprinkle B into A. Mix until well dispersed. Sprinkle C into AB. Mix until well dispersed and
heat at 72–75 °C. Add D under moderate agitation. Keep heating at 72–75 °C, and mix for at
least 30 min until completely dissolved. Cool to 40 °C with adjusting mixing speed to avoid min-
imize aeration. At 40 °C, add E and continue mixing. Cool to 25 °C. Adjust pH with F, if neces-
sary. Adjust viscosity with G, if necessary
Bold corresponds to the polymers used in the list of ingredients.

8.4.3 Skin Care

Skin care products are used to improve the skin appearance and health, formulated
for different types of skin: normal, dry or oily. Skin care products include cleans-
ers, facial masks, moisturizers, sunscreen, tanning oils and lotions, skin lighteners,
serums, etc. Most skin care products are O/W emulsions. Normal skin is neither
greasy nor dry, and usually appears clear with no spots or blemishes, and therefore
requires gentle treatment. Such a skin requires common maintenance. Dry skin
tends to flake easily due to its no efficacy to retain moisture and insufficient pro-
duction of sebum by sebaceous glands. In that case, using a moisturizer for both
day and night creams may be essential. Finally, oily skin is more or less greasy,
which is caused by the over secretion of sebum. The excess oil on the surface of
254 G. Savary et al.

Table 8.6  Composition of a thermal protection hair conditioner from Personal Care Formulas

(2006)
Phase INCI Name wt%
A Water (Aqua) Qs 100.00
B Hydroxyethyl cellulose 0.30
C Quaternium-82 1.00
Cetrimoniumchloride 3.33
D Cetyl alcohol 1.50
Stearyl alcohol 2.00
Pentaerythrityltetracaprylate/tetracaprate 2.50
Phenyl trimethicone 0.50
E Wheat amino acids 1.00
Hydrolized wheat protein PG-propyl silanetriol 1.00
F Sodium hydroxide Qs
G Citric acid Qs
H Preservative, colour, fragrance (Parfum) Qs
Procedure Disperse B into A. Add F to raise pH to 7.0–8.0. When solution is clear, adjust pH
with G to a pH of 4.0–5.0. Add C and mix well. Start heating to 76–82 °C. Add D at 77 °C. Mix
well for 20 min. Start cooling to room temperature. Add E at 38 °C. Mix well. Add F or G, if
necessary, to adjust pH. Add H. Mix well
Bold corresponds to the polymers used in the list of ingredients.

the skin causes dirt and adhesion of dust from the environment. Consequently, it
needs to be cleansed thoroughly every day; moisturizing with an oil-free, water-
based and non-comedogenic moisturizer is required, and efficient exfoliation may
be necessary so to improve the skin’s appearance. In all cases, the texture of skin
care products is of primary importance, thus requiring viscosity adjustment by
hydrocolloids for reaching suitable viscosity and improving the systems stabil-
ity (e.g.: xanthan gum, cellulose ether). Further functional properties such as skin
adhesion of mask may be obtained by adding colloids (e.g. Acacia gum). Below
are examples of two O/W emulsions, obtained by hot and cold process, respec-
tively (Tables 8.7 and 8.8).

8.4.4 Toothpaste

Toothpaste is a semi-solid product (often paste) designed to clean teeth and leave
breath smelling and feeling fresh. The primary function of toothpaste is to remove
debris from the teeth surface. It has to be easily extruded from its tube, to keep
stiff enough to remain on the toothbrush and have a consumer acceptable taste.
Toothpastes are a blend of surfactants, abrasives (e.g. hydrated silica), water,
humectants, anti-caries actives, thickening agents (e.g. xanthan gum, cellulose
gums and carrageenan), flavouring, and other aesthetic ingredients. Mechanical
8  Cosmetics and Personal Care Products 255

Table 8.7  Composition of a Moisturizing Facial cream with sunscreen from Personal Care

Formulas (2006)
Phase INCI Name wt%
A Water (aqua), dionized Qs 100.00
B Xanthan gum 0.17
C Propylene glycol 0.75
Glycerin 1.25
Aloe barbadensis gel 0.50
Sodium PCA 0.25
Preservative 0.10
D Petrolatum 3.50
Octylmethoxycinnamate 5.25
Meadowfoam seed (Limnathes alba) oil 1.75
Oxybenzone 2.35
Octyl salicylate 1.50
Neopentylglycoldicaprylate/dicaprate 2.30
Glyceryl stearate 1.50
PEG-150 distearate 1.75
Stearic acid, triple press 1.25
Emulsifying wax, NF 0.50
Cetyl alcohol 0.50
E Cellulose ethers, 2 % soln 16.50
F Water (aqua), deionized 1.00
Imidazolidinyl urea 0.25
G Citric acid, 50 % soln Qs
Procedure Heat A to 60 °C under propeller mixing at medium speed. Add B slowly, continue
mixing until completely in solution and hydrated, approximately 10 min. Premix C and add to
batch. Pre-blend D and heat to 65–70 °C under propeller mixing until completely clear. Then add
D to batch on a Homomixer at medium speed for 2 min. Premix/prepare E. Heat to 55 °C with
mixing. Add to batch on Homomixer at medium speed for 2 min. Reduce speed on Homomixer
to low setting and cool to 40–45 °C. Place on mixer using sweep blade at low speed, cooling to
35 °C. Premix F and add to batch at 35 °C. Then cool to 25 °C, adjust pH, if necessary, with G
Bold corresponds to the polymers used in the list of ingredients.

action of abrasive agents allows stain removal; the large proportion of particles
makes it necessary to use efficient suspending agent to stabilize the mixture (Table
8.9).
256 G. Savary et al.

Table 8.8  Composition of a 0/W PEG-free body lotion, cold processing from Personal Care
Formulas (2006)
Phase INCI Name wt%
A Sorbitanoleate (and) polyglyceryl-10 laurate 2.00
Isononyl stearate 2.50
Isopropyl palmitate 6.00
Avocado (perseagratissima) oil 5.00
Jojoba (Simmondsiachinensis) oil 2.50
B Water (Aqua) 40.00
Carbomer 0.20
Xanthan gum 0.10
C Water (Aqua) Qs 100.00
Glycerin 3.00
Water (and) propylene glycol (and) Acacia senegal 8.00
D Triethanolamine, 99 % pH 6.00–6.50
E Tocopherol 0.05
Tocopheryl acetate 0.20
Fragrance (Parfum) Qs
Preservative Qs
Procedure Premix A, B and C separately to obtain homogeneous phases. Add C to B while stirring.
Add A to BC. Homogenize for 2 min. Add D and E while stirring
Bold corresponds to the polymers used in the list of ingredients.

Table 8.9  Composition of a toothpaste product

Phase INCI Name wt%
A Water Qs 100.00
Sodium benzoate 0.60
ChlorhexidineDigluconate 0.05
Sodium Saccharin 0.08
Sodium Monofluorophosphate 0.76
Glycerin 10.00
Sorbitol 10.00
B Xanthan gum 0.80
Cellulose gum 0.30
C Tetrasodium Pyrophosphate 1.00
D TitaniumDioxide 0.30
HydratedSilica 30.00
E Sodium Lauryl Sulphate 29 % 1.50
F Fragrance (Parfum) 0.50
Procedure Mix Phase A ingredients together. Gently add Phase B under vigorous stirring, keep
stirring until complete powders dispersion. Gently add Phase C until complete dissolution. Phase
D: Slowly add Titanium dioxide/half of hydrated silica quantity premix to previous mix. Append
the rest of Phase D to the mixture once the mixture homogeneous. Mix under vacuum using high
speed rotor–stator for 15 min. If necessary, keep stirring to reach complete homogenization. Poor
Phase E under vacuum using gentle stirring and then add phase F
Bold corresponds to the polymers used in the list of ingredients.
8  Cosmetics and Personal Care Products 257

8.5 Conclusions

As illustrated in this chapter, natural polymers are commonly used in any kind of
cosmetic products; the utilization of proteins, polysaccharides and corresponding
derivatives in the cosmetic industry is due to their wide range of properties such as
stabilizer, texturing agent, hydrating, film former and sensory ingredient. A vari-
ety of natural and artificial polymeric raw material is nowadays available, and the
interest for such ingredients is growing year after year due to several reasons:
• The good image of natural ingredients by consumers makes it of great interest
from a marketing point of view;
• The ability for natural polymers to significantly increase the dispersions
stability;
• The wide variety of textures available, ranging from low viscous to highly
gelled systems;
• The development of “eco-labels” and “natural cosmetics” requires relevant sub-
stitution of synthetic raw materials;
• The Life Cycle Assessment (LCA) requires considerations such as biodegrada-
bility and/or low Carbon Footprint;
• The general biocompatibility requirements with skin and mucus is much better
with natural ingredients;
• Natural “active” ingredients allow improving product efficacy;
• The reaching of higher aesthetic and sensory performance;
Consumer may decide to buy a product on the basis of a complex compromise
between sensory expectations and allegations (e.g. ease of pick-up, pleasure dur-
ing application, skin softness and multifunctional), efficacy (e.g. anti-ageing, hair
conditioning, make-up resistance to water and sunscreen protection), specific
requirements (e.g. natural or “bio” products and anti-allergenic) and, of course
economic considerations.
Natural cosmetic ingredients market in Western Europe is estimated to cross
$800 million in 2017, while it was $6592 million in 2012 (Source: Frost and
Sullivan, January 2014). For all these reasons, like in other domains, the cosmetic
industry requires constant innovation, and is permanently searching for new ingre-
dients or technologies; among the other natural ingredients categories, research for
new developments of natural polymers is very active, with a market growing rap-
idly over the world. Few examples are given in the following perspectives.

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Chapter 9
Pharmaceutical Applications of Natural
Polymers

Atul Nayak, Ololade Olatunji, Diganta Bhusan Das

and Goran Vladisavljević

List of Abbreviations

API Active pharmaceutical ingredients

BTCA Butanetetracarboxylic dianhydride
CMC Carboxymethyl cellulose
CNS Central nervous system
DB DamarBatu
DMAP 4-dimethylaminopyridine
HGH Human growth hormone
HPMC Hydroxypropylmethyl cellulose
Lo Lecithin organogel
NaCMC Sodium carboxy methyl cellulose
N-IPAAm  N-isopropylacrylamide (NIPAAm)
pAA Polyacrylic acid
PEG Polyethylene glycol
PELA, PLA Polylactic acid
PLGA Poly(dl-lactic-co-glycolic acid)
PLLA Poly(l-lactic acid)

A. Nayak · D. Bhusan Das · G. Vladisavljević 

Department of Chemical Engineering, Loughborough University,
Loughborough, Leicestershire, UK
O. Olatunji (*) 
Chemical Engineering Department, University of Lagos,
Akoka, Lagos, Nigeria
e-mail: lolakinola@gmail.com

© Springer International Publishing Switzerland 2016 263

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_9
264 A. Nayak et al.

PSA Pressure sensitive adhesives

PVA Polyvinyl alcohol
SPG Shirasu porous glass
TDD Transdermal drug delivery

9.1 Introduction

Natural polymers have a very broad range of applications in both the polymer
and pharmaceutical industries. The pharmaceutical industry is a very broad field
where there is a continued need to consider various applications. It is logical,
therefore, to state that understanding the roles of natural polymers in the phar-
maceutical industry helps in turn the polymer industry to determine the broader
applications of these polymers and incorporate the desired requirements to meet
the end applications (e.g. provide various functionalities). Drug delivery methods
form a key part of the pharmaceutical applications of polymers. In the next sec-
tion of this chapter, we discuss portals of drug administration into the human body
which gives an overview of the possibilities of applications of natural polymers.
The chapter then discusses some specific applications in detail. Transdermal drug
delivery, nasal drug delivery, vaginal, ocular, oral drug delivery methods using nat-
ural polymers are discussed with some example case studies. As hydrogels play
important roles in drug delivery, a separate section is dedicated in discussing the
applications of natural polymer-based hydrogels in drug delivery.

9.2 Portals of Drug Administration in the Human Body

The controlled delivery of drug molecules requires either a device or a vehicle for
administration into specific localised tissues or systemic distribution via plasma
fluid in blood. The human body has several portal entries for drug administration
as outlined in Fig. 9.1. These portals are intramuscular (Suh et al. 2014), percuta-
neous (Ge et al. 2014), intrathecal (Freeman et al. 2013), subcutaneous (Kinnunen
and Mrsny 2014), gastrointestinal (Varum et al. 2013), ocular (Mignani et al.
2013), intravenous (Mignani et al. 2013), nasal (Tian et al. 2014), pulmonary
(Beck-Broichsitter et al. 2012), sublingual (Patel et al. 2014), baccal (Patel et al.
2014), rectal (Lautenschläger et al. 2014) and vaginal (Valenta 2005). Intravenous,
intramuscular, percutaneous, intrathecal, subcutaneous and transdermal are col-
lective terminologies associated with parenteral administration. Pulmonary drug
administration through the lungs is the least common portal delivery because of a
limited number of excipients, especially natural polymeric excipients with reduced
polydispersity of size and ideal particle densities concerning the drug particle for-
mulation (Sanders 1990; Pilcer and Amighi 2010).
9  Pharmaceutical Applications of Natural Polymers 265

Fig. 9.1  An outline of main portals for drug administration (Adopted from www.themednote.
com with permission)

9.3 Transdermal Drug Delivery Devices

Polymers are used extensively in transdermal drug delivery systems. They control
the rate of drug release from the device, act as primary packaging parts, coatings,
penetration enhancers and provide ease in drug device handling and structural sup-
port to the device in the form of a backing layer. Their unique properties make
them ubiquitous component of transdermal patches. As petrochemical-based
resources for the production of synthetic polymers become more expensive and
in short supply, the production of transdermal drug delivery device components
from more readily available natural polymers becomes eminent. This section of
the review looks at the application of natural polymers in transdermal drug deliv-
ery. The different parts of the transdermal drug delivery system are discussed such
that the use of natural polymers in each individual part, namely, the matrix, adhe-
sive layer, rate controlling membrane, backing layer, release liner and penetration
enhancer are then discussed. Further areas to be explored are also suggested.
Polymers are used more extensively in transdermal drug delivery (TDD) than
any other material as they possess unique properties which are significant to the
drug delivery process (Kim 1996). They are effective in aiding the control of
drug release from carrier formulations (Cleary 1993). Polymers commonly used
in TDD include cellulose derivatives, polyvinylalcohol, chitosan, polyacrylates,
polyesters such as PLGA, PELA, and PLA and silicones. Natural polymers are
a preferable option in TDD as they are readily available, inexpensive, potentially
biodegradable and biocompatible and can undergo various chemical and surface
modifications to fit the requirement of the TDD system. A TDD system comprises
266 A. Nayak et al.

of a combination of one or more polymers and an embedded drug to be delivered

into or through the skin in a controlled and sustained manner (Tojo 2005).
Polymers used for TDD systems are required to be chemically inert and pure
according to high analytical product yields. It should also possess adequate physi-
cal properties which correspond with the intended application. The material must
not age easily and be suitable for processing. Furthermore, biodegradability and
safety are paramount properties in the design of a TDD patch system due to the
long-term exposure of the skin in contact with the patch (Pietrzak et al. 1997).
This section focuses on the application of natural polymers in transdermal
drug delivery. The next subsections discuss the different types of transdermal drug
delivery systems explaining each one is separate subsection. Section 9.3.2 dis-
cusses the use of polymers in transdermal drug delivery with specific focus on nat-
ural polymers. Within the section the different parts of a transdermal drug delivery
system are discussed. The properties and function of each is first described and
some recent studies of developing natural polymers in the specific area are then
outlined.

9.3.1 Types of Transdermal Drug Delivery Systems

TDD systems are classified into three types, namely, reservoir, matrix and micro-
reservior system (Kandavilli et al. 2002; Chein 1987). Each of these is described
below.

9.3.1.1 Reservoir System

The reservoir system comprises of a reservoir of drug in the form of a suspension,

solution or liquid gel embedded between an impervious backing layer and a rate
controlling membrane. Suspensions and solutions are two distinct types of liquid
mixtures. The definition of a suspension and a solution is well understood. The
definition of a liquid gel can sometimes be difficult to formally express. A gel is a
semi-solid, colloidal solution consisting of one or more crosslinked polymers dis-
persed in a liquid medium. A liquid gel is softer, less resilient and easily spread-
able colloid gel. The reservoir could also be the drug dispersed within a solid
polymer matrix. An adhesive polymer is often placed between the rate controlling
membrane and the skin.

9.3.1.2 Matrix System

The matrix system comprises of drug molecules dispersed within a polymer matrix.
The matrix system is of two types, the drug in adhesive system and the matrix-dis-
persed system. In the drug in adhesive system, the drug is dispersed in a polymer
9  Pharmaceutical Applications of Natural Polymers 267

adhesive. The drug loaded adhesive polymer is then spread by solvent casting or in
the case of hot-melt adhesives, where, it is melted onto an impervious backing layer.
Additional layers of adhesive polymer are then applied on top of the reservoir. In the
matrix-dispersed system, the drug is dispersed homogeneously in a polymer matrix
which is either lipophilic or hydrophilic. The polymer is then placed on a backing
layer and above this matrix, an adhesive layer surrounds the matrix perimeter.

9.3.1.3 Microreservoir System

This system combines the reservoir and matrix-dispersed systems. The drug is first
suspended in aqueous solution in a water soluble polymer. This is then dispersed
homogeneously in a lipophilic polymer, which results in the formation of micro-
scopic spheres of drug reservoirs dispersed within a polymer matrix.

9.3.2 Natural Polymers in Transdermal Drug Delivery

Polymers have been used in transdermal drug delivery as far back as the 1980s.
Most transdermal patches contain a matrix of cross-linkage of linear polymer
chains from which the drug is to be absorbed into the skin (Tojo 2005). Polymers
used in transdermal drug delivery include cellulose derivatives, polyvinyl alcohol,
polyvinylparrolidone, polyacrylates, silicones and chitosan. Both natural and syn-
thetic polymers have been used either as matrices, gelling agents, emulsifiers, pen-
etration enhancers or as adhesives in transdermal delivery systems. For example
Sun (1986) reported the successful delivery of testosterone into lab rats using a
transdermal delivery system with a silicone elastomer as synthetic polymer matrix.
Another group explored the use of pectin hydrogels for the transdermal delivery
of insulin. Pectin hydrogels loaded with insulin were administered to diabetic rats
with type 2 diabetes mellitus. The results obtained showed that the transdermal
patch delivered insulin across the skin in a dose dependent manner with pharma-
cological effect (Tufts and Musabayane 2010). More recent studies explored the
use of natural polymers such as rubber latex as backing layer adhesive in nicotine
patches (Suksaeree et al. 2011). There is, therefore, scope for research into the use
of natural polymers in transdermal drug delivery.
Although synthetic polymers seem to be more commonly employed in the
development of TDD systems, natural polymers from plant and animal sources are
emerging as a preferred alternative as they pose the advantage of being biocom-
patible, biodegradable, degrading into non-toxic monomers and are more readily
available (Sharma et al. 2011; Chang et al. 2010). Synthetic polymers derived from
petroleum sources and synthetically modified polypeptides are known to have lim-
ited pharmaceutical implementations due to toxicity and slow biodegradation rates
(Shi et al. 2014; Deming 2007; Kim et al. 2014). The following section discusses
the use of natural polymers in the different parts of a transdermal patch system.
268 A. Nayak et al.

9.3.2.1 Controlled Release Systems

Natural polymers in combination with other natural and/or synthetic polymers

have been used in hydrogels for pharmaceutical application. A recent study
looked at the development of controlled release system based on thermosensitive
chitosan-gelatin–glycerol phosphate hydrogels for ocular delivery of latanoprost,
a drug used in the treatment of glaucoma (Cheng et al. 2014). The formulation
can be delivered via subconjunctival injection reducing the need for repeated dose
administration and possible side effect from conventional treatments of the condi-
tion (Gaudana et al. 2010; Cheng et al. 2014)

9.3.2.2 Matrix

Polymers are attractive for use as matrices in transdermal patches due to cer-
tain useful properties which they possess. In addition to being biodegradable
and biocompatible, they contain various functional groups that can be modi-
fied as required and combined with other materials and tailored for specific
applications.
When exposed to biological fluids, biodegradable polymers will degrade
releasing the drug that is dissolved or dispersed within them (Gilding and Reed
1979). There are on-going research studies into the application of natural poly-
mers in TDD as polymer matrices. In this area biocompatibility and biosafety
are a paramount requirement (Pietrzak et al. 1997). Release of APIs (active phar-
maceutical ingredients) from a polymer matrix occurs via various mechanisms
including polymer erosion, diffusion, swelling followed by diffusion and deg-
radation. The mechanism initiated depends on the type of system (Sharma et al.
2011).
The use of various natural polymers as matrices has been explored by differ-
ent research groups. These include natural polymers of chitosan, a polycationic
(pH 6.5 or less in solvent) natural polysaccharide which is obtained from one of
the most abundant polysaccharides in nature, chitin (Pillai et al. 2009). Chitin is a
natural polymer which forms the shells of crustaceans, some insects, fungi, yeasts
and plants. Chitosan is deacetylated chitin with a degree of deacetylation ranging
from 60 to 95 % (Zheng et al. 2001; Knaul et al. 1999).
The rate of drug delivery from a chitosan matrix can be controlled by varying
the manner in which the chains are crosslinked (Säkkinen et al. 2004). The most
common crosslinkers used for fabrication of chitosan gels are glutaraldehyde,
formaldehyde, glyoxal, dialdehyde starch, epoxy compound, diethyl squarate,
pyromellitic dianhydride, genipin, quinone and diisocyanate (Berger et al. 2004;
Mohamed and Fahmy 2012). Preparations of chitosan in the form of beads, micro-
spheres and gels have been shown to deliver drugs such as local anaesthetic drugs,
lidocaine hydrochloride and anti-inflammatory drugs, prednisolone (Sawayanagi
et al. 1982; Nishioka et al. 1990; Hou et al. 1985). Chitosan has also been used
as a matrix for transdermal delivery of large protein molecules such as insulin. It
9  Pharmaceutical Applications of Natural Polymers 269

is robustly physicochemically stable and possesses mucoadhesive property which

makes a good candidate for TDD (Dodane and Vilivalam 1998; Krauland et al.
2004; Pan et al. 2002; Ma and Lim 2003; Mao et al. 2005).
Pectin is also another natural polymer used in TDD matrices. Pectin is a water
soluble polysaccharide composed of different monomers, mainly d-galacturonic
acid, sourced from the cell walls of plants which grow on land. Pectin is commer-
cially extracted from fruits and its appearance ranges from a white to light brown
powder. Recent studies on application of pectin in TDD have looked at modifying
pectin to act as matrix for TDD (Graeme et al. 1999). In a study by Musabayane
et al. (2003), pectin was used as a matrix for delivery of chloroquine through the
skin; The results showed that pectin was effective as a matrix for TDD delivery
of chloroquine resulting in more effective and convenient treatment of malaria
(Musabayane et al. 2003). Soybean lecithin has also been used as gel matrices
to deliver scopolamine and dcoxatenol transdermally (Willimann et al. 1992).
Lecithin is a component of cells that is isolated from soya beans or eggs. It is pro-
cessed into Lecithin organogel (LO) to act as a matrix for topical delivery of many
bioactive agents into and through the skin. When purified and combined with
water it shows excellent gelating properties in non-polar solvents. LO provides a
temperature independent resistant to microbial growth as well as being a viscoe-
lastic, optically transparent and non-birefringent micellar system. LO is a dynamic
drug delivery vehicle as it dissolves both lipophilic and hydrophilic drugs. It effec-
tively partitions into the skin thereby acting as an organic medium to enhance per-
meation of otherwise poorly permeable drugs into the skin (Raut et al. 2012).
A combination of more than one polymer can also be used in a TDD matrix and
this also applies to natural polymers. For example Siddaramaiah (2009) developed
a matrix comprising of xanthan gum and sodium alginate. In vitro evaluation of
the TDD system showed good compatibility and controlled release of the model
drug Domperidone following in vitro release in a glass diffusion cell.
Other natural polymers that are being explored for use as matrices in TDD
include collagen, gelatin, agarose from seaweed, natural rubber, polyethylene
obtained from bioethanol, and polylactide (PLA), a polyester of lactic acid which
is produced from starch or cane sugar fermentation by bacteria (Sharma et al.
2011).

9.3.2.3 Rate Controlling Membrane

Rate controlling membranes are used when the TDD patch is a reservoir type
such that the rate at which the drug leaves the device is regulated by the mem-
brane which is either a porous or non-porous membrane. Various natural polymers
are being explored for use as rate controlling membranes. These polymers usually
have attributes such as good film forming properties and variable film thickness.
Mundada and Avari (2009) developed an optimised formulation of DamarBatu
(DB), a natural gum from the hardwood tree of the Shorea species such as
S. virescens Parijs, S. robusta and S. guiso. The optimised formulation was shown
270 A. Nayak et al.

to successfully deliver Eudragit RL00, the model drug. Following in vitro drug
release, skin permeation studies and other analysis concluded that Eudragit RL100
is a suitable film for TDD (Mundada and Avari 2009). In other studies DB has also
been evaluated as a rate controlling membrane for TDD of a model drug diltiazem
hydrochloride (Mundada and Avari 2009).
Gum copal, a biological polymer gum has also been tested as a film for TDD
(Mundada and Avari 2009). The effect of different plasticisers was tested on the
effectiveness of gum copal as a rate controlling membrane. The effectiveness of
the film produced was estimated from tensile strength of the film, uniformity of
the thickness, moisture absorption, water vapour transmission, elongation, fold-
ability and drug permeability. PEG400 was found to be the plasticizer which
gave the best permeability amongst those tested. However, a more sustained
delivery was achieved in vitro with a formulation containing 30 % w/w DPB
(dibutylphalate).
Another natural polymer with good film forming properties is zein. It is a pro-
tein obtained as a by-product from the processing of corn. Zein shows potential
as a low cost and effective alternative to synthetic films for TDD (Elisangela et al.
2007).

9.3.2.4 Adhesives

Adhesives are required in TDD systems to ensure the device remains in contact
with the skin. For TDD the selected adhesive must meet certain criteria such as
skin compatibility, biodegradability and good adhesion over long period due to the
long-term contact with the skin and drug formulation (Kandavilli et al. 2002).
Pressure sensitive adhesives (PSA) are materials which adhere or stick to the
surface following application of normal finger pressure and remains attached
exerting a strong holding force. When removed from the attached surfaces, PSAs
should ideally leave no residues (Pocius 1991). Adhesion refers to a liquid-like
flow which causes wetting of the skin surface as pressure is applied with the adhe-
sive remaining in place after the removal of the applied pressure. The adhesion is
achieved as a result of the elastic energy that has been stored during the breaking
of bonds caused by applied pressure. The effectiveness of the PSA is, therefore,an
attributable to the relation between viscous flow and stored elastic energy (Franz
et al. 1991). Synthetic polymers seem to have dominated the adhesives used in
TDD. Commonly, used ones include acrylic, polyisobutylene and silicones (Dimas
et al. 2000; Barnhart and Carrig 1998; Tan and Pfister 1999).
Use of adhesives on skin is an idea that has been around for many decades, one
of the earliest applications being in bandages for wound healing by Johnson and
Johnson company in 1899 (Subbu and Robert 1998). When deciding on what kind
of polymer to incorporate as an adhesive, an understanding of the properties of the
skin is essential. The surface energy of the skin, which acts as the adherent in the
case of TDD, must be greater than or equal to the surface energy of the adhesive
(Subbu and Robert 1998). Furthermore the skin properties vary with the factors
9  Pharmaceutical Applications of Natural Polymers 271

such as age, gender, race and environmental conditions. Therefore, the effect of
properties such as moisture content of skin and the viscometric property of the
adhesive should be established (Subbu and Robert 1998).
Adhesives in transdermal patches may exist as a single adhesive layer or a drug
in adhesive type, the latter is preferred as the simplest to apply however, it is rather
complicated to produce. For drug-in-adhesive type patches, issues which must
be addressed include the tendency of the drug or adhesive to crystalize. This will
have an effect on the drug delivery rate as it permeates through the adhesive layer
(Variankaval et al. 1999).
Pressure sensitive adhesives generally comprise an elastomeric polymer, a resin
for tack, a filler, antioxidants, stabilisers and crosslinking agents. Although syn-
thetic polymers seem to be more commonly used as adhesive in TDD systems, the
development of adhesives from natural polymers is becoming a rather attractive
area of interest (Doherty et al. 2011). Various sources in nature have been explored
for obtain adhesives.
Carbohydrates are readily available polymers of plants. Cellulose, starch
and gums are the most common forms that are used in production of adhesives
(Baumann and Conner 1994). There are studies which have been focused on
the production of adhesives obtained from cellulose recovered from domes-
tic and agricultural waste. These include soy protein, raft lignin and coffee bean
shells (Weimer et al. 2003; Chung and Washburn 2012; Khan and Ashraf 2005).
Adhesives formed from carbohydrates include carboxymethyl cellulose (CMC),
hydroxyethyl cellulose, ethyl cellulose, methyl cellulose, cellulose acetate and
cellulose nitrate. Those formed from starch such as tapioca, sago and potatoes
can be more readily converted to adhesives following modification through heat-
ing, alkali, acidic or oxidative treatment (Baumann and Conner 1994). The adhe-
sives often require further additives during processing. Recent studies focused on
extracting natural polymeric adhesives include that by Hoong et al. (2011) which
studies acacia mangium bark extracts as a source of natural polymer adhesives.
The dicotyledonous tree bark which is commonly grown in Malaysia as a source
of raw material for veneer, pulp and paper showed a promising prospect as an
alternative to adhesives produced from petrochemicals.
In other works adhesive production from waste materials such as de-inked
waste paper has been studied (Mishra and Sinha 2010). In a particular study de-
inked waste paper from magazines were washed using detergent under stirring.
This was then followed by further processing under heat at 150 °C and treatment
with acid and ethylene glycol. The glycosides which resulted from the breaking
down of the cellulose were then transesterified using rice-bran castor and soy oils
to convert it to polyols. Polyurethenes are then produced from the polyols. The
adhesives produced using the methods described when tested showed strong adhe-
sive properties than the commercial adhesives and also showed significant water
resistance. Marine organisms (Waite 1990) and bacteria have also been shown to
be the sources of natural adhesives. The main limitation with these sources is the
expensive production process.
272 A. Nayak et al.

9.3.2.5 Penetration Enhancers

Polymers are also used as penetration enhancers to aid the permeation of drugs
across skin. Polyethylene glycol solution is an example of such penetration
enhancers of prodrugs across skin models (Hikima and Tojo 1993). However use
of polymers as additives in formulations also carries some limitations such as
inhibiting the bioconversion of the drug (Tojo 2005). Transdermal films incorpo-
rating 0.5 % tenoxicam have been developed from varying ratios of glycerol, PEG
200 and PEG 400. Using Fourier transform infrared spectroscopy, it was found
that increasing the concentration of PEG enhanced the penetration of tenoxicam
into the skin (Nesseem et al. 2011). Polymers are also employed as other formula-
tion additives in the form of viscosity enhancers and as emulsifiers. Chitosan, a
natural polymer has been used as a penetration enhancer, which acts by opening
up the tight junctions which exists between epithelial cells (Cano-Cebrián et al.
2005; Mao et al. 2005; Gao et al. 2008; Avadi et al. 2005; Kotzé et al. 1997).
Recently, research studies aimed at fabricating micron-sized penetration
enhancers which partially disrupt the stratum corneum layer creating a more per-
meable pathway for drugs to enter into the skin via natural polymers is emerging.
For example a study by You et al. (2011) where dissolving polymer microneedles
were fabricated from silk Fibroins obtained from bombyx mori silk worm. The
resulting structures were rapidly dissolving microneedles with adjustable mechani-
cal parameters and were biocompatible with skin. Maltose has also been used to
fabricate dissolving polymer microneedle using traditional casting methods as
well as using the extrusion drawing method (Lee et al. 2011). More recent studies
have looked at the application of hydrolyzed collagen extracted from fish scales
for production of microneedles as mechanical penetration enhancers (Olatunji
et al. 2014).

9.3.2.6 Backing Layer

The backing layer comes in contact with the drug matrix or reservoir therefore the
chemical inertness of the material used for the backing layer is required. The back-
ing layer must also be compatible with the excipient formulation. Back-diffusion
of the drugs, penetration enhancer or excipient must not occur even over a long
period of contact. While maintaining chemical inertness it must also be ensured
that the backing layer is flexible enough to allow movement, transmission of mois-
ture vapour and air in order to prevent skin irritation during long-term contact with
skin. Adequate transmission of moisture vapour and air also prevents the weak-
ening of the adhesive hold on the skin surfaces (Kandavilli et al. 2002; Rolf and
Urmann 2000a). In more modern designs of TDD patches, the backing layer could
be solidified with the reservoir to form a single structure such that it serves as a
storage space for the reservoir (Rolf and Urmann 2000b; Kandavilli et al. 2011).
More recent studies have explored the use of natural polymers as backing layer of
nicotine transdermal patches from natural rubber latex (Suksaeree et al. 2011).
9  Pharmaceutical Applications of Natural Polymers 273

9.3.2.7 Release Liner

The adhesive side of the transdermal patch is usually covered with a liner which
protects the adhesive and the rest of the patch during storage. Although mostly for
packaging purpose, the liner is in direct contact with the adhesive layer throughout
the storage period. The material used as a release liner should be chemically inert
(Wokovich et al. 2006) and resistant to the permeation of the drug, penetration
enhancer and moisture. The liner should also not cross link with the adhesive such
that it becomes difficult to remove (Pfister and Hsieh 1990). Example of a release
liner used in commercial TDD is the ScotchPakTM 1022 and ScotchpakTM 9742
liner which are produced from fluoropolymers by 3M Drug Delivery Systems
(available in 3M product catalogue Product ID 70000065659).
Although currently the use of synthetic polymers seem to dominate that of
natural polymers in TDD, there is increasing research interest in incorporating
natural polymers in new ways in TDD systems (Valenta and Auner 2004). This
is attributable to the desire to produce pharmaceutical products with more desir-
able environmental impacts, reduce dependency on fast diminishing petrochemical
resources and developing more sophisticated TDD systems with better effective-
ness and biosafety (Klingenberg 2013). However, there is yet to be a transder-
mal drug delivery system which is developed fully from natural polymers. The
dependency on synthetic polymers therefore still persists. Future research efforts
directed towards developing novel natural polymers from new biological sources.
Consequently as new polymers emerge, extensive studies will be required to iden-
tify the physical and chemical properties of the new biomaterials. Furthermore
developing newer processing methods and new combinations of polymers could
be optimised leading to improved effectiveness in transdermal drug delivery.
Natural polymers have proven valuable in transdermal drug delivery systems.
They have a wide range of applicability and pose several advantages over syn-
thetic polymers in this application. Nature offers an abundant supply of polymers
with numerous properties. Understanding these sources and properties allow us to
further modify these polymers to suit specific requirements. The area of transder-
mal drug delivery still faces certain limitations such as skin irritation and limited
range of drugs which can be delivered through this means. Exploring new poly-
mers from natural sources could provide new solutions and offer clinical and com-
mercial development in the area of transdermal drug delivery.

9.4 Topical Drug Delivery

Delivery of drugs into the body topically can be employed to treat conditions
which exist on or close to the surface of the skin. This could vary from aches and
bruises to severe burns and mild and chronic conditions such as eczema and psori-
asis. This form of delivery refers to when a drug formulation is applied directly to
the external skin surface or surface of the mucous membrane of the vaginal, anal,
274 A. Nayak et al.

oral, ocular or nasal area for local activity (Joraholmen et al. 2014; Mekkawy et al.
2013; Gratieri et al. 2011; Singla et al. 2012). Topical delivery through the other
entry routes (i.e. oral, vaginal, ocular, etc.) is not to be confused with the other
forms of delivery which are discussed in other sections of this chapter.

9.4.1 Advantages and Disadvantages

Topical delivery is relatively convenient and has relatively better patience compli-
ance than, e.g. oral or intravenous injection which could impose adverse impacts
such as nausea, low bioavailability due to metabolism of drug in the gastrointesti-
nal tract, needle phobia and general preferences. The specificity of topical delivery
is also advantageous as it can be directly applied to the affected area to act locally,
similarly the medication can be easily terminated by simply cleaning off the medi-
cation. Topical delivery particularly becomes a favourable option where other
routes of entry into the body are deemed unnecessary or unsuitable depending on
the individual or nature of drug. In cases where for instance oral delivery of the
drug could induce adverse effect which could even is more severe than the actual
condition being treated. For instance many of the adverse effect associated with
antifungal drug fluconazole are gastrointestinal related and could be avoided by
applying a topical formulation for effective delivery of the drug (Mekkawy et al.
2013).
Main challenges in the area of topical drug delivery alongside skin irritation
and allergic reaction include skin penetration into target region especially for
drugs with large particle size. In particular, situations such as in fungal infection
where the penetration into the stratum corneum is further inhibited as an attack
mechanism of the pathogen to prevent shedding of the stratum corneum, penetra-
tion enhancement of the topical agent becomes of relative importance in the effec-
tiveness of the drug formulation (Del Palacio et al. 2000; Mekkawy et al. 2013).

9.4.2 Composition of a Topical Formulation

The main components of a topical formulation includes a vehicle which could be

in the aqueous form, mainly water or alcohol, or it could be an oil such as min-
eral oils, paraffin, castor oil, fish liver oils, cotton seed oil, etc. A vehicle should
maintain effective deposition and even distribution of the drug on the skin; it
should allow delivery and release to the target site and maintain a pharmacologi-
cally effective therapeutic concentration of the drug in the target site. In addition
to these properties a suitable vehicle should be well formulated to meet patient’s
cosmetic acceptability and be well suited for the anatomic site.
Emulsifiers are important to maintain stability and the distribution of the water
and oil emulsion throughout the shelf and usage lifespan of the formulation.
9  Pharmaceutical Applications of Natural Polymers 275

Typical synthetic emulsifiers include polyethylene glycol 40 stearate, sorbitan

monooleate (commercial name: Span 80), polyoxyethylene sorbitan monooleate
(commercial name Tween 80), stearic acid and sodium stearate. Natural poly-
mers used as emulsifiers include starch, gum acacia, alginates, xanthan gum,
irvingia gabonensis mucilage, and tragacanth gum (Ogaji et al. 2011). Gelling
agents are also important in increasing the bulk of the drug and thicken the topi-
cal formulation according to stable viscoelasticity. Examples include sodium algi-
nate, cellulose in modified forms as sodium carboxymethyl cellulose (NaCMC),
hydroxypropylmethyl cellulose (HPMC) and hydroxypropyl cellulose (HPC)
(Mekkawy et al. 2013).

9.4.3 Types of Topical Formulations

Topical drug delivery systems could be in the form of gels, emulgels, emulsions,
liposomes, liquids, powders and aerosols. Gels and emulgels are relatively new
forms of topical delivery formulations. Gels are formed when a large amount of
aqueous or hydro-alcoholic solutions are entrapped within a network of colloidal
solid particles or macromolecules, while emulgels are a combination of a gel and
emulsion. Emulgels are targeted at addressing the limitation of gels to delivery of
hydrophilic compounds by enabling the delivery of hydrophobic compounds better
than using gels or emulsions. To create emulgels for hydrophobic drugs, oil-in-
water (o/w) emulsions are needed to entrap the hydrophobic drugs followed by
addition of a gelling agent to the emulsions, while for hydrophilic drugs; a water-
in-oil (w/o) emulsion is used. The desirable features of an emulgel include more
effective cutaneous penetration, greaseless, spreadability, extended shelf life com-
pared to gels or emulsions, biofriendly, non-staining, water soluble, moisturising
and a generally transparent and pleasing appearance.

9.4.4 Natural Polymers in Topical Delivery Systems

Natural polymers are used in topical drug delivery as gelling agents, emulsifi-
ers, stabilizers, thickeners, etc. Cellulose, alginates, chitosan, albumin, starches
and xanthan gum are examples of natural polymers which have been applied in
the production of topical formulations (Timgren et al. 2013; Gratieri et al. 2011;
Laxmi et al. 2013). The derivatives of cellulose such as HPMC or CMC are par-
ticularly common candidates in topical formulations and they pose a good alterna-
tive to the commonly used carbopol, a synthetic polymer (Singla et al. 2012).
Gels are of interest for topical delivery of pharmaceutical agents as they are easy
to apply, spread and remove, thus encouraging patience compliance. Excipients
used in topical delivery of psoralen using natural polymers; pectin, xanthan gum,
egg albumin, bovine albumin, sodium alginate and guar gum are compared in
276 A. Nayak et al.

Fig. 9.2  Comparing diffusion profiles of topical drug, psoralen using various natural polymer-
based excipients (a) and (b). Sourced from Laxmi et al. (2013) under creative commons attrib-
uted licence

Fig.  9.2. Table 9.1 shows the reagent component concentrations of the respective
polymer, humectant, drug, solvent, antioxidant and preservatives in a developmen-
tal formulation of Psoralen, labelled F1–F8 (Laxmi et al. 2013). Psoralen is a drug
used in the treatment of skin conditions such as psoriasis, vitiligo, mycosis fun-
goides and eczema, but also possesses antitumor, antibacterial and antifungal prop-
erties. It belongs to a class of furanocoumarins compounds found in the psoralea
corylifolia L. plant (Ahmed and Baig 2014).
The psoralen gel formulations were prepared by first mixing the polymer in
water and stirring continuously at 37 °C. This was followed by addition of gel-
ling agent and continued mixing until a homogenous dispersion was attained.
The required drug dissolved in methanol was then added followed by addition of
antioxidant, preservatives and humectants. The mixture was then stirred until a
homogenous mixture was obtained.
All polymers used showed good compatibility with the drug. This is important
as an interaction between the excipient and the drug formulation will likely affect
the drug activity and could also pose some adverse health effects. This is not to
say that all natural polymer excipient do not interact with the drug compound or
9  Pharmaceutical Applications of Natural Polymers 277

Table 9.1  Various formulations of Psoralen using natural polymer excipients adopted from

Laxmi et al. (2013) under creative commons Licence
Materials Formulation code
F1 F2 F3 F4 F5 F6 F7 F8
Psolaren (g) 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
Sodium alginate (g) 0.75 0.75 – – – – – –
Egg albumin (g) – – 0.75 0.75 – – – –
Bovine albumin (g) – – – – 0.75 0.75 – –
Pectin (g) – – – – – – 4 5
Xanthan gum (g) 0.50 – 0.75 – 0.75 – – –
Guar gum (g) – 0.50 – 0.75 – 1.75 – –
Menthol (g) 0.25 0.25 0.25 0.25 0.25 0.25 0.25 0.25
σ-Tocopherol (g) 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50
Barbaloin (g) 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005
Glycerin (mL) – – – – – – 5 –
Eugenol (mL) 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01
Methanol (mL) 10 10 10 10 10 10 10 10
Distilled water to make (mL) 50 50 50 50 50 50 50 50

psoralen in particular. The tendency of interaction between excipient and drug

compound depends in the specific drug and specific polymer. While a polymer
might show the desired biomechanical properties, release kinetics, bioactivity, etc.
the applicability may be limited if there is interaction between the polymer being
used as excipient and the active drug compound. For instance, nanofibrillar cel-
lulose gels show good potential for drug delivery (Laurén et al. 2014); however,
nanofibrillar cellulose possesses various carboxyl and hydroxyl groups which may
interact with drug compounds in different ways. This, therefore, must be investi-
gated for every new formulation.
Interaction between excipient and drug compound is commonly evaluated using
FTIR. Compatibility is indicated when the characteristic peaks of the pure drug
are retained in the FTIR spectra of the drug formulation with the excipients pre-
sent. Figure 9.3 shows the FTIR spectra of pure psoralen next to that of formula-
tion of psoralen in albumin and xanthan gum as polymer excipients.
Of the polymers investigated, the formulation containing xanthan gum and egg
albumin showed the best drug incorporation, release kinetics and in vitro antipso-
riatic activity (Laxmi et al. 2013).
Topical delivery system should possess sufficient pseudoplasticity and con-
trollable release kinetics. Sodium alginate and derivatives of cellulose, sodium
carboxymethyl cellulose, hydroxypropylmethyl cellulose and hydroxypropyl cel-
lulose when applied as excipients for topical delivery of fluconazole showed desir-
able pseudoplastic behaviour. This pseudoplastic behaviour is a shear thinning
property that allows the topical formulation to be effectively spread with ease on
the affected area while remaining in the required region for localised and sustained
278 A. Nayak et al.

Fig. 9.3  FTIR spectra of psolaren (a) and psolaren in a formulation of egg albumin and Xanthan
gum (b). Sourced from Laxmi et al. (2013) under creative commons attributed licence

delivery. The release kinetics and viscosity also vary with the concentration of
the polymer such that the release rate and viscosity can be varied as required by
varying the concentration of the polymer as desired. Although a synthetic gel-
ling agent, carbopol showed the best drug release profile and anti-fungi activity;
the other polymers also had sufficient antifungal activity and drug release rate
(Fig. 9.4).
Over the 3 h observed, the release rate of the fluconazole increased as the con-
centration of the polymer id reduced (Mekkawy et al. 2013). This can be attributed
to increased porosity as polymer concentration reduces, allowing easier permea-
tion of the drug compound through the polymer matrix of the gel.
9  Pharmaceutical Applications of Natural Polymers 279

Fig. 9.4  Effect of various polymer excipients on the release profile of fluconazole from prepared gel

The ability to control and predict release kinetics of drug formulation is impor-
tant in the effective drug delivery. Here, we see gels from natural polymers show-
ing controllable parameters comparable to that of synthetic polymers.
In the treatment of fungal keratitis, delivery and bioavailability of the antifungal
agent can be enhanced by using chitosan-based formulations either in gel or solu-
tion. Topical formulations of fluconazole using chitosan solution and a gel sys-
tem of chitosan with a thermoresponsive polymer poloxamer as vehicles showed
improved bioavailability of fluconazole in the eye compared to aqueous solu-
tions. The aqueous solutions used as eye drops have limited effectiveness due to
the eye’s inherent defence mechanism which prevents penetration of foreign sub-
stances (Fig. 9.5). The chitosan-based formulation in solution and gel when tested
on rabbit models in vivo and across porcine cornea ex vivo at a time of nearly 2 h
retained the drug in the desired area allowing more of the drug to penetrate leading
to increased bioavailability (Fig. 9.5) (Gratieri et al. 2011).
The mucoadhesive property of chitosan also makes it applicable for applica-
tion in topical gels for localised and effective delivery topically. In the case of
pregnant women where care must be taken to avoid systemic absorption of certain
drugs such that the drug being administered to treat the mother does not get to
the child as the drug, although beneficial to the mother might pose harm to the
child. It is therefore desired that the drug be localised to the affected tissue as
280 A. Nayak et al.

Fig.  9.5  Enhanced topical ocular delivery of fluconazole using chitosan-based solution

and gel (Gratieri et al. 2011). Reproduced with permission from Elselvier (Licence number
3631870446393)

best as possible. An example is the delivery of clotrimazole using chitosan-coated

liposomes for the treatment of vaginal infection which occurs during pregnancy
(Joraholmen et al. 2014). Vaginal infection although might heal without treat-
ment in non-pregnant women, in pregnancy must be treated to prevent complica-
tions at child birth or affect development of the child. Drug treatment provides
adverse effects involving current drug regimens because of very high therapeutic
levels in the bloodstream despite favourable long durations of action. For exam-
ple, trichomoniasis is a vaginal infection when treated with metronidazole before
37 weeks pregnancy substantially increases the adverse effects of preterm labour
and low birth rate babies (Hainer and Gibson 2011). The drug metronidazole is
commonly prescribed to pregnant women in oral dosage form (500 mg or 250 mg)
(Hainer and Gibson 2011). Further research in decreasing the adverse effects,
maintaining an ideal therapeutic level and long sustainable duration of action for
metronidazole is much sought after. Chitosan-coated liposomes containing 0.1,
0.3 and 0.6 % w/v concentration of chitosan and a drug concentration of 22 g/
mg lipid of Clotrimazole, show good localised delivery of the drug (Joraholmen
et al. 2014). The retention of the drug in the vaginal tissue was also significantly
increased by use of chitosan, (Fig. 9.6). Interestingly, it was also shown that the

Fig. 9.6  Comparing retention of the drug clomirazole at vaginal site using varying concentration
of chitosan. Reproduced with permission from Elselvier Licence number 3631861429984
9  Pharmaceutical Applications of Natural Polymers 281

clotrimazole-containing liposome system with lower concentration of chitosan

showed better mucoadhesive property than the higher concentration of chitosan.
The topical formulation effectively adheres to the tissue preventing penetration
into the systemic flow such that the drug does not cross the placenta to the child
but remains in the tissue where it is needed to act.

9.5 Oral Drug Delivery Systems

Drug delivery through the oral route is one of the most common forms of drug
delivery into the body (Elsayed et al. 2009; Muheem et al. 2014). Oral drug deliv-
ery refers to the intake of medicaments into the body through the mouth by swal-
lowing, chewing or drinking. These 87 dosage forms could be in form of solid or
liquids as tablets, capsules, powders, liquids. Oral dosage forms could be targeted
at any tissue in the body and for a variety of purposes from general pain relief to
regulation of insulin in diabetes patients.

9.5.1 Advantages and Disadvantages of the Oral Route

In certain cases, the oral route becomes more than just an alternative to other
routes of drug delivery. For example, insulin delivery, where oral route provides
an administration which is closer to the natural physiology of the body by deliver-
ing the drug into the liver which is the target tissue. The drug passes into the liver
via the pancreatic β cells through the hepatic portal vein. This is unlike in the case
of other delivery routes such as parenteral or nasal which aim to deliver the drug
directly into the systemic circulation. While this route is favourable in avoiding the
first pass metabolism, it is not in line with insulin’s natural physiological pathway
(Rekha and Sharma 2013; Muheem et al. 2014).
Protein drugs such as insulin pose a particular challenge in oral delivery as they
are more likely to follow the paracellular route rather than the lipophilic mem-
brane route which most other drugs follow. This makes them more susceptible to
enzymatic degradation.
The main limitations in oral delivery route are the first pass metabolism and
biodegradation in the gastrointestinal tract which adversely impacts on the bio-
availability of the drug in vivo. Scientific focus in the area of oral drug delivery
looks at developing oral formulations which can successfully pass through the
gastrointestinal tract while still remaining potent, resist enzymatic degradation at
the mucous membrane, can be effectively transported through the complex struc-
ture of the mucous membrane, get absorbed into the targeted tissue and have the
desired pharmacological activity after passing through the mucous layer (Muheem
et al. 2014).
282 A. Nayak et al.

9.5.2 Current Challenges and Natural Polymer-Based

Innovations in Oral Drug Delivery

Mucoadhesive polymers are applied with the aim of developing a delivery sys-
tem which enables the drug to attach to the mucous membrane for enhanced per-
meation and sustained delivery. However, limitation of this procedure lies in the
constant renewal of the mucous layer which inhibits mucoadhesive drug delivery
systems (Muheem et al. 2014; Ponchel and Irache 1998).
Although rate of drug absorption using any kind of route (e.g. oral, nasal,
topical) depends on factors such as age, diet and state of health of the patient
(Morishita and Peppas 2006), the drug properties also has a significant effect on
the rate of absorption and effectiveness. The drug properties which affect oral
delivery include molecular weight, particularly drugs with molecular mass greater
than 500–700 Da like protein drugs such as insulin. Lower molecular weight drugs
are generally easier to absorb.
While their oral delivery would be of much significance pharmaceutically,
delivery of proteins and peptides-based drugs orally have particularly proven chal-
lenging. This is mainly due to their generally large molecular weight and the ten-
dency to be digested in the body without serving their purpose. There are about
two known oral protein and peptide drugs in clinical development and these are
Interferon-alpha and human growth hormone (HGH) while more are being studied
for potential pharmaceutical application. Of much interest is the oral delivery of
insulin.
Research approaches in enhancing the oral delivery of proteins include reduc-
ing the particle size and using biodegradable nanoparticles (Bakhru et al. 2013).

9.6 Parenteral Drug Delivery Systems

Parenteral delivery concerns the delivery of drugs invasively through the skin, eye,
vein, artery and spinal cavity. Substantial efforts in formulating a documented plan
in the development of hypodermic needles was first initiated by Lafargue in 1836
(Howard-Jones 1947). Lafargue immersed the lancet in morphine and diluted the
morphine by a once repeated immersion into water before self-injection (Howard-
Jones 1947). The hypodermic needle is a cylindrical tube with an elliptical shaped
bevel end forming a sharp tip for the purpose of cutting into skin (Hamilton 1961).
Hypodermic needles are conventionally fabricated from medical grade stainless
steel. The luer lock is the plastic connector between the hypodermic needle and
syringe body. Polyethylene and polypropylene are medical grade thermoplastics
moulded into the luer lock (Gilson and Windischman 1983). The syringe body is
composed of medical grade plastic. Medical grade thermoplastics can be moulded
into complex geometries in a process known as injection moulding. Medical grade
plastics are regulated by USP with the aim of analysing if a grade of plastic reacts
9  Pharmaceutical Applications of Natural Polymers 283

with mammalian cells cultures. There is no published material about syringes

constructed from natural polymer materials. This is because most natural poly-
mers may not be easily mouldable by injection moulding and end product assur-
ance towards medical grade is less likely due to the risk of by-product toxicity
if a reagent in a natural polymer blend is unstable despite high desirable yields.
Hypodermic needles and syringes are usually disposable and single use only.
Complex blended natural polymers such as sorn starch blended with clay, mineral
montmorillonite and modified natural rubber latex were injection moulded thus
resulting in good tensile strength and elastic modulus properties (Mondragón et al.
2009). The constraints for complex blended polymers are greater costs than con-
ventional process, longer duration in process manufacturing and end product can
be unaesthetically pleasing. In the past, syringes were constructed from borosili-
cate glass and autoclavable for reuse thus producing less of an ecological impact.

9.6.1 Advantages and Disadvantages of Parenteral

Drug Delivery

Parenteral drug delivery is still a common and widely accepted route to drug
administration. The main advantages are bypassing gastrointestinal tract metabo-
lism, rapid drug delivery with target-based response and is an alternative route
for patients with difficulty ingesting their medication or are completely sedated
(Breymann et al. 2010; Jain 2008). The disadvantages are depth-related localised
pain, likelihood of peripheral nerve injury and accidental piercing of a blood ves-
sel at hypodermis level (Jain 2008).

9.6.2 Properties of Parenteral Drug Molecules

Injection-based parenteral drug molecules are usually high molecular weight,

more ring-based structural configuration, high counts for proton acceptors and
lowest Log10 o/w (Vieth et al. 2004). Fluid-based drug formulations are ideal for
flow-based transfer along hollow hypodermic needles. Surface tension forces are
the usual forces that allow fluid to travel along capillary tube. The volumetric flow
rate of a fluid inside a microcapillary is defined by the Hagen–Poiseuille (Eq. 9.1)
(Holzman 1998; Allahham et al. 2004).

πr 4
 
Q = �P (9.1)
8 µL

where Q is the volumetric flow rate inside the hypodermic needle, ΔP is the
pressure difference from Eq. 9.2, F is the injection force, f is the frictional force
from the tube and syringe walls, A is the interior cross-sectional area of the tube
284 A. Nayak et al.

and r is the internal tube radius, µ is the fluid viscosity and L is the hypodermic
needle length.

πr 4
 
Q = �P (9.2)
8 µL

The characteristic of fluid flow is expressed by the Reynolds number, Re (Eq. 9.3)

(Ashraf et al. 2010)
ρdV
Re = (9.3)
µ
where ρ is fluid density, d is the internal tube diameter, V is the fluid volume. A
Reynolds number of 2100 or less indicates laminar flow and turbulent flow is
above this value (Ashraf et al. 2010).

9.6.3 Current Proprietary Parenteral Devices

Parenteral devices are commonly injectables and examples of current devices

available on the market are mentioned. Injectable devices for the delivery of soft
implants subcutaneously are patented and commercially available from Rexam
(www.rexam.com). Also pre-filled drug syringes is registered Safe ‘n’ Sound, pat-
ented and commercially available from Rexam (www.rexam.com). A self-injector
trademarked SelfDose for the safe delivery of drugs is in the format of an adap-
tor for fitting syringe formats is commercially available from West Pharma (www
.westpharma.com). Another self-injector device has a window indicator regarding
usage and is trademarked Project, patented and commercially available from Aptar
(www.aptar.com).

9.6.4 Future Challenges of Parenteral Devices

In this chapter, we have discussed microneedles as minimal invasive parenteral

devices because the needles are fabricated to penetrate a known depth in skin lay-
ers than a hypodermic needle. Natural polymers have the potential to support the
sustained release of drugs in the skin and can prove advantageous for the biode-
gradable class of microneedles. However, the challenge arises to strengthen the
microneedles with the result of all microneedles piercing the skin at a reproducible
depth. Synthetic biodegradable polymer such as poly(dl-lactic-co-glycolic acid)
PLGA and poly(l-lactic acid) (PLLA) possess high mechanical strength (Ishaug
et al. 1994; Leung et al. 2008). The possibility of enhancing the natural poly-
meric formulation with blended synthetic, polymeric fibres in providing improved
mechanical strength properties is one direct solution.
9  Pharmaceutical Applications of Natural Polymers 285

9.7 Nasal Drug Delivery Systems

Nasal delivery is one of the oldest drug delivery systems originating from Ancient
Indian Ayurveda called Nasya Karma. The mucosal epithelium inside the nasal
cavity is an area for non-invasive drug delivery. This epithelial layer located
in the inferior turbinate of the nasal cavity is highly vascularised with a signifi-
cant absorption area (150 cm2) and projections of microvilli in epithelial cells
(Grassin-Delyle et al. 2012; Lan Kang et al. 2009). The nasal cavity is covered
with mucous membrane comprising of goblet cells, columnar cells and basal cells
(Fig.  9.7). Most cells of the nasal cavity have cilia apart from columnar cells in
the anterior cavity (Fig. 9.7). A collective group of microvilli are known as cilia.
Cilia move rhythmically in waves with a function to clear mucus from the nasal
cavity into the nasopharynx followed by the oesophagus before finally moving
towards the gastrointestinal tract. The microvilli contribute to the large surface
area thus highly desirable for effective drug absorption into the nasal mucosa. The
nasal mucosa is neutral pH and permeable to numerous drug molecules. Mucosa
is usually comprised of lipids, inorganic salts, mucin glycoproteins and water. The
main functions of mucus are lubrication of surfaces and protection. The function
of protection are goblet cells and mucus glands of nasal epithelium that prevent
the absorption of foreign chemicals and decrease residence time for any applied
drugs that are in surface contact with the epithelial lining. The purpose for nasal
drug delivery is to target the drug systemically such as peptides or proteins in the
bloodstream locally (Illum 2012) such as a nasal allergy, nasal congestion, sinus,
and to target the central nervous system (CNS) such as bypassing the blood-brain

Fig. 9.7  Histology of the nasal cavity morphology (Uraih and Maronpot 1990)

286 A. Nayak et al.

barrier (Illum 2012). The purpose of targeting the CNS is to develop drugs for
rapid treatment of migraine, headaches, advanced neurodegenerative illnesses such
as Alzheimer’s and Parkinson’s disease.

9.7.1 Advantages and Disadvantages of Nasal Drug Delivery

The advantages of nasal drug delivery are avoidance of potential gastrointestinal

and hepatic first pass metabolism (Grinberg and Gedanken 2010; Lan Kang et al.
2009), low molecular weight drugs have a good bioavailability via the nasal route,
straight forward self-administration and protein-based drugs are able to absorb
through the nasal mucosa as an alternative to parenteral drug delivery (Grassin-
Delyle et al. 2012). The disadvantages of nasal drug delivery are possibility of
irreversible cilia damage on the nasal mucosa caused by the drug formulation
(Grassin-Delyle et al. 2012), high molecular weight molecules and polar mol-
ecules may not permeate or result in low permeation thorough nasal membranes
(molecular weight threshold: 1 kDa) (Illum 2012; Grassin-Delyle et al. 2012),
clearance of mucosa frequently by cilia has the potential to decrease or prevent
full drug absorption (Patil and Sawant 2009), nasal mucosa could denature and
change the structure of some drugs through enzymes and possible incompatibility
observed between drug and nasal mucosa interaction (Grassin-Delyle et al. 2012).

9.7.2 Natural Polymers in Nasal Drug Delivery

Mucoadhesive microspheres, liposomes, solutions, gels and Mucoadhesive

hydrogels are vehicles commonly adopted in the nasal delivery of drugs. Starch,
Chitosan, alginate, dextran, hyaluronic acid and gelatin are natural polymers
adopted for nasal drug delivery. Mucoadhesion is defined as the contact between
the drug formulation and the mucin surface. The concept of mucoadhesion is to
allow sustained drug delivery in nasal membranes by prolonging the contact time
between the drug formulation and nasal mucosa layers in the cavity (Duan and
Mao 2010). Mucoadhesion promotes drug absorption and lowers the chances of
complete mucociliary clearance (Patil and Sawant 2009).
Starch is a biodegradable polysaccharide which can be readily processed into
microspheres (Grinberg and Gedanken 2010). Starch microspheres commercially
available under the name Spherex are used in nasal drug delivery (Pereswetoff-
Morath 1998; Grinberg and Gedanken 2010). Drugs such as Insulin (Duan and
Mao 2010), morphine (Illum et al. 2002), inactivated influenza (Coucke et al.
2009) and Salbutamol (Xu et al. 2014) are examples of starch loaded intranasal
drugs at developmental stage.
Chitosan is a natural polysaccharide with mucoadhesive properties thus it has
very good binding properties to nasal epithelial cells and the covering mucus layer
9  Pharmaceutical Applications of Natural Polymers 287

(Illum 2003). The cationic nature of chitosan readily permits the electrostatic
attraction with the negatively charged mucosal surface (Martinac et al. 2005).
There has been a wealth of research published on chitosan for intranasal deliv-
ery according to variable salt forms, degrees of acetylation, variation in deriva-
tives, variation in molecular weights and variation in physical form such as gel,
microspheres (Casettari and Illum 2014). Drugs such as Loratadine (Martinac
et al. 2005), Zolmitriptan (Alhalaweh et al. 2009) and Insulin (Chung et al. 2010)
are examples of loaded chitosan-based intranasal drugs at developmental stage.
However, there is yet to be a marketed nasal drug product containing chitosan as
the drug absorption enhancer. A morphine intranasal formulation containing chi-
tosan (Rylomine) has already published phase 2 clinical trials and has already pur-
sued phase 3 clinical trails (Javelin Pharmaceuticals; Casettari and Illum 2014; the
Pharma Letter).
Alginate is a divalent cation-induced rapid gelation, natural polysaccharide
with greater mucoadhesion strength as compared with chitosan, PLA and carboxy-
methyl cellulose (Patil and Sawant 2009). Usually alginate gel is blended with one
or more mucoadhesive polymers in order to improve the strength and drug loading
efficiency of the vehicle (Pal and Nayak 2012). Drugs and macromolecules such
as bovine serum albumin in representing a water soluble antigen (Lemoine et al.
1998) Carvedilol (Patil and Sawant 2009) and Terbutaline Sulphate (Moebus et al.
2009) are examples of alginate loaded intranasal drugs at developmental stage.
There appears to be no significant proprietary drugs containing alginate as the
vehicle for intranasal drug delivery.

9.8 Hydrogel-Based Drug Delivery Systems

The need in optimised semi-solid, biocompatible, polymeric formulations in

drug loading and routes of entry in the human body is still a growing area in
pharmaceutics. Gel-and ointment-based drug formulations are normally oily
and thick in appearance (Mueller et al. 2012). A common purpose of such semi-
solid, polymeric gel/ointment formulations are to enhance the viscoelasticity
(Teeranachaideekul et al. 2008; Silva et al. 2007) and improve target-based phar-
macokinetics such as enhanced permeability of luteinizing-hormone, releasing
hormone (LH–RH) from polycarbophil hydrogels inside the vagina compared
with solution (Valenta 2005). In terms of viscoelasticity, an example in enhanc-
ing pseudoplastic properties for oral Ibuprofen is Carbopol-based hydrogels (Silva
et al. 2007). Limitations for semi-solid formulations such as topical applications
concerning transdermal drug routes of delivery are one common area (Dubey et al.
2007). Hydrogels can be considered as a semi-solid matrix for the purpose of con-
trolled drug release (Jacobs 2014; York 1996). Hydrogels can change structural
configuration during certain temperature or pH-induced environments in bodily
systems (Cai et al. 2013; Nguyen and Lee 2010). Usually, hydrogels are known
to release trapped drug molecules by swelling in watery plasma solvent (Li et al.
288 A. Nayak et al.

2014b). Distinct variability from conventional swelling mechanism of active mol-

ecule release are thermoresponsive hydrolysis of block copolymers hydrogels and
full dissociation of polycationic poly(allylamine) hydrochloride and polyanionic
polystyrene sulfonate complex microgel during increase pH (Buwalda et al. 2014;
Rondon et al. 2014). A growing demand for hydrogel-based drug delivery since
1980 onwards shows increasing treads (Fig. 9.8).
This section focuses on hydrogels obtained from natural polymers. It out-
lines the structure and function of natural polymeric hydrogels in the area of
Pharmaceutics-based drug delivery. The distinct sub-classification of a less com-
mon form of hydrogels, known as microgels, explains this difference. Also,
another area of this review focuses on the physico-chemical properties of hydro-
gels as a drug delivery system with ideal pharmacokinetic targeting areas.
A hydrogel is a solid or semi-solid hydrophilic matrix comprising of polymeric
macromolecules crosslinked by varying combinations of hydrogen bonding, Van
der Waals, ionic electrostatic-based and covalent-based intermolecular interac-
tions (Laftah et al. 2011; Huang et al. 2007). Hydrogels possess matrix swelling
or shrinkage properties in physico-chemical solvent media such as pH, tempera-
ture and ionic strength of electrolytes in solution (Chang et al. 2010; Li et al.
2014b). Usually, solvent ion concentrations at medium ionic strengths allow for
ion exchange between polyelectrolyte gel and solvent ions resulting in osmotic
pressure increases inside hydrogel and thus causing swelling (Richter et al. 2008).
Polymeric hydrogels such as N-isopropylacrylamide (NIPAAm) are influenced
by higher ionic strength of electrolytes and temperature in solution and they can
swell above their critical solution thresholds (Dίez-Peña et al. 2002; Sharpe et al.
2014). NIPAAm has swelling properties as the nitrogen groups’ hydrogen bond
with water at NIPAAm lower critical solution temperature of 34 °C (Lee and Fu

6000
5500
5000
Number of publications

4500
Hydrogel drugs (1975 to 2014)
4000
3500
3000
2500
2000
1500
1000
500
0
75 ≤ y ≤ 79 80 ≤ y ≤ 84 85 ≤ y ≤ 89 90 ≤ y ≤ 94 95 ≤ y ≤ 99 00 ≤ y ≤ 04 05 ≤ y ≤ 09 10 ≤ y ≤ 14
Year Range

Fig. 9.8  The number of hydrogel drug publications according to year range (Web of Science)
9  Pharmaceutical Applications of Natural Polymers 289

2003). Also the deprotonation of carboxylic acid groups in hydrogels such as

polyacrylic acid (polyAA) and interpenetrating network of chitosan combined
poly(sodiumacrylate-co-hydroxyethyl methacrylate) (SCPSC) in high pH results
in ionic repulsion and induces swelling (Fig. 9.9) (Yang et al. 2011; Mandal and
Ray 2014).
The equilibrium swelling ratio of SCPSC was significantly 1.6 folds greater in
pH 7 buffer medium when compared with pH 3.9 (Mandal and Ray 2014). The
polymeric macromolecules in hydrogels can be cationic, anionic or entirely neu-
tral with regard to interacting with another macromolecule or drug molecules (Van
Vlierberghe et al. 2011; Singh and Lee 2014). The crosslinking of hydrogels com-
bines highly desirable characteristics such as mechanical strength, pseudoplas-
ticity, drug and macromolecular intermolecular interactions and plasma swelling
(Zhao et al. 2014; Kurland et al. 2014). The porosity of the crosslinked hydrogel

Fig. 9.9  A schematic representation of swelling according to a pH with a hydrogels such as

crosslinked azo polyacrylic acid (pAA) (Adopted from Yang et al. 2011). b Temperature with
hydrogels such as PNIPAM with PNIPAM/IA (Adopted from Yang et al. 2011) with permission
from Royal Society of Chemistry Licence number 3631871241621
290 A. Nayak et al.

matrix determines aqueous solvent adsorption and rate of drug release (Hoare and
Kohane 2008). However, the insolubility of hydrogels to water is attributed to the
networking arrangement of crosslinks between polymer chains thus maintain-
ing physical structure (Gupta et al. 2002). Nevertheless control in the polymeric
swelling release rates of drugs with possible subsequent degradation of hydrogels
is very much a sought after challenge in matching the duration of drug release
across a therapeutic range and target specificity in the body. There are constraints
and possible major limitations in stabilising porous combination of polymers in
defined mass ratios in attaining desirable controlled release of drug molecules.
However, the complex chemical structures of hydrogels can pose challenging in
synthesis coupled with mass reproducibility and end product purification (Martín
del Valle et al. 2009). Although synthetic polymers seem to have largely dom-
inated over natural polymers in the past decade due to their relatively long ser-
vice life, high water absorption capacity and gel strength and the possibility of
tailored degradation and functionality, natural polymers are highly sort after for
their biocompatibility, availability and low cost. (Ahmed 2015). Hydrogels from
natural source usually require inclusion of synthetic components as, for example
crosslinkers or the hydrogel could be a blend of both natural and synthetic poly-
mers for improved functionality, degradation or biocompatibility (Kamoun et al.
2015). In the following sections we look at some common natural polymers and
their recent applications as hydrogels.

9.8.1 Hydrogels in Transdermal Patches

The architecture of a transdermal patch comprises a drug reservoir or a polymer-

drug matrix trapped between two polymeric layers as a laminated layer-by-layer
arrangement (Sarkar et al. 2014). A study of the effect of mucilage derived from
indigenous taro corns combined with hydroxypropylmethylcellullose (HPMC) was
a patch vehicle in the slow IV drug release of an antihypertensive drug, Diltiazem
(Sarkar et al. 2014). Patches have been developed for targeting the drug molecules
through full skin thickness passive diffusion in the systemic circulation so that
receptors or pathogens in the body are affected by the drug (Suksaeree et al. 2014;
Arkvanshi et al. 2014). A cellulose polymer derived from bacteria, plasticised with
glycerol using solvent evaporation techniques as a potential patch demonstrated
a reduced lidocaine permeation flux in skin epidermis when compared with a
hydroxypropylmethylcellulose gel (Trovatti et al. 2012). The observation of a low
permeation flux is an example of implementing further optimisation-based stud-
ies by using chemical penetration enhancers effecting SC barrier properties at pos-
sible higher concentrations. Proprietary patches available as pharmaceuticals are
Nicorette® (Nicorette.co.uk) in nicotine delivery to wean addiction, Ortho Evra®
(Orthoevra.com) in norelgestromin/ethinyl estradiol delivery to decrease blood
levels of gonadotrophins and inhibiting ovulation and chances of pregnancy and
9  Pharmaceutical Applications of Natural Polymers 291

Exelon®Patch (Novartis.com) in rivastigmine delivery to inhibit cholinesterase by

reversible inhibition in delaying the progression of Alzheimers disease. Those pro-
prietary patches mentioned are examples outlining three completely different ther-
apeutic before current growing trends emerged since the 1980s (Wiedersberg and
Guy 2014). The major benefits of patch-based delivery are reduction in adverse
effects such as gastrointestinal disturbances caused by high dose oral rivastig-
mine as compared with a rivastigmine patch (Reñéa et al. 2014), reduction in peak
plasma concentrations and interventions of prior dose adjustments periodically
from oral and fast intraveneous delivery (Reñéa et al. 2014; Arkvanshi et al. 2014).
The sensitivity of patient’s skin to transdermal patches is a major concern because
of the likelihood of allergic reactions if the patched skin area is left covered for a
long duration (Reñéa et al. 2014).

9.8.2 Nanoparticles for Controlled Delivery

The controlled release of active drug molecules sustained at therapeutic thresh-

olds in specific targets of the body according to the length of treatment is a major
focus in pharmaceutics research (Soppimatha et al. 2001; Ashley et al. 2014). A
significant gap for nanoparticle mediated drugs to enter the pharmaceutical drugs
market exists because of the sophisticated pathological targeting mechanisms and
therefore traditional pharmacology cannot distinctly characterise nanoparticle
drugs (Brambilla et al. 2014). Themoresponsive Poly(NIPAAm-co-AAm) hydro-
gels were shown to have a z-diameter of 156.0 nm after encapsulating gold-silica
nanoparticles and forming nanoshells by collapsing to absorb the gold-silica at
40–45 °C at 780 nm (Strong et al. 2014). A chemotherapeutic agent, doxorubicin
was loaded into the Poly(N-isopropylacrylamide-co-Acrylamide) Poly(NIPAAm-
co-AAm) nanoshells by 1.12 folds greater than without nanoshells arrangement
(Strong et al. 2014). The crosslinkers in NIPAAm-co-AAm hydrogels can revers-
ibly collapse into a dehydrated globular conformation above their lower critical
solution temperature, normally above physiological body temperatures, to release
the drug (Sershen et al. 2000; Fundueanu et al. 2013). Poly(NIPAAm-co-AAm) is
a synthetic polymer. Nevertheless Poly(NIPAAm) has been commonly crosslinked
with natural chitosan because of pH sensitive properties of the amino groups (Li
et al. 2009). The cytotoxicity of Poly(NiPAAm-co-chitosan) containing 5 mg/
ml NIPAAm nanoparticles encapsulated with paclitaxel resulted in 60 % viabil-
ity of human lung cancer cells thus proving favourable toxicity (Li et al. 2009).
Complementing the 60 % cell viability, the cumulative release of Paclitaxel was
increased by 1.86 fold in extracellular tumour conditions of pH 6.8 compared
with pH 7.4 at the same physiological temperatures (Li et al. 2009). Nanoparticle
drugs are usually between 10 and 200 nm in size with generally high efficacies
(Noble et al. 2014). Liposomes are mainly natural phospholipids nanoparticles
as highly advantageous drug delivery vehicles because of the potential to deliver
292 A. Nayak et al.

hydrophobic drugs and biocompatible properties (Noble et al. 2014). Liposomal

synthesised PEG nanoparticles loaded anti-cancer carfilzomib allowed the inhi-
bition in tumour growth and subsequently proved to be up to fourfolds more
cytotoxic to tumours compared with unloaded carfilzomib (Ashley et al. 2014).
Liposomes synthesised with PEG prevents any aggregation of nanoparticles and
adsorption of plasma-based serum proteins that promote immediate clearance
(Noble et al. 2014). The advantage of drug nanoparticles in drug therapy is the
reduction in systemic toxicity and greater drug loading in nanospheres (Ashley
et al. 2014). A huge vacuole still remains for research into drug hydrogel nanopar-
ticles containing higher concentrations of ideal naturally sourced polymers.

9.8.3 Hydrogels for Wound Dressing

Wound dressing is an immediate first aid response in superficial and chronic skin
wounding injuries. The general treatment of skin wounds is to minimise scarring,
microbial infection, pain, protection from further trauma and absorption of excess
exudates from open lacerations (Mayet et al. 2014). Conventional gauzes and pads
based on cotton and synthetic rayon polyester bandages need regular changing
and tend to be more expensive than modern dressings (Boateng et al. 2008). Also
conventional bandages are known to keep the wound bed dry and slow down the
natural skin healing process due to restricted new cell migration and healthy tis-
sue removal when bandage requires changing (Boateng et al. 2008; Rolstad et al.
2012). Hydrogels are an ideal dressing material for absorbing excess exudates,
allowing enough moisture of the wound bed and filling irregular-shaped wound
cavities (Lee et al. 2014; Tran et al. 2011). A synthesised gelatine-hydroxyphe-
nylpropionic acid hydrogel was studied because of well-known biocompatible and
tissue adhesive properties (Lee et al. 2014). A gelatine-hydroxyphenylpropionic
acid hydrogel loaded with human dermal fibroblast resulted in a 1.9 fold wound
closure in mice compared with phosphate buffer solution control after four days
(Lee et al. 2014). The focus on hydrogels for wound dressing may seem irrelevant
in the area of traditional pharmaceutics as defined in the section Portals of drug
administration in the human body. The importance of a new area of study relating
to emergency trauma shows the need for the application hydrogels compounds.

9.8.4 Polymeric Crosslinking in Hydrogels

An important characteristic of a hydrogel is the polymeric strand crosslinking.

Crosslinking of hydrogels with morphologically cross-hatched or entangled mac-
romolecular architecture allows a 3D structure and avoids immediate dissolu-
tion of separate macromolecular strands in hydrophilic solvent (Hennick and van
Nostrum 2012).
9  Pharmaceutical Applications of Natural Polymers 293

Physical crosslinking of polypeptides are attributed to ionic bonding, hydrogen

bonding and hydrophobic interactions in aid of bipolymeric crosslinking (Nonoyama
et al. 2012; Hu et al. 2010). Physically crosslinked hydrogels are inhomogeneous
due to more than one type of intermolecular-based interaction (Hoffman 2002).
Chemically crosslinked hydrogels involve covalent linkages in bridging two
different polymeric strands and the use of crosslinking agents that can react
with specific functional groups in polymeric macromolecules (Hennick and van
Nostrum 2012). Chemically crosslinked hydrogels permit bigger volume increases
during sol-gel transition than physically crosslinked hydrogels (Jonker et al.
2012). The use of chemical crosslinking agents to bind-specific functional groups
for crosslinking polymers is shown in Table 9.2. The process and target applica-
tion of hydrogel and microgel polymers is outlined in Table 9.3.

9.8.5 Natural Polymers in Hydrogels

Polysaccharides such as hyaluronic acid, chondroitin sulphate, chitosan, carboxy-

methylcellulose, hydroxypropylmethylcellulose, methylcellulose, bacterial cellu-
lose and sodium alginate are common examples of carbohydrate derived polymers
in hydrogels (Van Vlierberghe et al. 2011). Examples of proteins used in hydro-
gels include gelatine, collagen, elastin, ovalbumin, β-lactoglobulin and silk fibroin
from both plant and animal sources (Jonker et al. 2012). Polymer strands from nat-
ural, synthetic and partially synthetic sources are acquired as drug delivery vehi-
cles (Gupta et al. 2002). Polypeptides have straight chained or helical assemblies
in their gross macromolecular arrangement such as β-pleated sheets and α-helix
respectively (Woolfson 2010). Amino acids in polypeptides, containing Ala, Glu,
Lys and Gln occur more in α-helices compared with Thr and Val in β-pleated
sheets, in-conjunction to Gly and Pro usually located in the turn area of mol-
ecule (Woolfson 2010). Two hydrophobic regions in the macromolecular struc-
ture of anti-parallel conformation assemble to form the β-pleated sheet (Fig. 9.10)
(Nonoyama et al. 2012; Woolfson 2010). Polypeptide structure hydrogels overall
are the most suitable in mimicking natural extracellular crosslinking matrix (Yao
et al. 2014).
Hyaluronic acid (HA)-based hydrogel particles have been investigated for drug
delivery using trimethoprim (TMP) and naproxen as model drugs. Hyaluronic
acid was modified with an aqueous solution of sodium bis (2-ethythexyl) sulfo-
succinate (AOT)-Isoctane microemulsion system. This formed hyaluronic acid
particle which were further modified by oxidizing to aldehyde (HA-O) using treat-
ment with NaIO4 followed by reacting with cysteamine thus forming thiol ligands
onto the surface of the HA particles. The final HA-based hydrogel particles were
formed by radical polymerization of the HA particles with anionic and cati-
onic monomers 2-acrylamido-2-acrylamido-2-methyl-propanosulfonic acid and
3-acrylamidopropyl-trimethyl-ammonium chloride, respectively. The HA-based
hydrogel particles derived demonstrated good pH dependent size variation and
 294

Table 9.2  Chemical agents for the chemical crosslinking of functional groups in hydrogels

Crosslinker Functional gps Reaction or functional gp Chemical reaction conditions
interactions
Glutaraldehyde (Berger et al. 2004; Di-aldehydes (Berger et al. 2004) Imine group formed by Schiff No heat required and slow addition is
Costa-Júnior et al.2009) base formation (Berger et al. 2004; usual (Costa-Júnior et al. 2009)
Costa-Júnior et al. 2009). Acetal
group formation from hydroxyl
groups (Costa-Júnior et al. 2009)
Poly(ethylene glycol)–propion Amine (Luo et al. 2000) Azide addition (Luo et al. 2000) Unimolecular addition of PEG-diald
dialdehyde (PEG–diald) (Luo et al. and polymer in ambient temperature
2000) conditions (Luo et al. 2000)
Methylene bis-acrylamide (Berger Acrylamide, ethylene (Berger et al. Variable (Berger et al. 2004)
et al. 2004) 2004; Bhattacharyya and Ray 2014)
Genipin (Song et al. 2009; Amino acid groups and secondary Amino acid groups (Song et al. Set pH conditions (Muzzarelli 2009)
Muzzarelli 2009) amino group in acidic and neutral 2009). Condensation reactions in
pH (Muzzarelli 2009) acidic or neutral conditions and
aldol condensation in basic conditions
(Muzzarelli 2009)
A. Nayak et al.
Table 9.3  Recent examples of hydrogels developed in drug delivery
Polymer Composition Processa Target/deliverya Reference(s)
Casein 100 % Temperature-based gelation BSA molecule into buffered Song et al. (2009)
solution
Poly(N-isopropylacrylamide- NIPAAm and AAm, 83.3:16.7 Poly(NIPAAm-co-AAm) syn- Propranolol and lidocaine Fundueanu et al.
co-Acrylamide) (% mol ratio) thesis: free radical copolymeri- (2009)
poly(NIPAAm-co-AAm) sation with AIBN initiator.
Microsphere process: W/O
emulsification and copoly-
mer solubilised by acidic DI
water and crosslinking using
glutaraldehyde
Alginate (Monomer unit: Methacrylated alginate Photocrosslinking of meth- Bovine chondrocytes for Jeon et al. (2009)
1,4-linked b-d-mannuronic (5.7–45.3 %) acrylated alginate at 365 nm ­cytocompatibility for cell
acid and a-l-guluronic acid) and 0.05 % w/v Irgacure culture
9  Pharmaceutical Applications of Natural Polymers

D-2959 photo initiator

Sodium carboxymethylcellulose NaCMC: cell (5:5–9:1 by wt). Solubilisation of cell and In vitro release of Bovine Chang et al. (2010)
(NaCMC): cellulose A hydrogel film NaCMC and crosslinking with Serum Albumin (BSA)
epichlorohydrin (ECH)
Poly(ethylene oxide)- GZm/PF127 molar ratio from Esterification between carboxyl BSA, glucoprotein rKPM-11 Moreno et al. (2014)
poly(propylene oxide)- 1 to 20 (GZm is the monomer, groups of maleic anhydride and dextran in PBS (pH 7.4)
poly(ethylene oxide) (PF127) methyl vinyl ether-co-maleic and hydroxyl groups of PF127.
and Poly(methyl vinyl ether-co- anhydride) Subsequent solvent evaporation
maleic anhydride) (GZ) of tetrahydrofuran followed by
precipitate copolymer filtration
and collection
aThe process are the main experimental conditions, reagents or crosslinking reagents in preparing hydrogels. The target/delivery is the active molecule or
drug studied for encapsulation or controlled release from hydrogel
295
296 A. Nayak et al.

Fig. 9.10  An anti-parallel orientation for a β-pleated sheet (Adopted from Woolfson 2010)

swelling properties. This is important for applications such as controlling and tun-
ing the rate of drug delivery in different parts of the body. This takes advantage of
the remarkable ability of HA to demonstrate variety of swelling kinetics in differ-
ent pH environment (Burke and Barrett 2005; Ekici et al. 2014). Other natural pol-
ymers which tend to form hydrogels with pH dependent swelling kinetics include
alginate. Arginine grafted alginate hydrogels are also potential carriers for protein
drugs enabling oral delivery. This can be used to orally deliver proteins while lim-
iting the effect of metabolism in the gastrointestinal tract prior to reaching the tar-
get area (Eldin et al. 2014).
Nanocellulose has had increasing application in the pharmaceutical area in
recent times. Current interests in exploring the industrial application of nanocel-
lulose extend to their use as hydrogels for drug delivery. Nanofibrillar cellulose
derived from wood pulp was developed into injectable hydrogel for localised and
controlled release of large and small compounds in vivo. Although further stud-
ies are required to establish the nature and possibility of interaction between the
hydrogel material and the active drug, studies carried out so far show that nanofi-
brillar cellulose has good potential as an injectable hydrogel drug delivery system.
This application exploits the shear thinning property of nanofibrillar cellulose
hydrogel which makes it possible to inject with ease using a syringe while still
maintaining its viscosity (Bhattacharya 2012). This allows for localised and tar-
geted delivery to easily assessable regions using injections. Nanofibrillar cellu-
lose hydrogel also has the advantage of ease of preparation without need for an
external source of gel activation unlike most other hydrogels being explored for
the same application. The external activators could be chemicals or irradiation
methods which could invoke toxicity or complication of the delivery process.
Nanofibrillar cellulose-based hydrogels, however possess intrinsic pseudoplastic-
ity which makes them suitable an injectable hydrogels (Laurén et al. 2014).
Chitosan and its various derivatives have also been expired as hydrogels for
drug delivery. Due to the robust chemical property, chitosan can be crosslinked
using a crosslinker such as genipin and glutaraldehyde with a variety of other nat-
ural polymers to obtain desired functionality. For example, chitosan is crosslinked
with gelatin for improved rigidity and with starch for improved flexibility and
cohesion (Giri et al. 2012).
Cellulose is a highly abundant natural polymer in plants, bacteria, algae and
fungi phylum. The unbranched chains consist of 1,4 glycosidic linkage of mon-
omer units, d-glucopyranose (DGP) and presence of three hydroxyl groups per
9  Pharmaceutical Applications of Natural Polymers 297

DGP monomer (Kamel et al. 2008; Carter Fox et al. 2011). Cellulose polymers
consist of amorphous and crystalline arrangements in which the hydrolysis proper-
ties of cellulose are found to be more unfavourable in higher crystalline arrange-
ments (Walker and Wilson 1991).
Sodium Carboxymethylcellulose (NaCMC) is a cellulose derived water soluble
polymer (Sannino et al. 2009). NaCMC is grossly anionic because of the nega-
tive electron density with respect to the carboxymethyl substitution region. Hence,
polyanionic NaCMC has the potential to electrostatically interact with gelatine
below its isoelectric point (Devi and Kumar 2009). NaCMC and gelatine are bio-
compatible as NaCMC is biologically excreted and gelatine is degraded by natu-
ral enzymes (Rathna and Chatterji 2003). NaCMC is able to hydrogen bond with
water molecules hence hydrogel NaCMC crosslinked gelatine possesses swell-
ing properties which is reported by Tataru et al. (2011). Individual polymers of
NaCMC and gelatine have the tendency to swell in ambient temperature water. As
far as we know there is no published literature comparing swelling rates of indi-
vidual NaCMC and gelatine with post bipolymeric NaCMC: gelatine microgel.
Ionic interactions are dominant intermolecular forces in crosslinking polyanionic
NaCMC with polycationic polymers such as polyvinylamine (PVAm) (Chang and
Zhang 2011). The degree of substitution (DS) defines this structure when hydroxyl
groups in the glucopyranose monomer are replaced with carboxymethyl groups
in which the number of substituted hydroxyls accounts to the degree of substitu-
tion (Rokhade et al. 2006). The higher the DS and quite significantly the lower
the MW of NaCMC allows for increased in ionic conductivity (Lee and Oh 2013).
The discharge capacity of NaCMC (0.9 DS and 250 kDa) up to 0.5 current den-
sity (C-rate) was 165 mAh g−1 compared with NaCMC (0.9 DS and 700 kDa)
at 155 mAh g−1 (Lee and Oh 2013). Potentiometric titration with hydrochloric
acid as a carboxylate proton donor coupled with Infrared spectroscopy in know-
ing the relative amount of carboxyl groups is implemented in calculating DS
(Pushpamalar et al. 2006).
Gelatin is another natural polymer which finds wide application as hydrogels
for drug delivery. Hydrogel made from gelatin and polyvinyl alcohol (PVA) has
been developed for application in delivery of anti-cancer drug Cisplatin. The
anti-cancer drug encapsulated within the macrocycle cucurbit(7)uril was incorpo-
rated in hydrogel formulations containing between 0 and 4 % PVA. The hydro-
gel formed demonstrated a controllable swelling and degradation rate which was
PVA concentration dependent. As the concentration of PVA in the hydrogel for-
mulation increases, the release rate of encapsulated drug decreases such that the
release rate of the drug can be controlled by varying the concentration of the PVA
in the hydrogel formulation. Hydrogel containing gelatin only inhibited cancer
cell growth by 80 % while hydrogel containing 2 % PVA inhibited cell growth by
4 %. At 4 % cell growth inhibition was 20 %. When compared to intraperitoneal
injection of free cisplatin at high dose of 150 µg, subcutaneous implantation of the
gelatin PVA hydrogels at just 30 µg of cisplatin achieved the same effectiveness
such that the use of the gelatin/PVA hydrogel improved the effectiveness of the
anti-cancer drug (Oun et al. 2014).
298 A. Nayak et al.

A globular whey protein of high abundance from cow’s milk is β-lactoglobulin

which has the potential in binding hydrophobic molecules via hydrogen bond-
ing and van der Waals interactions (Livney 2010; Lee and Hong 2009). Chitosan
forms a complex coacervates with β-lactoglobulin at pH 6.5 (Lee and Hong 2009).
Pectin which is an anionic polysaccharide coacervates with β-lactoglobulin and
has an apparent mean particle diameter below 1000 nm and zeta potential reaching
−40 mV above pH 6 for formulations containing pectin 0.5 % w/w (Jones et al.
2009). Here, very low zeta potential values outline particle repulsion and minimal
particle aggregation (Jones et al. 2009). As far as we know there is currently stud-
ies performed in the encapsulation and release of drugs using β-lactoglobulin as a
co-polymer in a hydrogel.

9.8.6 The Preparation Techniques of Hydrogels

There are numerous valid engineering techniques in the preparation of natural

hydrogels. Natural polymers such as gelatin, κ-carrageenan, agarose and gellan
gum in hot solutions undergo random coil to helix transitions with the support of
ionic salts such as Na+ which lowers the repulsive forces between same electro-
static charges, allowing ionic interaction and the polymeric crosslinking to occur
(Fig. 9.10) (Coutinho et al. 2010; Gulrez et al. 2011). The polymer κ-carrageenan
can further form a superhelical network when a number of helices aggregate in the
presence of ions and a gel is formed (Viebke et al. 1994).
Polymers possessing charged functional groups such as chitosan, carboxym-
ethylcellulose, gellan, gelatin, alginates and pectin can be crosslinked with mul-
tivalent ions of opposite charges, which is known as ionotropic gelation (Patil
et al. 2012). Polyanionic molecules such as alginic acid and l-carrageenan can
be reversibly crosslinked by cations such as Ca2+, Zn2+ and Fe3+ (Bracher et al.
2010; Agulhon et al. 2012). An ionotropic crosslinking interaction between a diva-
lent cation and polyanionic groups between two chains of sodium alginate is by
chelate complex with glucuronic acid groups (Fig. 9.11) (Ahirrao et al. 2014).

Fig. 9.11  Illustration of random coil to helical transition of anionic, natural polymers, e.g. gel-
lan gum during the cooling of a hot polymeric solution
9  Pharmaceutical Applications of Natural Polymers 299

A recent study by Boppana et al. (2010) combined polyanionic sodium carbox-

ymethylcellulose with polycationic albumin via Al3+ ions to induce electrostatic
interactions by ionotropic gelation prior to chemical crosslinking using glutaralde-
hyde. The entrapment efficiency of a drug, simvastatin, was between 74 and 82 %
in a bipolymeric sodium carboxymethylcellulose and albumin hydrogel network
(Boppana et al. 2010). Slightly different to ionotropic gelation, a process known
as complex coacervation involves the electrostatic attraction of oppositely charged
polyelectrolytes such as precipitate or gel in solution because of change of factors
such as pH, ionic strength and polymeric mass ratios (Jin and Kim 2008; Hoffman
2002). An alginate/β-lactoglobulin lipid droplets contained in hydrogel matrices
were complex coacervated with alginate (–NH3+) and cationic chitosan (–COO–)
at acidic pH ranges of 3.5–6.5 in the formation of beads for gastrointestinal active
molecule delivery (Li and McClements 2011). An example of a complex coacer-
vate bipolymer is sodium carboxymethylcellulose and gelatin in the formation of a
complex coacervate.
Chemical crosslinking of two non-ionic polymers can be enzyme catalysed
in the addition of a crosslinking agent forming covalent bonds on specific func-
tional groups in forming a hydrogel (Hoare and Kohane 2008; Hennick and van
Nostrum 2012). An example is a crosslinker, 1, 2, 3, 4-butanetetracarboxylic dian-
hydride (BTCA) forming ester linkages with the hydroxyl groups on β-mannose or
α-galactose monomers present in guar gum with enzyme, 4-dimethylaminopyri-
dine (DMAP) (Fig. 9.12) (Kono et al. 2014).
Monomers of low molecular weight can undergo radical polymerisation using
photoinitiators forming photopolymerised hydrogels such as dextran and gly-
cidyl acrylate (Hennick and van Nostrum 2012; Nguyen and West 2002). The

Fig. 9.12  Schematic outlines in the preparation of hydrogels. a An ionotropic interaction formed

by chelation between Ca2+ and alginic acid (Adopted from Ahirrao et al. 2014). b Chemical
crosslinking of guar gum with BTCA crosslinking agent and enzyme. Reused under creative
commons attribution licence
300 A. Nayak et al.

advantages of photopolymerisation are rapid curing rates during processing, lower

production of heat and spatial and temporal control of process polymerisation
reactions (Nguyen and West 2002; Burdick and Prestwich 2011). Hyaluronic acid
is radically polymerised with methacrylic anhydride under basic conditions in pro-
ducing methacrylated hyaluronic acid (Burdick and Prestwich 2011).
The manufacturing considerations in bulk production of hydrogels of bead
morphology use microengineering processes in attempting to optimise control
and batch wise consistency requirements. Micromoulding is an engineering pro-
cess recently employed in the production of hydrogel microneedles composed of
NIPAAm particles suspended in 50/50 polylactic-co-glycolic acid (PLGA) (Kim
et al. 2012). The micromould implemented in the fabrication of NIPAAm hydro-
gel microneedles were poly-di-methyl siloxane and molten PLGA was added
to pre-filled NIPAAm particles in the mould followed by curing at 150 °C and
−100 kPa pressure in a vacuum oven (Kim et al. 2012). Microfluidics is a spe-
cialist area concerned with the fluid dynamics and engineering of micron scale
confinement of flowing fluids (Domachuk et al. 2010). A phospholipid polymer,
poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate
(BMA)-co-4-vinylphenyl boronic acid (PMBV) and poly (vinyl alcohol) (PVA)
were crosslinked with the aid of a microfluidic device (Fig. 9.13) (Aikawa et al.
2012). The PMBV and PVA were separately injected and droplets were pinched
off after gelation induced by contact, the flow rate ratio between paraffin oil and
polymer was high in order to decrease the diameter of hydrogel droplets (Aikawa
et al. 2012).
The main disadvantage of microfluidics is the possibility of channel clogging
due to gelation of gel beads when external gelation by ionotropic crosslinking is
adopted (Mark et al. 2009). Photolithography implements a source of radiation,
usually UV, directed onto the fluid material containing a photoinitiator in propa-
gating crosslinking reactions according to polymerisation kinetics via trans-
parent areas of the photomask that outline the pattern (Fig. 9.14) (Helgeson
et al. 2011).

Fig. 9.13  Microfluidic
device in the generation
of hydrogel microparticles
of PMBV/PVA (Adopted
from Aikawa et al. 2012)
reused with permission
from American Chemical
Society Licence number
3631861429984
9  Pharmaceutical Applications of Natural Polymers 301

Fig. 9.14  Outline of photolithography for a polymeric hydrogel (reproduced from Helgeson

et al. (2011) with permission from Elsevier, licence number 3631910827880

Hydrogels made photoresponsive can evoke changes in degree of swelling,

shape, viscosity or elasticity properties (Tomatsu et al. 2011). They are function-
alised as photoresponsive when a polymer is modified with supramolecular inter-
acting groups, formation of photoresponsive low molecular weight gelators into
a supramolecular hydrogel and addition of photoresponsive groups in hydrogel
modification (Tomatsu et al. 2011). A recent study by Xiao et al. (2011) fabri-
cated methacrylated gelatine and silk fibroin interpenetrating polymer network
hydrogels using 2-hydroxy-1-[4-(hydroxyethoxy)-phenyl]-2-methyl-l-propanone
(Irgacure 2959) as the photoinitiator under UV radiation. The mass ratios of crys-
tallised silk fibroin crosslinked with methacrylated gelatine defined the mechani-
cal stiffness and the rate of degradation (Xiao et al. 2011). Photolithography and
micromoulding require a lot of capital investment relating to the precision fabrica-
tion of photomasks, photocrosslinking reagents and moulds (Mark et al. 2009).
Membrane emulsification involves injection of the dispersed phase through a
microporous membrane into the continuous phase of an immiscible liquid under
pressure. The purpose of membrane emulsification is to obtain monodisperse par-
ticles from controlled membrane pore size and pore size distributions for average
emulsion diameters (Akamatsu et al. 2010). Chitosan-coated calcium alginate
particles with a diameter of 4.4 μm were produced from a w/o emulsion using
Shirasu porous glass (SPG) membranes (Akamatsu et al. 2010).

9.8.7 Microgels

Microgels are hydrogel microparticles that are colloidally stable in aqueous solu-
tions (Gao et al. 2014; Vinogradov 2006). Temperature-responsive microgels
undergo a rapid change in hydrodynamic particle diameters in temperature-based
hydrating or dehydrating polymers in aqueous solution at the lower critical solu-
tion temperature (Yang et al. 2013). Techniques for the preparation of hydrogels
can be copied or adopted for microgels as long as there is no non-particulate mor-
phology such as film or deviation towards a pure polymeric formulation. There are
three important factors in using microgels in drug delivery. The first factor con-
cerns the stability of microgels as a stable dispersion in physiological conditions
mimicking blood plasma because the microgel drug has to circulate systemically
302 A. Nayak et al.

before significant controlled release of the drug (Oh et al. 2008; Pich and Adler
2007). The second factor is the degradation kinetics in allowing sustainable release
leading to clearance after complete degradation of the microgel (Oh et al. 2008).
The third factor is controlling the microgel particle diameter to less than 200 nm in
diameter to pass blood vessels or enter cells membranes (Oh et al. 2008).

9.8.8 Microgels from Natural Polymers in Drug Delivery

Current research in formulating and pharmacokinetic-based testing of microgel

drugs is still being pursued. Most recently, plasmid DNA macromolecules were
loaded in microgels by an inversion microemulsion polymerisation technique with
ethylene glycol diglycidyl ether (EGDE) crosslinking reagent for cancer research
therapy (Costa et al. 2014). A novel pH sensitive microgel was prepared using a
salt bridge interaction between polyanionic carboxymethylcellulose (CMC) and
tertiary amide of cationic (2-hydroxyethyl) trimethylammonium chloride benzo-
ate (TMACB) linked with β-Cyclodextrin (β-CD) at pH 8.0 (Yang and Kim 2010).
β-CD was crosslinked with CMC using TMACB and a model drug, calcein was
loaded successfully (Yang and Kim 2010).

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Chapter 10
Environmental Impact of Natural Polymers

Witold Brostow and Tea Datashvili

10.1 Introduction

In 1920, the Nobel laureate Hermann Staudinger recognized that natural and
man-made polymers are produced according to the same blueprint: a very large
number of small monomer molecules are linked together to produce high-molec-
ular-weight macromolecules (Staudinger 1920). In both natural and man-made
technologies, polymers play a prominent role as extraordinarily versatile and
diversified structural and multifunctional macromolecular materials (Brostow
2000, 2009). Properties are readily tuned by varying monomer type, sequence of
monomer incorporation, polymerization processes, polymer superstructures, and
processing technologies (Abdel-Azim et al. 2009; Estevez et al. 2007; Brostow
et al. 2007; Hagg Lobland et al. 2008; Orozco et al. 2014). Without polymers,
modern life would be impossible because polymers secure the high quality of life
and serve as pace-makers for modern technologies (Brostow et al. 2007, 2010a;
Brostow and Pietkiewicz 2007).
During the early days of polymer sciences and engineering (PSE), almost
all materials were based exclusively upon chemically modified biopolymers.
Examples are sugar-based cellulose which is the major component of biomass,

W. Brostow (*) 
Laboratory of Advanced Polymers and Optimized Materials (LAPOM),
Department of Materials Science and Engineering and Department of Physics,
University of North Texas, 3940 North Elm Street, Denton, TX 76207, USA
e-mail: wkbrostow@gmail.com
URL: http://www.unt.edu/LAPOM/
T. Datashvili 
Innovation and Technology, Braskem Americas, 550 Technology Drive,
Pittsburgh, PA 15219, USA
e-mail: tea.datashvili@braskem.com

© Springer International Publishing Switzerland 2016 315

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_10
316 W. Brostow and T. Datashvili

also wood, while cotton represents the most abundant organic compound produced
by living organisms. In biological cells and biotechnology labs, the incorporation
of 20 amino acids is precisely controlled, producing polypeptides such as spider
silk, wool, enzymes, insulin, and a great variety of other synthetic proteins for
industrial and biomedical applications.
We need to clarify that “green” and “natural” are not equivalent terms. As their
name implies, natural polymers (or biopolymers) are polymers that occur naturally
or are produced by living organisms (such as cellulose, silk, chitin, protein, DNA).
By a wider definition, natural polymers can be man-made out of raw materials that
are found in nature. Although natural polymers still amount to less than 1 % of
the 300 million tons of plastics produced per year, their production is steadily ris-
ing. In the USA, demand for natural polymers has been predicted to expand 6.9 %
annually and rise from $3.3 billion in 2012 to $4.6 billion in 2016 (Freedonia
Group 2012; Transparency market research 2013). The natural polymers market is
driven by a growing demand for natural polymers with pharmaceutical and med-
ical applications. Natural polymers also are used in construction and adhesives,
food, the food packaging and beverage industries, and cosmetics and toiletries, as
well as the paint and inks industries. The market is led by cellulose ethers and also
includes starch and fermentation polymers, exudates and vegetable gums, protein-
based polymers, and marine polymers.
So, what’s Green? Green polymers, on the other hand, are those produced using
green (or sustainable) chemistry, a term that appeared in the 1990s. According to
the International Union of Pure and Applied Chemistry (IUPAC) definition, green
chemistry relates to the “design of chemical products and processes that reduce
or eliminate the use or generation of substances hazardous to humans, animals,
plants, and the environment” (Green Polymer Chemistry 2014). Thus, green
chemistry seeks to reduce and prevent pollution at its source. In fact, many exist-
ing polymers and polymerization processes meet the demands of green chemis-
try. Prominent examples of successful sustainable materials are polyolefins such as
polyethylene and polypropylene, which amount to around half of the global poly-
mer production. Modern olefin polymerization has set new standards for environ-
mentally friendly polymer production. Polymer properties can be readily tuned as
a function of catalyst type and process conditions to meet the demands of specific
applications. Moreover, polyolefins are very effectively recycled either by remold-
ing or by facile thermal cleavage of the polymer backbone. Polyolefins meet the
demands of sustainable development, preserving resources for future generations.
In terms of their favorable ecobalance, recycling, energy-, and resource effec-
tiveness as well as their attractive cost/performance ratio, polyolefins outperform
all biopolymers and bio-based plastics. In principle, it is feasible to switch from
fossil resources to bio-based feedstocks in polyolefin manufacturing to meet the
demands of green chemistry. Today, polyolefin technology stands for the most
effective and sustainable use of oil and gas, especially when compared with burn-
ing oil and gas in energy production. In contrast, most biotechnology processes
consume significant amounts of water, produce byproduct wastes, and require
energy-intensive biopolymer purification.
10  Environmental Impact of Natural Polymers 317

Further, an integral part of the green economy concept is fostering the use of
renewable resources and bio-based products. Environmentalists “dream” of using
solar power in biological photosynthesis to convert greenhouse gas carbon dioxide
and water into biomass, which then serves as a feedstock for biofuels, biopower,
and bioplastics (Fig. 11.1).
From this extremely idealistic point of view, biodegradation appears to solve
the littering problem encountered when highly durable synthetic polymers are not
recycled. However, we have to keep in mind that that “bio” does not imply quan-
titative and rapid degradation to produce exclusively carbon dioxide and water.
Biodegradation can also produce water-soluble and even toxic metabolites that are

Fig.  11.1  Biomass usage and production of the biofuels (Adapted from http://www.our-
energy.com/news/biomass_production_needs_to_become_sustainable.html)
318 W. Brostow and T. Datashvili

washed away by rain and thus pollute groundwater. In landfills, paper made from
cellulose and other in principle biodegradable materials do not degrade and sur-
vive for many decades when oxygen and water are absent. Moreover, biodegrada-
tion and bioerosion render polymers brittle so that they readily disintegrate when
exposed to mechanical stresses. Often, they form very small dust-like micron- and
nanometer-sized particles, which are carried away by wind or rain. Although the
biodegrading plastics are no longer visible to the human eye, the resulting fine and
invisible particles can accumulate in the air and cause inhalation hazards. Most
biodegradable polymers are coveted source of food for bacteria, other microorgan-
isms, for example fungal spores, and even small animals, such as insects, bugs,
mice, and rats.
Let us take a closer look at what drives the green and renewable polymer indus-
tries. According to Rolf Mülhaupt from the University of Freiburg, Germany
(Mülhaupt 2013), the development of the green polymer industry is inevitable:
at the beginning of the twenty-first century, we are experiencing a renaissance
of renewable polymers and a major thrust towards the development of bio-based
macromolecular materials. There are several reasons for this paradigm shift—and
for the envisioned transition from petrochemistry to bioeconomy.
From the economic point of view, the dwindling oil supply is likely to further
boost the oil price, especially in view of the expected surge in worldwide energy
demand. Energy demands are increasing worldwide for the simple reason that the
population of the Earth is increasing at a high rate. This could drastically impact
the cost-effectiveness and competiveness of plastics. Shifting chemical raw mate-
rial production to renewable resources or coal could safeguard plastics production
against this expected new future oil crisis. Hence, another even more important
reason is the growing concerns of consumers regarding global warming, resulting
in a surging demand for sustainable and ‘green’ products. In addition, a tsunami of
environmental legislation and regulations is propelling the development of envi-
ronmentally friendly products with a low carbon footprint.
In the production of polymers, green principles include:
• A high content of raw material in the product
• A clean (no-waste) and lean production processes and reducing greenhouse gas
emissions
• Elimination of use of additional substances such as organic solvents
• High energy efficiency in manufacturing
• Use of renewable resources and renewable energy
• Absence of health and environmental hazards
• High safety standards
• Low carbon footprint
• Controlled product lifecycles with effective waste recycling.
In addition, the use of renewable resources for green polymer production should
not compete with food production, should not promote intensified farming or
deforestation, and should not use transgenic plants or genetically modified bacte-
ria; biodegradable polymers should not produce inhalable spores or nanoparticles.
10  Environmental Impact of Natural Polymers 319

There are three basic strategies to produce renewable plastics:

1. Using biomass and/or carbon dioxide to produce ‘renewable oil’ and green
monomers for highly resource- and energy-effective polymer manufacturing
processes
2. Through living cells, which are converted into solar-powered chemical reac-
tors, using genetic engineering and biotechnology routes to produce biopoly-
mers and bio-based polymers
3. By activation and polymerization of carbon dioxide.
Whereas Nature needs more than 300 million years to convert biomass into oil,
there are several options for producing synthetic bio-based renewable oil and even
“green coal” on a large scale that require only a few minutes; biofuel technologies
are developed to refine biomass to produce renewable oil and green monomers.
Inspired by coal liquefaction and gasification, biomass-to-liquid (BtL) conversion
is based on the Fischer–Tropsch process to convert biomass into a mixture of car-
bon monoxide and hydrogen (called syngas), which is an important feedstock for
chemicals. Although the entire plant can be gasified, this process is energy-inten-
sive, especially when producing nonpolar olefin monomers. Less favorable energy
and problematic eco-balances are typical for biodiesel, prepared by transesterifica-
tion of vegetable oils with methanol, accompanied by glycerol byproduct forma-
tion. Among emerging biofuels, bioethanol is produced by fermentation of sugar
obtained from sugarcane or cellulose. Bioethanol represents a very versatile raw
biomaterial for producing olefin and diolefin monomers such as ethylene, propyl-
ene, and butadiene. Both BtL and bioethanol processes involve rather poor atom
economy—because only part of the raw material is incorporated into the polymer
product. There is another option: biomass is directly converted into renewable
coal and oil in a single process step. In the catalytic pressureless liquefaction of
wood and plastics wastes, developed by AlphaKat in Germany, high-quality diesel
fuel is produced without requiring the high temperatures and pressures typical for
coal gasification and the Fischer–Tropsch processes. Several processes have been
developed to convert carbon dioxide into carbon monoxide, methanol, formic acid,
and formaldehyde. In a recent advance, photocatalysis was employed to convert
aqueous carbon dioxide into carbon monoxide using in situ water splitting as a
hydrogen source. Going well beyond the scope of biomass utilization, the direct
chemical fixation of carbon dioxide is commonly recognized as an attractive green
feedstock and green solvent for the chemical industry.

10.2 Market Trends for the Renewable Plastics

Today the world is facing mounting global crises, ranging from global finan-
cial market distress to extreme climate-induced weather events and skyrocket-
ing costs for energy. At present, the world population exceeds 7 billion people
and is projected to reach 9 billion people by 2050; this prediction might be an
320 W. Brostow and T. Datashvili

Fig. 11.2  Integral parts
of sustainable economy
(Adapted from http://www.
education4sustainability.
org/2013/01/)

underestimate. People living in developing countries aspire to the living standards

of the Western world and claim their rightful part of the world’s resources and
plastics production. The resulting drastically increasing hunger for energy, which
is currently satisfied by consuming fossil fuels, will undoubtedly further increase
emissions of the greenhouse gases, water vapor, methane, and carbon dioxide.
In green economy, it is imperative to reduce the demand for resources and
energy, minimize wastes, prevent environmental pollution and hazards, reduce
greenhouse gas emissions, optimize manufacturing processes, and establish effec-
tive recycling of wastes. These elements are an integral part of sustainable chem-
istry, which is also referred to as green chemistry, a term coined in the 1990s
(Fig. 11.2).
Green polymers, renewable polymers, and bioplastics already are more com-
mon than one might think.
Bio-based polymers are closer to the reality of replacing conventional polymers
than ever before. Nowadays, bio-based polymers are commonly found in many
applications from commodity to hi-tech applications due to advancement in bio-
technologies and public awareness. However, despite these advancements, there
are still some drawbacks—which prevent the wider commercialization of bio-
based polymers in many applications. This is mainly due to comparisons of perfor-
mance and price with their conventional counterparts; thus, a significant challenge
for bio-based polymers remains.
We all know about bioethanol as an emerging biofuel, produced by fermenta-
tion of sugar obtained from sugar cane or cellulose (Fig. 11.3).
Bioethanol also is a versatile raw biomaterial for producing olefin and diolefin
monomers, including ethylene, propylene, and butadiene. In 2010, Braskem company
10  Environmental Impact of Natural Polymers 321

Fig.  11.3  General schematic for producing ethanol (Adapted from http://sec.edgar-

online.com/verenium-corp/10-k-annual-report/2008/03/17/Sect.3.aspx)

in Brazil inaugurated a 200 kt/year plant producing green ethylene from sugar cane
bioethanol for the production of green polyethylene, which is 100 % recyclable.
Using processes that are even more energy-efficient, biomass can be directly
converted into renewable coal and oil. Agricultural and forestry wastes already are
used to produce renewable monomers. Processes have been developed to convert
carbon dioxide into carbon monoxide, methanol, formic acid, and formaldehyde.
Vegetable oils can be used to produce biodiesel and glycerol as a byproduct, which
in turn can be used to make a variety of monomers such as propane diol, acrylic
acid, and even epichlorohydrin for the production of epoxy resins.
Carbohydrates, terpenes, proteins, and polyesters are chemically modified and
used in polymer processing and applications. Natural fibers provide excellent fiber
reinforcement for thermosets and thermoplastics. Microfibrillated cellulose is used
in polymer nanocomposites, including applications in medical implants. Lignin
serves as renewable energy source in paper manufacturing, as a filler for cement,
and in various polymers and rubbers. Thermoplastic lignin mixed with natural fib-
ers (Arboform) combines the advantages of wood and synthetic thermoplastics.
Biohybrids has been using starch as a blend component with polyolefins and com-
postable polyesters (Ecoflex). Chitosan and polylactic acid have numerous medi-
cal applications. Casein is used as a binder and as an adhesive.
Renewable monomers are already substituting for “oil-made” monomers.
The ever-present plastic bottles are just one example. In 2011, Coca-Cola Co.
322 W. Brostow and T. Datashvili

announced a goal to make plastic bottles from 100 % bio-based materials.

Recyclable PET “PlantBottles,” which use up to 30 % bio-based monomers, were
introduced in 2009, and can still be recycled.
In spite of this progress, bio-based polymers still hold a tiny fraction of the total
global plastic market. To be specific, biopolymers in 2015 take approximately 1 %
of the total market (Doug 2010). Bio-based polymers offer important contributions
by reducing the dependence on fossil fuels and through the related positive environ-
mental impacts such as reduced carbon dioxide emissions. The legislative landscape
is also changing where bio-based products are being favored through initiatives
such as the Lead Market Initiative (European Union) and BioPreferred (USA). As
a result, there is a worldwide demand for replacing petroleum-derived raw materials
with renewable resource-based raw materials for the production of polymers.
The first generation of bio-based polymers focused on deriving polymers from
agricultural feedstocks such as corn, potatoes, and other carbohydrate feedstocks.
However, the focus has shifted in recent years due to a desire to move away from
food-based resources and significant breakthroughs in biotechnology.
Carbohydrates, terpenes, proteins, and polyesters are prominent representa-
tives of biomaterials that are chemically modified in a variety of ways to meet the
demands of polymer processing and applications.

10.3 Renewable Polymers

Renewable polymers are obtained either from natural biopolymers or by polym-

erization of bio-based monomers. Carbohydrates, terpenes, proteins, and polyes-
ters are prominent representatives of biomaterials that are chemically modified in
various ways to meet the demands of polymer processing and applications; see
Fig. 11.4.
Polylactic Acid
Polylactic acid (PLA) has been known since 1845 but it was not c­ ommercialized
until early 1990 (Erwin et al. 2007). PLA belongs to the family of aliphatic
­polyesters with the basic constitutional unit lactic acid. The monomer lactic acid
is the hydroxyl carboxylic acid which can be obtained via bacterial fermenta-
tion from corn (starch) or sugars obtained from renewable resources. Although
other renewable resources can be used, corn has the advantage of providing a
high-­quality feedstock for fermentation which results in a high-purity lactic acid,
which is required for an efficient synthetic process. l-lactic acid or d-lactic acid is
obtained depending on the microbial strain used during the fermentation process.
PLA can be synthesized from lactic acid by direct polycondensation reac-
tion or ring-opening polymerization of lactide monomer. However, it is difficult
to obtain high-molecular-weight PLA via polycondensation reaction because of
water formation during the reaction. Nature Works LLC (previously Cargill Dow
LLC) has developed a low-cost continuous process for the production of PLA
10  Environmental Impact of Natural Polymers 323

Fig. 11.4  Renewable materials platform (Adapted from http://www.chemengonline.com/renew-

able-feedstocks-trading-barrels-for-bushels/?printmode=1)

(Mülhaupt 2013). In this process, low molecular weight pre-polymer lactide

dimers are formed during a condensation process. In the second step, the pre-
polymers are converted into high-molecular-weight PLA via ring-opening polym-
erization with selected catalysts. Depending on the ratio and stereochemical
nature of the monomer (l or d), various types of PLA and PLA copolymers can be
obtained. The final properties of PLA produced are highly dependent on the ratio
of the d and l forms of the lactic acid.
PLA is a commercially interesting polymer as it shares some similarities with
hydrocarbon polymers such as polyethylene terephthalate (PET). It has many
unique characteristics, including good transparency, glossy appearance, high rigid-
ity, and ability to tolerate various types of processing conditions.
PLA is a thermoplastic polymer which has the potential to replace traditional
polymers such as PET, PS, and PC for packaging to electronic and automotive
applications (Majid et al. 2010). While PLA has similar mechanical properties to
traditional polymers, the thermal properties are not attractive due to its relatively
low glass transition temperature Tg  ≈ 60 °C. This problem can be overcome by
changing the stereochemistry of the polymer and blending with other poly-
mers and processing aids to improve the mechanical properties; varying the ratio
324 W. Brostow and T. Datashvili

of l and d isomer ratio strongly influences the crystallinity of the final polymer.
However, much more work is required to improve the properties of PLA to suit
various applications.
Currently, Nature Works LLC, USA, is the major supplier of PLA sold under
the brand name Ingeo, with a production capacity of 100,000 ton/year. There are
other manufactures of PLA based in the USA, Europe, China, and Japan develop-
ing various grades of PLA suitable for different industrial sectors such as automo-
bile, electronics, medical devices, and commodity applications.
PLA is widely used in many day-to-day applications. It is mainly used in food
packing (including food trays, tableware such as plates and cutlery, water bottles,
candy wraps, cups, etc.). Although PLA has one of the highest heat resistances and
mechanical strengths of all bio-based polymers, it is still not suitable for use in
electronic devices and other engineering applications. NEC Corporation (Japan)
recently produced a PLA with carbon and kenaf fibers with improved thermal and
flame retardancy properties. Fujitsu (Japan) developed a polycarbonate blend with
PLA to make computer housings. In recent years, PLA has been employed as a
membrane material for use in automotive and chemical industry.
The ease of melt processing has led to the production of PLA fibers, which
are increasingly accepted in a wide variety of textiles from dresses to sportswear,
furnishing to drapes, and soft nonwoven baby wipes to tough landscape textiles.
These textiles can outperform traditional textiles made from synthetic counter-
parts. Bioresorbable scaffolds produced with PLA and various PLA blends are
used in implants for growing living cells. The US Food and Drug Administration
(FDA) has approved the use of PLA for certain human clinical applications
(Dorozhkin 2009). In addition, PLA-based materials have been used for bone sup-
port splints.
Polyhydroxyalkanoates
Polyhydroxyalkanoates (PHAs) are a family of polyesters produced by bacterial
fermentation with the potential to replace conventional hydrocarbon-based poly-
mers. PHAs occur naturally in a variety of organisms, but microorganisms can be
employed to tailor their production in cells. Polyhydroxybutyrate (PHB), the sim-
plest PHA, was discovered in 1926 by Maurice Lemoigne as a constituent of the
bacterium Bacillus megaterium (Lemoigne 1923).
PHAs can be produced by varieties of bacteria using several renewable waste
feedstocks. A generic process to produce PHA by bacterial fermentation involves
fermentation, isolation, and purification from fermentation broth. A large fermen-
tation vessel is filled with mineral medium and inoculated with a seed culture that
contains bacteria. The feedstocks include cellulosics, vegetable oils, organic waste,
municipal solid waste, and fatty acids depending on the specific PHA required.
The carbon source is fed into the vessel until it is consumed and cell growth and
PHA accumulation is complete. In general, a minimum of 48 h is required for
fermentation time. To isolate and purify PHA, cells are concentrated, dried, and
extracted with solvents such as acetone or chloroform. The residual cell debris is
removed from the solvent containing dissolved PHA by solid–liquid separation
10  Environmental Impact of Natural Polymers 325

process. The PHA is then precipitated by the addition of an alcohol (e.g., metha-
nol) and recovered by a precipitation process (Kathiraser et al. 2007).
More than 150 PHA monomers have been identified as the constituents of
PHAs (Steinbüchel and Valentin 1995). Such diversity allows the production of
bio-based polymers with a wide range of properties, tailored for specific appli-
cations. Poly-3-hydroxybutyrate was the first bacterial PHA identified. It has
received the greatest attention in terms of pathway characterization and industrial-
scale production. It possesses similar thermal and mechanical properties to those
of polypropylene (Savenkova et al. 2000). However, due to its slow crystallization,
narrow processing temperature range, and tendency to “creep,” it is not attractive
for many applications, requiring further development in order to overcome these
shortcomings (Reis et al. 2008). Several companies have developed PHA copol-
ymers with typically 80–95 % (R)-3-hydroxybutyric acid monomer and 5–20 %
of a second monomer in order to improve the properties of PHAs. Some specific
examples of PHAs include the following:
• Poly(3HB): Poly(3-hydroxybutyrate)
• Poly(3HB-co-3HV): Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV
• Poly(3-HB-co-4HB): Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)
• Poly(3HB-co-3HH): Poly(3-hydroxyoctanoate-co-hydroxyhexanoate)
• Poly(3HO-co-3HH): Poly(3-hydroxyoctanoate-co-hydroxyhexanoate)
• Poly (4-HB): Poly(4-hydroxybutyrate).
The copolymer poly(3HB-co-3HV) has a much lower crystallinity, decreased
stiffness and brittleness, and increased tensile strength and toughness compared
to poly(3HB) while remaining biodegradable. It also has a higher melt viscosity,
which is a desirable property for extrusion and blow molding (Hanggi 1995).
The first commercial plant for PHBV was built in the USA in a joint ven-
ture between Metabolix and Archer Daniels Midland. However, the joint venture
between these two companies ended in 2012. Currently, Tianan Biologic Material
Co. in China is the largest producer of PHB and PHB copolymers. Tianan’s PHBV
contains about 5 % valerate which improves the flexibility of the polymer. Tainjin
Green Biosciences, China, invested along with DSM to build a production plant
with 10 kt/year capacity to produce PHAs for packing and biomedical applications
(DSM Press Release 2008).
PHA polymers are thermoplastic, and their thermal and mechanical prop-
erties depend on their composition. The Tg values of the polymers vary
from  −40 to +5 °C while the melting temperatures range from 50 to 180 °C,
depending on their chemical composition (McChalicher and Srienc 2007). PHB is
similar in its material properties to polypropylene, with a good resistance to mois-
ture and aroma barrier properties. Polyhydroxybutyric acid synthesized from pure
PHB is relatively brittle and stiff. PHB copolymers, which may include other fatty
acids such as beta-hydroxyvaleric acid, may be elastic (McChalicher and Srienc
2007).
PHAs can be processed in existing polymer-processing equipment and can be
converted into injection-molded components: films and sheets, fibers, laminates,
326 W. Brostow and T. Datashvili

and coated articles; nonwoven fabrics, synthetic paper products, disposable

items, feminine hygiene products, adhesives, waxes, paints, binders, and foams.
Metabolix has received US Food and Drug Administration (FDA) clearance
for use of PHAs in food contact applications. These materials are suitable for a
wide range of food packaging applications including caps and closures, dispos-
able items such as forks, spoons, knives, tubs, trays, and hot cup lids, and products
such as housewares, cosmetics, and medical packaging (Philip et al. 2007).
PHAs and their copolymers are widely used as biomedical implant materi-
als. These include sutures, suture fasteners, meniscus repair devices, rivets, bone
plates, surgical mesh, repair patches, cardiovascular patches, tissue repair patches,
and stem cell growth. Changing the PHA composition allows the manufacturer to
tune the properties such as biocompatibility and polymer degradation time within
desirable time frames under specific conditions. PHAs can also be used in drug
delivery due to their biocompatibility and controlled degradability. Only a few
examples of PHAs have been evaluated for this type of applications, and this
remains an important area for exploitation (Tang et al. 2008).
Polybutylene Succinate
Polybutylene succinate (PBS) is an aliphatic polyester with similar properties to
those of PET. PBS is produced by condensation of succinic acid and 1,4-butanediol.
PBS can be produced by either monomers derived from petroleum-based systems
or along the bacterial fermentation route. There are several processes for producing
succinic acid from fossil fuels. Among them, electrochemical synthesis is a common
process with high yield and low cost. However, the fermentation production of suc-
cinic acid has numerous advantages compared to the chemical process. Fermentation
process uses renewable resources and consumes less energy compared to chemical
process. Several companies (solely or in partnership) are now scaling bio-succinate
production processes—which earlier have suffered from poor productivity and high
downstream processing costs. Mitsubishi Chemical (Japan) has developed biomass-
derived succinic acid in collaboration with Ajinomoto to commercialize bio-based
PBS. DSM in the Netherlands and Roquette in France (but with plants also in the
US) are developing a commercially feasible fermentation process for the produc-
tion of succinic acid 1,4-butanediol and subsequent production of PBS. Myriant and
Bioamber have developed a fermentation technology to produce monomers.
Conventional processes for the production of 1,4-butanediol use fossil fuel
feedstocks such as acetylene and formaldehyde. The bio-based process involves
the use of glucose from renewable resources—to produce succinic acid followed
by a chemical reduction to produce butanediol. PBS is produced by transesteri-
fication, direct polymerization, and condensation polymerization reactions. PBS
copolymers can be produced by adding a third monomer such as sebacic acid,
adipic acid, and succinic acid which is also produced by renewable resources
(Bechthold et al. 2008).
PBS is a semicrystalline polyester with a melting point higher than that of
PLA. As usual, its mechanical and thermal properties depend on the crystal struc-
ture and the degree of crystallinity (Nicolas et al. 2011). PBS displays similar
10  Environmental Impact of Natural Polymers 327

crystallization behavior and mechanical properties to those of polyolefin such

as polyethylene. It has a good tensile and impact strength with moderate rigidity
and hardness. The Tg is ≈−32 °C, and the melting temperature Tm  ≈  +115 °C.
In comparison with PLA, PBS is tougher in nature but with a lower rigidity and
Young’s modulus. By changing the monomer composition, mechanical properties
can be tuned to suit the required application.
PBS and their blends have found commercial applications in agriculture, fish-
ery, forestry, construction, and other industrial fields. For example, PBS has been
employed as mulch film, in packaging, and flushable hygiene products and also
used as a non-migrant plasticizer for polyvinyl chloride (PVC). In addition, PBS is
used in foaming. Relatively poor mechanical flexibility of PBS limits the applica-
tions of 100 % PBS-based products. However, this can be overcome by blending
PBS with PLA or starch to improve the mechanical properties significantly, pro-
viding properties similar to that of polyolefins (Eslmai and Kamal 2013).
Bio-polyethylene 
Polyethylene (PE) is an important engineering polymer traditionally produced
from fossil resources. PE is produced by polymerization of ethylene under pres-
sure, temperature, in the presence of a catalyst. Traditionally, ethylene is produced
through steam cracking of naphtha or heavy oils or ethanol dehydration. Microbial
PE or green PE is now being manufactured from dehydration of ethanol produced
by microbial fermentation. The concept of producing PE from bioethanol is not
a particularly new one. In the 1980s, Braskem made bio-PE and bio-PVC from
bioethanol. However, low oil prices and the limitations of the biotechnology pro-
cesses made the technology unattractive at that time (de Guzman 2010).
Currently, bio-PE produced on an industrial scale from bioethanol is derived
from sugarcane. Bioethanol is also derived from biorenewable feedstocks, includ-
ing sugar beet, starch crops such as maize, wood, wheat, corn, and other plant
wastes through microbial strain and biological fermentation process. In a typical
process, extracted sugarcane juice with high sucrose content is anaerobically fer-
mented to produce ethanol. At the end of the fermentation process, ethanol is dis-
tilled in order to remove water, yielding an azeotropic mixture of ethanol + water
with a high content of the former. Ethanol is then fully dehydrated at high tem-
peratures over a solid catalyst to produce ethylene and, subsequently, polyethylene
(Guangwen et al. 2007) (Fig. 11.5).
Bio-based polyethylene has exactly the same chemical, physical, and mechani-
cal properties as petrochemical polyethylene. Braskem in Brazil is the largest pro-
ducer of bio-PE with 52 % market share, and this is the first certified bio-PE in
the world. Similarly, Braskem is developing other bio-based polymers such as bio-
polyvinyl chloride, bio-polypropylene, and their copolymers with similar indus-
trial technologies. The current Braskem bio-based PE grades are mainly targeted
towards food packing, cosmetics, personal care, automotive parts, and toys. Dow
Chemicals in the US in cooperation with Crystalsev is the second largest pro-
ducer of bio-PE with 12 % market share. Solvay in Belgium is another producer
of bio-PE; it has 10 % share in the current market. Solvay is also a leader in the
328 W. Brostow and T. Datashvili

Fig. 11.5  Process for green-PE production (http://www.sojitz.com/en/news/2012/07/20120705.php)

production of bio-PVC with similar industrial technologies. China Petrochemical

Corporation also plans to setup production facilities in China to produce bio-PE
from bioethanol (Haung et al. 2008).
Bio-PE can replace all the applications of current fossil-based PE. It is widely
used in engineering, agriculture, packaging, and many day-to-day commodity
applications because of its low price and good performance.
Starch 
Starch is a unique bio-based polymer because it occurs in nature as discrete gran-
ules. Starch is the end product of photosynthesis in plants—a natural carbohy-
drate-based polymer that is abundantly available in Nature from various sources
including wheat, rice, corn, and potato. Essentially, starch consists of the linear
polysaccharide amylose and the highly branched polysaccharide amylopectin. In
particular, thermoplastic starch is of growing interest for the industry. The thermal
and mechanical properties of starch can vary greatly and depend upon such factors
as the amount of plasticizer present. The Tg varies between −50 and 110 °C, while
the elastic modulus is similar to polyolefins (Jane 1995). Several challenges exist
in producing commercially viable starch plastics. Starch’s molecular structure is
complex and partly nonlinear, leading to issues with ductility. Starch and starch
thermoplastics suffer from the phenomenon of retrogradation—a natural increase
in crystallinity over time, leading to increased brittleness. Plasticizers need to be
found to create starch plastics with mechanical properties comparable to polyole-
fin-derived packaging. Plasticized starch blends and composites and/or chemical
modifications may overcome these issues, creating biodegradable polymers with
sufficient mechanical strength, flexibility, and water barrier properties for commer-
cial packaging and consumer products (Maurizio et al. 2005; Orozco et al. 2009;
Espindola-Gonzalez et al. 2011).
10  Environmental Impact of Natural Polymers 329

Novamont (an Italian company but with plants also in the US) is one of the
leading companies in processing starch-based products. The company produces
various types of starch-based products using proprietary blend formulations. There
are other companies around the world producing starch-based products in a similar
scale for various applications (Doug 2010).
Applications of thermoplastic starch polymers include films, such as for shop-
ping bags, fishing bait bags, overwraps, flushable sanitary products, packaging
materials, and special mulch films. Potential future applications could include
foam loose-fill packaging and injection-molded products such as ‘take-away’ food
containers. Starch and modified starches have a broad range of applications both in
the food and non-food sectors. In Europe in 2002, the total consumption of starch
and starch derivatives was approximately 7.9 million tons, of which 54 % was
used for food applications and 46 % in non-food applications (Frost and Sullivan
report 2009).
The largest users of starch in the European Union (30 %) are the paper,
cardboard, and corrugating industries (Frost and Sullivan report 2009). Other
important fields of starch application are textiles, cosmetics, pharmaceuticals, con-
struction industry, and paints. In the medium and long term, starch will play an
increasing role in the field of “renewable raw materials” for the production of bio-
degradable plastics, packaging material, and molded products.
Cellulose 
Cellulose is the predominant constituent in cell walls of all plants. Cellulose is a
complex polysaccharide with crystalline morphology. Cellulose differs from starch
where glucose units are linked by ß-1,4-glycosidic bonds, whereas the bonds in
starch are predominantly α-1,4 linkages. The most important raw material sources
for the production of cellulosic plastics are cotton fibers and wood (Brostow et al.
2009, 2010b). Plant fibers are dissolved in alkali and carbon disulfide to create vis-
cose, which is then reconverted to cellulose in cellophane form following a sulfu-
ric acid and sodium sulfate bath. There are currently two processes which are used
to separate cellulose from the other wood constituents (Fig. 11.6). These methods,
sulfite and pre-hydrolysis Kraft pulping, use high pressure and chemicals to sepa-
rate cellulose from lignin and hemicellulose, attaining greater than 97 % cellulose
purity. The main derivatives of cellulose for industrial purposes are cellulose ace-
tate, cellulose esters (molding, extrusion, and films), and regenerated cellulose for
fibers.
Cellulose is a hard polymer and has a high tensile strength of 62–500 MPa and
elongation of 4 % (Bisanda and Ansell 1992). In order to overcome the inherent
processing problems of cellulose, it is necessary to modify it, plasticize, and blend
with other polymers. The mechanical and thermal properties vary from blend to
blend depending on the composition. The Tg of cellulosic derivatives ranged
between 53 and 180 °C (Picker and Hoag 2002).
Eastman Chemical is a major producer of cellulosic polymers. FKuR launched
a biopolymer business in the year 2000 and has a capacity of 2800 metric ton/year
of various cellulosic compounds for different applications (Doug 2010).
330 W. Brostow and T. Datashvili

Fig. 11.6  Wood composition reproduced with permission from Royal Society of Chemistry

Licence number 3650080883796

There are three main groups of cellulosic polymers that are produced by chemi-
cal modifications of cellulose for various applications. Cellulose esters, namely
cellulose nitrate and cellulose acetate, are mainly developed for film and fiber
applications. Cellulose ethers, such as carboxymethyl cellulose and hydroxyethyl
cellulose, are widely used in construction, food, personal care, pharmaceuticals,
paint, and other pharmaceutical applications (Kamel et al. 2008). Finally, regen-
erated cellulose is the largest bio-based polymer produced globally for fiber and
film applications. Regenerated cellulose fibers are used in textiles, hygienic dis-
posables, and home furnishing fabrics because of its thermal stability and high
modulus (Kevin et al. 2001).
Chemically pure cellulose can be produced using a certain type of bacteria.
Bacterial cellulose is characterized by high purity and high strength. Currently,
applications for bacterial cellulose outside food and biomedical fields are rather
limited because of its high price. The other applications include acoustic dia-
phragms, mining, paints, oil gas recovery, and adhesives. However, the low yields
and high costs of bacterial cellulose represent barriers to large-scale industrial
applications (Prashant et al. 2009).
Chitin and Chitosan 
Chitin and chitosan are the most abundant natural amino polysaccharide and valua-
ble bio-based natural polymers derived from shells of prawns and crabs. Currently,
chitin and chitosan are produced commercially by chemical extraction process
from crab, shrimp, and prawn wastes (Roberts 1997). The chemical extraction of
chitin is quite an aggressive process based on demineralization by acid and depro-
teination by the action of alkali followed by deacetylated into chitosan (Roberts
1997). Chitin can also be produced by using enzyme hydrolysis or fermentation
10  Environmental Impact of Natural Polymers 331

process, but these processes are not economically feasible on an industrial scale
(Win and Stevens 2001). Currently, there are few industrial-scale plants of chitin
and chitosan worldwide located in the USA, Canada, Scandinavia, and Asia.
Chitosan displays interesting characteristics including biodegradability, bio-
compatibility, chemical inertness, high mechanical strength, good film-form-
ing properties, and low cost (Espindola-Gonzalez et al. 2011; Marguerite 2006;
Virginia et al. 2011; Liu et al. 2012). Chitosan is being used in a vast array of
widely varying products and applications—ranging from pharmaceutical and
cosmetic products to water treatment and plant protection. For each application,
different properties of chitosan are required—dependent on the degree of acetyla-
tion and molecular weight. Chitosan is compatible with many biologically active
components incorporated in cosmetic product composition. Due to its low toxicity,
biocompatibility, and bioactivity, chitosan has become a very attractive material in
such diverse applications as biomaterials in medical devices and as a pharmaceuti-
cal ingredient (Bae and Moo-Moo 2010). Chitosan has applications in shampoos,
rinses, and permanent hair-coloring agents. Chitosan and its derivatives also have
applications in the skin care industry. Chitosan can function as a moisturizer for
the skin, and because of its lower costs, it might compete with hyaluronic acid in
this application (Bansal et al. 2011).
Pullulan 
Pullulan is a linear water-soluble polysaccharide mainly consisting of maltotriose
units connected by α-1,6 glycosidic units. Pullulan was first reported by Bauer in
1938 and is obtained from the fermentation broth of Aureobasidium pullulans.
Pullulan is produced by a simple fermentation process using a number of feed-
stocks containing simple sugars (Bernier 1958). Pullulan can be chemically modi-
fied to produce a polymer that is either less soluble or even completely insoluble
in water. The unique properties of this polysaccharide are due to its characteristic
glycosidic linking. Pullulan is easily chemically modified to reduce the water solu-
bility or to develop pH sensitivity, by introducing functional reactive groups, etc.
Due to its high water solubility and low viscosity, Pullulan has numerous commer-
cial applications including use as a food additive, a flocculant, a blood plasma sub-
stitute, an adhesive, and a film (Zajic and LeDuy 1973). Pullulan can be formed
into molding articles which can resemble conventional polymers such as polysty-
rene in their transparency, strength, and toughness (Leathers 2003).
Pullulan is extensively used in the food industry. It is a slow-digesting mac-
romolecule which is tasteless as well as odorless, hence its application as a low-
calorie food additive providing bulk and texture. Pullulan possesses oxygen barrier
property (slow oxygen diffusion across a pullulan film) and good moisture reten-
tion; it also inhibits fungal growth. These properties make it an excellent material
for food preservation; hence, pullulan is used extensively in the food industry. In
recent years, pullulan has also been studied for biomedical applications in various
aspects, including targeted drug and gene delivery, tissue engineering, wound heal-
ing, and even in diagnostic imaging medium. Other emerging markets for pullulan
include oral care and formulations of capsules for dietary supplements and pharma-
ceuticals (Leathers 2003), leading to increased demand for this unique biopolymer.
332 W. Brostow and T. Datashvili

Collagen and Gelatin 

Collagen is a major insoluble fibrous protein in the extracellular matrix and in
connective tissue. In fact, it is the single most abundant protein in the animal king-
dom; all bones contain collagen. There are at least 27 types of collagens, and the
structures all serve the same purpose: to help tissues withstand stretching. The
most abundant sources of collagen are pig skin, bovine hide, and pork and cattle
bones. However, the industrial use of collagen is obtained from nonmammalian
species (Gomez-Guille et al. 2011) Gelatin is obtained through the hydrolysis of
collagen. The degree of conversion of collagen into gelatin depends on the pre-
treatment, function of temperature, pH, and extraction time (Johnston-Banks
1990).
Collagen is one of the most useful biomaterials due to its biocompatibility, bio-
degradability, and weak antigenicity (Maeda et al. 1999). The main application
of collagen films in ophthalmology is as drug delivery systems for slow release
of incorporated drugs (Rubin et al. 1973). It is also used for tissue engineering
including skin replacement, bone substitutes, and artificial blood vessels and
valves (Lee et al. 2001).
The classical food, photographic, cosmetic, and pharmaceutical applications of
gelatin is based mainly on its gel-forming properties. Recently in the food indus-
try, an increasing number of new applications have been found for gelatin in prod-
ucts in line with the growing trend to replace synthetic agents with more natural
ones (Gomez-Guille et al. 2011). These include emulsifiers, foaming agents, col-
loid stabilizers, biodegradable film-forming materials, and microencapsulating
agents.
Alginates 
Alginate is a linear polysaccharide that is abundant in nature as it is synthesized by
brown seaweeds and by soil bacteria (Draget et al. 1997). Sodium alginate is the
most commonly used alginate form in the industry since it is the first byproduct of
algal purification (Draget et al. 1997). Sodium alginate consists of α-l-guluronic
acid residues (G blocks) and ß-d-mannuronic acid residues (M blocks), as well as
segments of alternating guluronic and mannuronic acids.
Although alginates are a heterogeneous family of polymers with varying con-
tent of G and M blocks depending on the source of extraction, alginates with high
G content have far more industrial importance (Siddhesh and Edgar 2012). The
acid or alkali treatment processes used to make sodium alginate from brown sea-
weeds are relatively simple. The difficulties in processing arise mainly from the
separation of sodium alginate from slimy residues (Black and Woodward 1954). It
is estimated that the annual production of alginates is approximately 38,000 tons
worldwide (Helgerud et al. 2009).
Alginates have various industrial uses as viscosifiers, stabilizers, and gel-form-
ing, film-forming, or water-binding agents. These applications range from textile
printing and manufacturing of ceramics to production of welding rods and water
treatment (Teli and Chiplunkar 1986; Qin et al. 2007; Xie et al. 2001). The pol-
ymer is soluble in cold water and forms thermostable gels. These properties are
10  Environmental Impact of Natural Polymers 333

utilized in the food industry in products such as custard creams and restructured
food. Alginates are also used as stabilizers and thickeners in a variety of bever-
ages, ice creams, emulsions, and sauces (Iain et al. 2009).
Alginates are widely used as a gelling agent in pharmaceutical and food
applications. Studies into their positive effects on human health have broadened
recently with the recognition that they have a number of potentially beneficial
physiological effects in the gastrointestinal tract (Peter et al. 2011; Mandel et al.
2000). Alginate-containing wound dressings are commonly used, especially in
making hydrophilic gels over wounds which can produce comfortable, localized
hydrophilic environments in healing wounds (Onsoyen 1996). Alginates are used
in controlled drug delivery, where the rate of drug release depends on the type and
molecular weight of alginates used (Alexander et al. 2006). Additionally, dental
impressions made with alginates are easy to handle for both the dentist and the
patient as they fast set at room temperature and are cost-effective (Onsoyen 1996).
Recent studies show that alginates can be effective in treating obesity, and cur-
rently, various functional alginates are being evaluated in human clinical trials
(Georg et al. 2012).

10.4 Current Status and Future Trends

The use of bio-based feedstocks in the chemical sector is not a novel concept.
They have been industrially feasible on a large scale at least since the beginning
of the twenty-first century. However, the price of oil was so cost-effective, and the
development of oil-based products created so many opportunities that bio-based
products were not prioritized for a long time. Several factors, such as the limita-
tions and uncertainty in supplies of fossil fuels, environmental considerations, and
technological developments, accelerated the advancement of bio-based polymers
and products. It took more than a century to evolve the fossil fuel-based chemical
industry. However, the bio-based polymer industry is already catching up with fos-
sil fuel-based chemical industry, which has augmented since late 1990s. Thanks
to advancements in white biotechnology, the production of bio-based polymers
and other chemicals from renewable resources has become a reality. The first-
generation technologies mainly focused on food resources such as corn, starch,
rice, etc. to produce bio-based polymers. As the food-versus-fuel debate intensi-
fied, the focus of technologies changed to cellulose-based feedstocks - focusing on
waste from wood and paper, food industries, and even stems and leaves and solid
municipal waste streams. More and more of these technologies are already in the
pipeline to align with the above-mentioned waste streams; however, it may take a
few decades to develop the full spectrum of chemicals based on these technologies
(Michael et al. 2011).
Challenges that need to be addressed in the coming years include manage-
ment of raw materials, performance of bio-based materials, and their cost for pro-
duction. Economy of scale will be one of the main challenges for production of
334 W. Brostow and T. Datashvili

bio-based monomers and bio-based polymers from renewable sources. Building

large-scale plants can be difficult due to the lack of experience in new technolo-
gies and estimation of supply/demand balance. In order to make these technolo-
gies economically viable, it is very important to develop (1) logistics for biomass
feedstocks, (2) new manufacturing routes by replacing existing methods with high
yields, (3) new microbial strains/enzymes, and (4) efficient downstream process-
ing methods for recovery of bio-based products.
The current bio-based industry focus is mainly on making bio-versions of exist-
ing monomers and polymers. Performance of these products is well known, and it
is relatively easy to replace the existing product with similar performance of bio-
versions. Thus, all the polymers mentioned above often display similar properties
of current fossil-based polymers. However, many efforts are seen towards intro-
ducing new bio-based polymers with higher performance and value. For example,
Nature Works LLC has introduced new grades of PLA with improved thermal
and mechanical properties. New PLA-tri block copolymers have been reported to
behave like thermoplastic elastomer. Many developments are currently underway
to develop various polyamides, polyesters, polyhydroxyalkanates, etc. with a high
differentiation in their final properties for use in automotive, electronics, and bio-
medical applications.
The disadvantage of some of the new bio-based polymers is that they cannot be
processed in typical processing equipment. There is vast knowledge on additive-
based chemistry developed for improving the performance and processing of fos-
sil fuel-based polymers, and this knowledge can be used to develop new additive
chemistry to improve the performance and properties of bio-based polymers (Ray
and Bousmina 2005). For bio-based polymers like PLA and PHA, additives are
being developed to improve their performance, by blending with other polymers
or making new copolymers. However, the additive market for bio-based polymers
is still very small, which makes it difficult to justify major development efforts
according to some key additive supplier companies.
The use of nanoparticles as additives to enhance polymer performance has long
been established for petroleum-based polymers. Various nano-reinforcements cur-
rently being developed include carbon nanotubes, graphene, nanoclays, 2-D lay-
ered materials, and cellulose nanowhiskers. Combining these nanofillers with
bio-based polymers could enhance a large number of physical properties, includ-
ing barrier, flame resistance, thermal stability, solvent uptake, and rate of biodeg-
radability, relative to unmodified polymer resin. These improvements are generally
attained at low filler content, and this nano-reinforcement is an attractive route to
generate new functional biomaterials for various applications.
Even though new bio-based polymers are produced on an industrial scale, there
are still several factors which need to be determined for the long-term viability of
these polymers. It is expected that there will be feedstock competition—as global
demand for food and energy increases over time. Currently, renewable feedstocks
used for manufacturing bio-based monomers and polymers often compete with
requirements for food-based products. The expansion of first-generation bio-based
fuel production will place unsustainable demands on biomass resources and is
10  Environmental Impact of Natural Polymers 335

as much a threat to the sustainability of biochemical and biopolymer production

as it is to food production (Michael et al. 2011). Indeed, the European commis-
sion has altered its targets downwards for first-generation biofuels since October
2012, indicating its preference for non-food sources of sugar for biofuel produc-
tion (EurActiv.com 2012). Several initiatives are underway to use cellulose-based
feedstocks for the production of usable sugars for biofuels, biochemicals, and
biopolymers.
Overall, it is definitely possible for plastic production to meet the demands of
green chemistry for lean and clean production: solvent-free processes with effi-
cient use of resources, no byproduct formation, no waste, exploitation of renew-
able resources are in principle within our reach. Will we take advantage of the
possibility? As Abraham Maslow once said, “One’s only failure is failing to live
up to one’s own possibilities.” Let’s not fail!

References

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Chapter 11
Economic Impacts of Natural Polymers

Adeshola Raheem Kukoyi

11.1 Introduction

This chapter is a multidisciplinary discourse and exposition on the economic

impacts of natural polymers. The goal is to report, as much as possible, the cost–
benefit utility of natural polymers as a versatile natural resource with diverse
applications resulting from advances in science, technology, innovation, research
and development. This entails the value chain in their development, production,
distribution and consumption; involving people, intellectual and patent rights,
industry, investment and market for natural polymer-based goods and services.
Opportunities and challenges associated with natural polymer economy from raw
materials to finished products are being reported from the original works of differ-
ent authorities.
The perspectives employed in this chapter is a careful and objective attempt to
share knowledge on exactly how and why natural polymers may have economic
impacts and what constitutes it. Here, the author elucidates the concept, i.e. what
we mean by the term natural polymers with overview of the broader spectrum of
polymers, such as, synthetic and biodegradable polymers; biopolymers and bio-
materials. It considers the context, i.e. the sources, types, properties and poten-
tials of natural polymers. And presents the content, i.e. the applications or uses of,
demand and value of natural polymers to man.
The author relies on the arguments from reputable journals, books and reports
on natural polymers and the issues represented in this chapter are intended to pro-
mote a general understanding on what natural polymers are; their classification,

A.R. Kukoyi (*) 
University of Lagos, Akoka, Yaba, Lagos, Nigeria
e-mail: sungreeninternational@yahoo.co.uk; cosmogenemc@gmail.com

© Springer International Publishing Switzerland 2016 339

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_11
340 A.R. Kukoyi

relationship, sources, importance, demand, application, as well as the value they

add as food, medicine, healthcare or pharmaceuticals, cosmetics, textiles, packag-
ing and other industrial products, to national and global economy.
There are several natural polymers known to man. Natural polymers such as
collagen, elastin and fibrinogen make up much of the body’s native extracellular
matrix (ECM) (Bowlin et al. 2010). Protein, enzymes, muscle fibres, polysac-
charides and gummy exudates are the natural polymers being used effectively in
formulating the variety of pharmaceutical products. The well-known natural poly-
mers used in pharmacy and other fields are chitosan, carrageenan, ispaghula, aca-
cia, agar, gelatin, shellac, guar gum and gum karaya. These natural polymers are
widely used in pharmaceutical industry as emulsifying agent, adjuvant and adhe-
sive in packaging; and also well suited for pharmaceutical and cosmetic product
development (Shanmugam et al. 2005).
With the availability of variety of natural polymers, the manufacturers today
have achieved a great success in developing the most and promising therapeutic
systems, namely drug delivery systems, which provides an effective therapy to
the patients for prolonged periods (Shanmugam et al. 2005). Biodegradable poly-
mers are widely being studied as potential materials for site-specific drug delivery
because of its non-toxic, biocompatible nature. Natural polysaccharides have been
investigated for drug delivery applications as well as in biomedical fields. Modified
polymer has found its application as a support material for gene delivery, cell cul-
ture and tissue engineering (Jana et al. 2011). The structural similarity of some nat-
ural polymers with the components of the extracellular matrix (ECM) makes them
interesting candidates as biomaterials. The natural polymers with relevance in the
biomedical area can be divided into three major classes: polysaccharides (alginate,
hyaluronan, dextran, starch, cellulose derivatives, chitin derivatives), protein (colla-
gen, gelatin, fibrin, elastin, silk fibroin, soy protein) and bacterial polyesters (poly-
hydroxyalkanoates) (Azevedo et al. 2008).
Extracellular matrix (ECM) provides structure and mechanical integrity to tis-
sues, as well as communicating with the cellular components it supports to help
facilitate and regulate daily cellular processes and wound healing. An ideal tissue
engineering scaffold would not only replicate the structure of this ECM, but would
also replicate many functions that ECM performs (Bowlin et al. 2010).
A polymer is a large molecule (macromolecule) composed of repeating struc-
tural units. These subunits are typically connected by covalent chemical bonds.
Both synthetic and natural polymers are available but the use of natural polymers
for pharmaceutical applications is attractive because they are economical, readily
available and non-toxic. They are capable of chemical modifications, potentially
biodegradable and with few exceptions, also biocompatible (Kulkarni et al. 2012).
According to the Webster’s New World College Dictionary, Fourth Edition, a
polymer is a naturally occurring or synthetic substance consisting of giant mole-
cules formed from polymerization.1 Natural polymers or biopolymers are poly-
mers that occur naturally or are produced by living organisms (such as cellulose,

1http://www.yourdictionary.com/polymer.
11  Economic Impacts of Natural Polymers 341

silk, chitin, protein and DNA). By a wider definition, natural polymers can be
man-made out of raw materials that are found in nature.2 Natural polymers include
RNA and DNA that are so important in genes and life processes (Thomas 2013).
The DNA is transcribed to RNA and the trio of mRNA, tRNA and rRNA play very
crucial role in protein synthesis through the formation of polypeptides. Enzymes
are the protein-based catalyst that make metabolism possible inside living cells
and other polypeptides such as collagen and keratin make up the components of
skin, hair and nails. Natural rubber is a good example of natural polymer. Natural
polymers are the polymers derived from natural sources. Their effectiveness has
long been established, and they have been in use for decades. One such natural
polymer, chitosan, has been explored in every aspect of the medical field, e.g. drug
delivery, tissue engineering, gene delivery, etc. Further, alginates have been
reported to form gels, microparticles, nanoparticles, etc. To make natural polymers
more suitable for site-specific drug delivery, their properties have been tailored
(Galaev and Mattiasson 2008). Natural polymers constitute a wide class of impor-
tant polymers with many commercial applications, including food packaging,
fibres, fuel, coatings, automobile components, adhesives and genetic engineering
materials among others. The main categories of natural polymers are polysaccha-
rides (starch, chitin, chitosan, cellulose and their derivatives), proteins (amino
acids, enzymes and peptides) and polynucleotides (polyesters of phosphoric acid
and nucleosides). Others include rubber, lignin, humus, coal, kerogen, asphaltenes,
shellac and amber. With many diversified applications, natural polymers have
attracted a lot of research interests, particularly in biochemistry and material sci-
ence engineering (Pielichowski and Njuguna 2005).

11.2 Natural and Synthetic Polymers in the Industries

There are two types of polymers: synthetic and natural. Synthetic polymers are
derived from petroleum oil and made by scientists and engineers. Examples of syn-
thetic polymers include: nylon, polyethylene, polyester, Teflon and epoxy. Natural
polymers occur in nature and can be extracted. They are often water based. Examples
of naturally occurring polymers are silk, wool, DNA, cellulose and protein.3

11.2.1 Comparing Natural and Synthetic Rubber

Vulcanized rubber is a synthetic (man-made) polymer. Rubber can be found in

nature and harvested as latex (milky liquid) from several types of trees. Natural
rubber coming from tree latex is essentially a polymer made from isoprene units

2http://www.polymersolutions.com/blog/green-and-natural-polymers-on-the-rise.
3http://www.cmu.edu/gelfand/k12-teachers/polymers/natural-synthetic-polymers/index.html.
342 A.R. Kukoyi

with a small percentage of impurities in it. Rubber can also be made (synthesized)
by man. Synthetic rubber can be made from the polymerization of a variety of
monomers, including isoprene.
Natural rubber does not handle easily (it is sticky), nor does it have very good
properties or durability (it rots). It is usually vulcanized, a process by which the
rubber is heated in the presence of sulphur, to improve its resilience, elasticity and
durability. Synthetic rubber is preferable because different monomers can be
mixed in various proportions resulting in a wide range of physical, mechanical and
chemical properties. The monomers can be produced pure and addition of impuri-
ties or additives can be controlled by design to give optimal properties.4
Why Natural Polymers?
In developing countries, environmental pollution by synthetic polymers has
assumed dangerous proportions. Petroleum-derived plastics are not readily biode-
gradable and because of their resistance to microbial degradation, they accumulate
in the environment. In addition, in recent times, oil prices have increased mark-
edly. These facts have helped to stimulate interests in biodegradable polymers.
Biodegradable plastics and polymers were first introduced in the 1980s. Polymers
from renewable resources have attracted an increasing amount of attention over
the last two decades, predominantly due to two major reasons: first environmen-
tal concerns, and second the realization that our petroleum resources are finite.
There are many sources of biodegradable plastics, from synthetic to natural poly-
mers. Natural polymers are available in large quantities from renewable sources,
while synthetic polymers are produced from non-renewable petroleum resources.
Biodegradation of polymeric biomaterials involves cleavage of hydrolytically or
enzymatically sensitive bonds in the polymer leading to polymer erosion. A vast
number of biodegradable polymers have been synthesized recently and some
microorganisms and enzymes capable of degrading them have been identified
(Babak and Hadi 2013).

11.2.2 Some Natural Polymers of Economic Importance

The biodegradable polymers can be classified according to their chemical com-

position, origin and synthesis method, processing method, economic importance,
application, etc. In this reference, biodegradable polymers are classified according
to their origin into two groups: natural polymers which are obtained from natural
resources and synthetic polymers which are produced from oil. An overview of
these categories is given in Fig. 11.1, while Fig. 11.2 shows the world production
capacity of some biopolymers in 2010 (Imre and Pukanszky 2013).

4http://www.cmu.edu/gelfand/k12-teachers/polymers/natural-synthetic-polymers/index.html.
11  Economic Impacts of Natural Polymers 343

Fig. 11.1  Schematic presentation of bio-based polymers based on their origin and method of

production

Fig. 11.2  World production capacities of biopolymers as of 2010 (reproduced from Imre and

Pukanszky (2013) under creative commons license)
344 A.R. Kukoyi

11.2.3 Natural Biodegradable Polymers in the Industry

Biopolymers are polymers formed in nature during the growth cycles of all organ-
isms; hence, they are also referred to as natural polymers. Their synthesis gener-
ally involves enzyme-catalyzed, chain growth polymerization reactions of activated
monomers, which are typically formed within cells by complex metabolic processes
(Babak and Hadi 2013).

11.2.3.1 Biopolymers Directly Extracted from Biomass

Polysaccharides
For materials applications, the principal polysaccharides of interest are cellulose
and starch, but increasing attention is being given to the more complex carbo-
hydrate polymers produced by bacteria and fungi, especially to polysaccharides
such as xanthan, curdlan, pullulan and hyaluronic acid. These latter polymers gen-
erally contain more than one type of carbohydrate unit, and in many cases these
polymers have regularly arranged branched structures. Because of this difference,
enzymes that catalyze hydrolysis reactions during the biodegradation of each kind
of polysaccharides are different and are not interchangeable.
Thermoplastic starch
Starch is the major polysaccharide reserve material of photosynthetic tissues and
of many types of plant storage organs such as seeds and swollen stems. The prin-
cipal crops used for its production include potatoes, corn and rice. In all of these
plants, starch is produced in the form of granules, which vary in size and some-
what in composition from plant to plant (Chandra and Rustgi 1998). The starch
granule is essentially composed of two main polysaccharides, amylose and amylo-
pectin with some minor components such as lipids and proteins.
Cellulose and its derivatives
At present, cellulose is the most abundant polymer available worldwide with
an estimated annual natural production of 1.5 × 1012 tons and considered as an
almost inexhaustible source of raw materials. Figure 11.2 shows the world produc-
tion of biopolymers with cellulose-based biopolymers being 6 %.
Fibres (Lignocellulosic complex)
Plant fibres include bast (or stem of soft sclerenchyma) fibres, leaf or hard fibres,
seed, fruit, wood, cereal straw and other grass fibres. All these plant-based natural
fibres are lignocellulosic in nature and are composed of cellulose, hemicelluloses,
lignin, pectin and waxy substances. Lignocellulosic biomass comprises approxi-
mately 50 % of the global biomass and is by far the most abundant renewable
organic resource on earth. This woody material is comprised of 30–50 % cellulose,
20–50 % hemicellulose and 15– 35 % lignin, dependent upon the plant species and
environmental (growing) conditions.
11  Economic Impacts of Natural Polymers 345

Chitin and Chitosan

Chitin is a polysaccharide found in the shells of crabs, lobsters, shrimps and
insects or can be generated via fungal fermentation processes. Chitosan is the
deacylated derivative of chitin and forms the exoskeleton of arthropod.
Gums
Gums are a group of polysaccharides that can form gels in solution upon the intro-
duction of counterions. The degree of cross-linking is dependent on various factors
such as pH, type of counterion and the functional charge density of these polymers
(Chandra and Rustgi 1998).
Polypeptides (Proteins)
Proteins can be defined as natural polymers able to form amorphous three-dimen-
sional structures stabilized mainly by non-covalent interactions. The functional
properties of these materials are highly dependent on structural heterogeneity,
thermal sensitivity and hydrophilic behaviour of proteins. Numerous vegetable and
animal proteins are commonly used as biodegradable polymers.
Corn zein
Zein comprises a group of alcohol-soluble proteins (prolamins) found in corn
endosperm. It accounts for 50 % or more of total endosperm protein, and its only
known role is the storage of nitrogen for the germinating embryo (Gennadios
2002). It can be extracted with aqueous alcohol and dried to a granular powder.
Wheat gluten
Whereas dry wheat flour comprises 9–13 % protein and 75–80 % starch, wheat
gluten consists mainly of wheat storage protein (70–80 %, dry matter basis) with
traces of starch and non-starch polysaccharides (10–14 %), lipids (6–8 %) and
minerals (0.8–1.4 %). Osborne distinguished four wheat protein classes based
on their solubility in different solvents, namely, albumins, globulins, gliadins and
glutenins.
Soy protein
The major use of soybean in the food industry is as a source of oil, while soy pro-
tein concentrate and isolate are readily available as co-products of the oil process-
ing industry. Soy protein is a complex mixture of proteins with widely different
molecular properties. The major soybean proteins have molecular weights ranging
from 200 to 600 kDa.
Collagen and gelatin
Collagen is an abundant protein constituent of connective tissue in vertebrate
(about 50 % of total human protein) and invertebrate animals. Similar to cellulose
in plants, collagen molecules support mechanical stresses transferred to them by a
low-modulus matrix (Gennadios 2002).
346 A.R. Kukoyi

Casein and caseinates

Casein is the main protein of milk, representing 80 % of the total milk proteins.
It is a phosphoprotein that may be separate into various electrophoretic fractions,
αs1-casein, αs2-casein, β-casein and κ-casein, which differ in primary, secondary
and tertiary structure and molecular weight. These four different types of casein
are found in bovine milk in the approximate ratio of 4:1:4:1, respectively. Casein
exists in the form of micelles containing all four casein species complexed with
colloidal calcium phosphate. The casein micelles are stable to most common milk
processes such as heating, compacting and homogenization. Micellar integrity is
preserved by extensive electrostatic and hydrogen bonding, and hydrophobic inter-
actions (Gennadios 2002).
Whey proteins
Whey proteins are those proteins that remain in milk serum after pH/rennet coag-
ulation of casein during cheese or casein manufacture (Gennadios 2002). Whey
protein, which represents approximately 20 % of total milk proteins, is a mix-
ture of proteins with diverse functional properties. The five main proteins are
α-lactalbumins, β-lactoglobulins, bovine serum albumin, immunoglobulins and
preteose peptones.
Other proteins
There are other proteins, which have potential to use as biopolymeric materials for
different applications. Most important of them includes elastin (a major protein
component of vascular and lung tissue), egg albumins, fish myofibrillar protein
and wood keratin (Gennadios 2002).

11.2.3.2 Biopolymers Produced Directly by Natural or Genetically

Modified Organisms

Microbial polyesters
The microbial polyesters are produced by biosynthetic function of a microorgan-
ism and readily biodegraded by microorganisms and within the body of higher
animals, including humans. In the field of medicine, they can be used as implant-
ing material and a drug carrier.
Polyhydroxyalkanoates (PHAs)
Polyhydroxyalkanoates (PHAs) are a family of intracellular biopolymers synthe-
sized by many bacteria as intracellular carbon and energy storage granules.
Poly-3-hydroxybutyrate (PHB)
Among the PHA family, poly-3-hydroxybutyrate (PHB) is the most common
member; it belongs to the short chain length PHA with its monomers containing
4–5 carbon atoms.
11  Economic Impacts of Natural Polymers 347

Poly (Hydroxybutyrate-Hydroxyvalerate) (PHB/HV)

Blends of PHB family are usually compatible and co-crystallization is enhanced.
Poly-ε-Caprolactones (PCL)
Poly (ε-Caprolactone) (PCL) is aliphatic polyester and is of great interest as it can
be obtained by the ring opening polymerization of a relatively cheap monomeric
unit ‘ε-Caprolactone’. This polyester is highly processible as it is soluble in a wide
range of organic solvents (Nair and Laurencin 2007).
Bacterial Cellulose (BC)
Bacterial cellulose (BC) belongs to specific products of primary metabolism and
is mainly a protective coating, whereas plant cellulose (PC) plays a structural role.
Cellulose is synthesized by bacteria belonging to the genera Acetobacter, Rhizobium,
Agrobacterium and Sarcina. Its most efficient producers are Gram-negative, ­acetic
acid bacteria Acetobacter xylinum (reclassified as Gluconacetobacter xylinus),
which have been applied as model microorganisms for basic and applied studies on
cellulose.
Biopolymers (Polyesters) synthesized from bio-derived monomers
This category of biopolymers belongs to biodegradable polyesters and produced
by polycondensation or ring-opening polymerization of biologically derived
monomers.
Polylactic Acid or polylactide (PLA)
Among the family of biodegradable polyesters, polylactides (i.e. PLA) have been
the focus of much attention because they are produced from renewable resources
such as starch, they are biodegradable and compostable, and they have very low or
no toxicity and high mechanical performance, comparable to those of commercial
polymers.
Polyglycolic Acid (PGA)
Polyglycolide or Polyglycolic acid (PGA) is a biodegradable, thermoplastic poly-
mer and the simplest linear, aliphatic polyester. PGA has been known since 1954
as a tough fibre-forming polymer (Pachence et al. 2007) (Tables 11.1 and 11.2).

Table 11.1  List of common natural polymers (Thomas and John 2012)

Natural polymer Examples
Polysaccharides Starch, cellulose, chitin
Proteins Collagen/gelatin, casein, albumin, fibrinogen, silks
Polyesters Poly(hydroxyalkanoates)
Other polymers Lignin, lipids, shellac, natural rubber
348 A.R. Kukoyi

Table 11.2  List of important Fibre source Species Origin

natural fibres (Thomas and
Abaca Musa textilis Leaf
John 2012)
Agave Agave americana Leaf
Alfa Stippa tenacissima Grass
Bagasse – Grass
Bamboo (>1250 species) Grass
Banana Musa indica Leaf
Broom root Muhlenbergia macroura Root
Cantala Agave cantala Leaf
Caroa Neoglaziovia variegata Leaf
China jute Abutilon theophrasti Stem
Coir Cocos nucifera Fruit
Cotton Gossypium spp. Seed
Curaua Ananas erectifolius Leaf
Date palm Phoenix dactylifera Leaf
Flax Linum usitatissimum Stem
Hemp Cannabis sativa Stem
Henequen Agave fourcroydes Leaf
Isora Helicteres isora Stem
Istle Samuela carnerosana Leaf
Jute Corchorus capsularis Stem
Kapok Ceiba pentranda Fruit
Kenaf Hibiscus cannabinus Stem
Kudzu Pueraria thunbergiana Stem
Mauritius hemp Furcraea gigantea Leaf
Nettle Urtica dioica Stem
Oil palm Elaeis guineensis Fruit
Piassava Attalea funifera Leaf
Pineapple Ananas comosus Leaf
Phormium Phormium tenas Leaf
Roselle Hibiscus sabdariffa Stem
Ramie Boehmeria nivea Stem
Sansevieria Sansevieria Leaf
(bowstring hemp)
Sisal Agave sisalana Leaf
Sponge gourd Luffa cylindrica Fruit
Straw (cereal) – Stalk
Sun hemp Crorolaria juncea Stem
Cadillo/urena Urena lobata Stem
Wood (>10,000 species) Stem
11  Economic Impacts of Natural Polymers 349

11.2.4 Industrial and Economic Importance

of Natural Polymers

Depending on the starch source and processing conditions, a thermoplastic material

may be obtained with different properties suitable for various applications. Starch
has been widely used as a raw material in film production because of increasing
prices and decreasing availability of conventional film-forming resins (Chandra
and Rustgi 1998). Potential applications of starch films include production of dis-
posable food service ware, food packaging, purchase bag, composting bag and
loose fill products. Starch is also used in hygiene and cosmetics. Moreover, starch
has been used for many years as an additive to plastic for various purposes. Starch
was added as filler to various resin systems to make films that are impermeable to
water but permeable to water vapour.
Starch is also useful for making agricultural mulch films because it degrades
into harmless products when placed in contact with soil microorganisms. Starch
is also used in medical applications. For example, starch-based thermoplastic
hydrogels for use as bone cements or drug delivery carriers have been developed
through blending starch with cellulose acetate.
Important properties of thermoplastic starch-based materials include:
• compostable in accordance with DIN 54900
• high water vapour permeability
• good oxygen barrier
• not electrostatically chargeable
• low thermal stability
In general, the low resistance to water and the variations in mechanical proper-
ties under humid conditions affect the use of starch for various applications. As
water has a plasticizing power, the material behaviour changes according to the
relative humidity of the air. Strong hydrophilic character (water sensitivity) and
poor mechanical properties compared to conventional synthetic polymers are the
most important disadvantages of starch.
Cellulose has received more attention than any other polymer since it is
attacked by a wide variety of microorganisms. The biodegradation of cellulose
is complicated, because cellulose exits together with lignin; however, it is for-
tunate that pure cellulose does decompose readily (Chandra and Rustgi 1998).
Fermentation of cellulose has been suggested as a source of chemical such as etha-
nol and acetic acid, but this has not achieved any commercial importance to date.
The most significant cellulosic applications are in the paper, wood product, tex-
tile, film and fibre industries, but recently it has also attracted significant interest
as a source of biofuel product. The natural cellulosic carbon skeleton can be uti-
lized in two major applications on an industrial scale. The first is as regenerated
or mercerized cellulose (cellulose II, Rayon), which is not moldable and is used
only for film and fibre production. The second represents a broader class of appli-
cations, which employs chemically modified celluloses, principally the cellulose
esters (Chandra and Rustgi 1998).
350 A.R. Kukoyi

Lignocellulosic materials have the potential to be utilized as a feedstock for the

production of a wide variety of industrial and commodity products, ranging from
paper, lumber and platform chemicals to a variety of fuels and advanced materials,
including biodegradable polymers (Smith 2005). Plasticized blends of citrus pectin
and high amylase starch give strong, flexible films, which are thermally stable up
to 180 °C. Pectin is miscible with poly(vinyl alcohol) in all proportions. Potential
commercial uses for such films are water-soluble pouches for detergents and
insecticides, flushable liners and bags and medical delivery systems and devices.
Chitin is insoluble in its native form, but chitosan is water soluble. Chitosan
has been found to be non-toxic after oral administration in humans and is an FDA
approved food additive (Nair and Laurencin 2007). These biopolymers are bio-
compatible and have antimicrobial activities as well as the ability to absorb heavy
metal ions. They also find applications in the cosmetic industry because of their
water-retaining and moisturizing properties (Chandra and Rustgi 1998). Chitosan
has been formed into membranes and matrices suitable for several tissue engineer-
ing applications. Chitin derivatives can also be used as drug carriers. Chitosan was
used to develop injectable thermosensitive carrier material for biomedical appli-
cations. Due to the mild gelling conditions, the hydrogel has been found to be a
potential delivery vehicle for growth factors, small molecular weight drugs and
cells for localized therapy. The high chemical reactivity of chitosan has also led to
several chitosan–drug conjugates for cancer therapy. Chitosan gels, powders, films
and fibres have been formed and tested for many applications such as encapsula-
tion, membrane barriers, contact lens materials, cell culture and inhibitors of blood
coagulations (Pachence et al. 2007). Chitosan has good film-forming properties
and therefore can be used as a food packaging material.
A common type of gum is alginic acid which is present within the cell walls
and intracellular spaces of brown algae and has a structural role in giving flex-
ibility and strength to marine plants. Due to its non-toxicity, alginate has been
extensively used as a food additive and a thickener in salad dressings and ice
creams (Nair and Laurencin 2007). Alginate gels have been used widely in con-
trolled-release drug delivery systems. Alginates have been used to encapsulate
various herbicides, microorganisms and cells. Even though alginates have been
extensively investigated as biomaterials, one of the main disadvantages of using
alginate-based material is their inability to undergo enzymatic degradation by
mammals.
The film-forming properties of zein have been recognized for decades, and they
are the basis for its commercial utilization. Coating films are formed on hard sur-
faces by covering them with zein solutions and allowing the solvent to evaporate
off. The dried zein residues forms hard and glossy, scuff proof, protective coatings
that also are resistant to microbial attack. Zein coatings are used as oxygen, lipid
and moisture barriers for nuts, candies, confectionery products and other foods.
Rice fortified with vitamins and minerals has been coated with zein/stearic acid/
wood resin mixtures to prevent vitamin and mineral losses during washing in cold
water. Pharmaceutical tablets are zein-coated for controlled ingredient release
and protection (Gennadios 2002). Use of zein-based coatings has been suggested
11  Economic Impacts of Natural Polymers 351

for reducing oil uptake by deep fat fried foods, for protecting active ingredients
in chewing gum, for achieving controlled release of active ingredients in pharma-
ceutical tablets and for masking the taste of orally administered drugs (Gennadios
2002).
Wheat gluten is suitable for numerous food and non-food uses. Its main appli-
cation is in the bakery industry, where it is used to strengthen weak flours ren-
dering them suitable for bread baking (Gennadios 2002). The other potential
applications of gluten are very diverse: windows in envelopes, surface coatings
on paper, biodegradable plastic films for agricultural uses, water-soluble bags
with fertilizers, detergents, cosmetics, cigarette filters and additives and moulded
objects (Cuq et al. 1998). Wheat gluten-based materials are homogenous, transpar-
ent, mechanically strong and relatively water resistant. They are biodegradable and
a priori biocompatible, apart from some wheat gluten-specific characteristics such
as allergenicity.
Soy protein is an abundant and relatively cheap ingredient source for various
food applications. The functional properties that make soy protein useful in foods
include cohesiveness, adhesiveness, emulsification, dough and fibre formation,
whippability, solubility, and foaming (Gennadios 2002). Soy protein also is used
in infant formulas and in baked meat, and dairy products. The use of soy protein
as a film-forming agent can add value to soybeans by creating new channels for
marketing soy protein. Soy protein is a viable and renewable resource for produc-
ing edible and environmentally friendly biodegradable films. Soy protein films are
flexible, smooth, transparent and clear compared to other films from plant pro-
teins. These films have good mechanical properties but they are generally slightly
water resistant (Cuq et al. 1998). Soy protein films are typically prepared by dry-
ing thin layers of cast film-forming solutions (Gennadios 2002). Biodegradable
plastics were also produced from soy isolate and concentrate by a thermomolding
process.
The major sources of collagen currently used for industrial applications are
bovine or porcine skin or bovine or equine Achilles tendons (Pachence et al.
2007). Thermal or chemical dissociation of collagen polypeptide chains forms
product known as gelatin. The properties of collagen and gelatin are of great inter-
est to various fields, such as surgery (implantations; wound dressings), leather
chemistry (tanning), pharmacy (capsule production; tablet binding) and food sci-
ence (gels; edible films). Reportedly, about 65 % of gelatin manufactured world-
wide is used in foods, 20 % in photographic applications, 10 % in pharmaceutical
products and 5 % in other specialized and industrial applications. Collagen has
been extensively investigated for the localized delivery of low molecular weight
drugs including antibiotics. Collagen films have traditionally been used for prepar-
ing edible sausage casing. Gelatin has been successfully used to form films that
are transparent, flexible, water resistant and impermeable to oxygen. These films
were made by cooling and drying an aqueous film-forming solution based on gela-
tin. Gelatin is also used as a raw material for photographic films, and to microen-
capsulate aromas, vitamins and sweeteners.
352 A.R. Kukoyi

Its relative simple isolation and the useful properties of casein as an indus-
trial material and food ingredient have led to commercial production of casein
and caseinates since the nineteenth century. Casein and caseinates are suitable for
numerous food and non-food uses such as in industrial applications (especially
in glues, paper coatings, paints, leather finishing, textile fibres and plastics), and
in various food products. The end-users of casein and caseinates have gradually
shifted from industrial to food applications. About 70–80 % of the casein pro-
duced worldwide is used as a food ingredient (Gennadios 2002). Film-forming
properties of caseins have been used to improve the appearance of numerous
foods, to produce water-soluble bags and to produce origin or quality identifica-
tion labels inserted under pre-cut cheeses, to ensure the surface retention of addi-
tives on intermediate moisture foods and to encapsulate polyunsaturated lipids for
animal feeds (Cuq et al. 1998). Casein-based edible films are attractive for food
applications due to their high nutritional quality, excellent sensory properties and
potential to adequately protect food products from their surrounding environment.
The mechanical properties of casein and caseinate films, being neither too tough
nor too fragile, also make them suitable for edible purposes. Though more per-
meable to water vapour than plastic films, they are capable of retarding moisture
transfer to some degree. Casein and caseinate films dissolve nearly instantaneously
in water and this is desirable for many food applications.
Whey protein, a by-product of cheese industry, has excellent nutritional and
functional properties and the potential to be used for human food and animal feed.
The film-forming properties of whey proteins have been used to produce transpar-
ent, flexible, colourless and odourless films, such as those produced from caseins
(Cuq et al. 1998). The use of whey proteins to make edible packaging film mate-
rial brings several environmental advantages because of the film’s biodegradabil-
ity and its capacity to control moisture, carbon dioxide, oxygen, lipid, flavour and
aroma transfer. These properties offer the potential to extend the shelf life of many
food products, avoiding quality deterioration.
Other proteins have been also used for various purposes, including proteins
from rye, pea, barley, sorghum, rice, sunflower, pistachio and peanut (Gennadios
2002).

11.2.5 Demand for Natural Polymers in the United States

The United States is the world’s largest economy with a Gross Domestic Product,
GDP, of US $16.768 trillion5. According to a study on the market for natural pol-
ymers—Natural Polymers to 2016; US demand for natural polymers is forecast to
expand 6.9 % annually to US $4.6 billion in 2016. Cellulose ethers, led by methyl
cellulose, will remain the largest product segment. Exudate and vegetable gums

5http://www.data.worldbank.org/data-catalog/GDP-ranking-table.
11  Economic Impacts of Natural Polymers 353

will enjoy the most rapid gains in demand. The oilfield market will grow the fast-
est, driven by rising demand for guar gum in hydraulic fracturing fluids. This
study analyses the US $3.3 billion US natural polymer industry. It presents histori-
cal demand data for the years 2001, 2006 and 2011, and forecasts for 2016 and
2021 by market (e.g. food and beverages, medical, oilfield, cosmetics and toilet-
ries, paint and inks, construction, adhesives) and product (e.g. cellulose ethers,
starch and fermentation polymers, exudates and vegetable gums, protein-based
polymers, marine polymers). The study also considers market environment factors,
details industry structure, evaluates company market share and profiles 39 industry
players such as Ashland, Dow Chemical and CP Kelco US.6
Another report by Transparency Market Research which focused on the natu-
ral polymer market in the United States, estimates that in 2012, the demand for
natural polymers was US $4.95 billion, and will grow at a Compound Annual
Growth Rate, CAGR, of 6.2 % from 2012 to 2018, by which year it will stand at
US $7.12 billion. The report was titled: Natural Polymers—U.S. Industry Analysis,
Size, Share, Growth. The report finds that natural polymers are finding widespread
applications in the shipment of non-durable good, pharmaceuticals, as well as food
and beverages. As the shipments of all these products continue to show an upward
graph, the demand for natural polymers in the United States is slated to exhibit an
increase too. The study focuses on key applications such as food and beverages,
medical, oilfield, as well as other applications such as cosmetics, toiletries and
packaging classified under a segment called ‘others’.
An extensive analysis of all these segments reveals that in U.S. natural poly-
mers market, medical applications trumped all others, with a 25.6 % share of the
total revenue generated as of 2012. Also, the most extensively consumed type of
natural polymer in U.S. natural polymers market was cellulose ether; it constituted
36.5 % of all recorded consumption volumes as of 2012 Fig. 11.3.7
The demand for pharmaceuticals is increasing, and as a result, this application
area will also witness higher growth. This growth in pharma applications will have
a cascading effect wherein the demand for fermentation products and starch will
also spike. Cellulose ethers—derived from photosynthesis of wood pulp, cotton
and certain other plant types—are used in a variety of markets like medical, food
and beverages, and oilfield operations. Some of the most commonly used types of
cellulose ethers include: methyl cellulose (MC), carboxymethyl cellulose (CMC),
hydroxyethyl cellulose (HEC) and microcrystalline cellulose (MCC). According to
the estimates of the market study, by 2018, the demand for starch and fermentation
products will likely rise to 479.3 kilotons, exhibiting a CAGR of 12 % between
2012 and 2018.
The study also discusses the important end-user industries within the U.S.
natural polymers market. These end-user industries include: Adhesives and seal-
ant, ­toiletries, packaging, leather tanning, construction, paint and inks and textiles.

6http://www.freedoniagroup.com/Natural-Polymers.html.
7http://www.transparencymarketresearch.com/pressrelease/natural-polymers-market.htm.
354 A.R. Kukoyi

Fig. 11.3  U.S. Natural Polymer Market Volume Share, by Application in 2011 as reported by

transparency market research press release

One of the most important segments that generate considerable revenue for the
U.S. natural polymers market is that of packaging. A number of natural polymer-
based materials are required for packaging applications. In fact, several players in
the U.S. natural polymers market are focused mainly on the packaging segment
and conduct extensive research to come up with new and more innovative methods
for packaging.
This report also closely profiles the leading players in the U.S. natural poly-
mers market. Some of these names include: Ashland Inc., Economy Polymers
& Chemicals, Dow Chemical Company, JM Huber, Archer-Daniels-Midland,
Novamont, Plantic Technologies, FMC Corporation, Cargill Inc., Danisco,
Cereplast, CP Kelco, Allergan, Croda International Plc., BASF SE and AkzoNobel
NV (see Footnote 6).

11.2.6 Biomaterials Market in Brazil and Across the Globe

A biomaterial is a natural or synthetic material suited to replace or treat natural

body tissues and organs on interaction with biological systems. It traces its history
to more than 2000 years ago, when Romans, Chinese and Aztecs used gold for
dental applications. Biomaterials, which are compatible, have since been adapted,
improvised and technically enabled to improve body functions and replace dam-
aged tissues. They have evolved to include biodegradable materials that are easily
11  Economic Impacts of Natural Polymers 355

dissolved in the body. Advances in technology and the emergence of innovative

biomaterial products have enhanced their performance and applications.8
The Brazil market for biomaterials is expected to reach US $1.7 billion in 2015
from US $550.2 million in 2008 with a CAGR of 19.5 % from 2010 to 2015 (see
Footnote 8). Brazil, an emerging market, alongside, China, Russia and India;
belong to the group of ten (Pielichowski and Njuguna 2005) richest countries in
the world.9 In 2009, the orthopaedic biomaterial market recorded revenues of US
$236.5 million or 37.5 % of the total biomaterials products market. This is mainly
because of increasing application areas and introduction of sophisticated technolo-
gies in the biomaterials market. However, the orthopaedic biomaterial market is
estimated to grow at a CAGR of 17.2 % from 2010 to 2015. Cardiovascular bio-
material products market is the second highest market, contributing 36 % of the
total biomaterial products market. Ageing population (population above 60 years
was expected to reach 24 million by 2012), higher life expectancy and increase in
the incidence of ‘lifestyle and chronic diseases’ such as cardiovascular diseases
has influenced the growth of biomaterial products. According to the World Health
Organization, 32 % of the total mortality in Brazil was due to cardiovascular dis-
eases. Such a high incidence of diseases will increase the demand for cardiovascu-
lar biomaterial products such as cardiac stents.
The biomaterial products market in Brazil was expected to grow from US $690
million in 2010 to US $1.7 billion in 2015 at an estimated CAGR of 19.5 %. The
wound care biomaterial segment was expected to grow at a CAGR of 24.3 % from
2010 to 2015. Of all the application areas of biomaterial in Brazil, surgical appli-
ances and supplies account for the largest share; i.e. 39 % of the total applications
of biomaterial. With the technological advancements in orthopaedic and prosthetic
applications, there is an increase in demand for biomaterials in surgical appliances
and supplies.
The global biomaterial market is estimated to reach US $88.4 billion by 2017
from US $44.0 billion in 2012, growing at a CAGR of 15 %. Increased invest-
ments, funding and grants by government bodies worldwide, incessant rise in the
number of collaborations, conferences and research-related activities, technologi-
cal advancements, increasing applications of biomaterials and growing number of
elderly people are the major factors propelling the growth of the biomaterial mar-
ket globally. Immunological and inflammatory reactions, stringent regulatory sys-
tems, issue of fracture fatigue and wear and reimbursement concerns are the major
deterrents curbing the biomaterial market.
The global biomaterial market witnessed a plethora of growth opportunities.
Novel developments of biomaterial for wound healing, plastic surgery, tissue engi-
neering, ophthalmology, and neurology, colossal pool of cardiac patients in Asia,
rise of biomaterial market in China and Taiwan, and increased conferences and
research-related activities in the Rest of the World (RoW) countries are major

8http://www.marketsandmarkets.com/Market-Reports/biomaterials-393.html.
9http://www.marketsandmarkets.com/Market-Reports/biomaterials-392.html.
356 A.R. Kukoyi

factors influencing the growth of the biomaterial market. The burning issues
affecting the growth of biomaterial market are challenges to tissue engineering and
effect on suppliers by the Biomaterials Access Assurance Act.
The global biomaterial market is dominated by North America, followed by
Europe, Asia and Rest of the World (RoW). North America will continue to lead
the biomaterial market in the years to come, followed by Europe. North American
market growth is likely to be driven by increasing government investments in bio-
material sector, reimbursements offered by Centres for Medicare and Medicaid
Services (CMC) and rising ageing population who are the main consumers of bio-
materials. North American biomaterial market is expected to receive a significant
push due to phenomenal increase in new products such as botox, botulinum toxins
and hyaluronic-based injectibles.
The research report categorizes and analyses the global biomaterial market
under two broad segments—type and application. Both of these markets are bro-
ken down into segments and sub-segments, providing exhaustive value analysis
for the years 2010, 2011, 2012 and forecasts to 2017. Each market was compre-
hensively analysed at a granular level by geography (North America, Europe, Asia
and Rest of the World) to provide an in-depth information on the global scenario.
Under the global market segmentation by type, natural biomaterials mentioned
include: collagen and gelatin, cellulose, chitin, alginate and hyaluronic acid. The
biomaterial market, by type includes materials such as metals, polymers, ceram-
ics and natural biomaterials. Metals and polymers dominate the biomaterial mar-
ket. The polymers biomaterial market is expected to grow profusely in the coming
years; it is anticipated to grow at a CAGR of 22.1 % from 2012 to 2017.
Biomaterial is a combination of four major sciences, namely: basic science,
medical science, engineering science and forensic science. Biomaterials have been
in use for long in the human body to improve body functions and replace damaged
tissues. These biodegradable biomaterials have evolved from biomaterials that do
not react with the environment and easily dissolve in the body.10

11.2.7 Natural Polymers in Nanodrug Delivery

Natural polymers such as starch, chitosan and gelatin have found use in indus-
tries as diverse as food, textiles, cosmetics, plastics, adhesives, paper and pharma-
ceuticals. The food industry uses these polymers as thickening agents in snacks,
meat products, fruit juices. They are also used in the manufacture of disposable
items like fast food utensils and containers. From a pharmaceutical standpoint,
these polymers have been extensively used in solid oral dosage forms, where they
have been used as binders, diluents, disintegrants and matrixing agents. In recent
times, nanotechnology has started to make significant advances in biomedical

10http://www.marketsandmarkets.com/PressReleases/global-biomaterials-asp.
11  Economic Impacts of Natural Polymers 357

applications, including newer drug delivery techniques. There has therefore been
considerable research into developing biocompatible, biodegradable submicron
devices as drug delivery systems using natural polymers; this is because they
occur widely in nature, generally biocompatible, biodegradable, safe and non-
immunogenic. There are reports of these polymers been made into colloidal parti-
cles that act as carriers for both large and small drug molecules, conferring on the
drug molecules properties which enhance delivery actively or passively, thereby
tuning them for use as controlled, ocular, transdermal or intranasal delivery sys-
tems. In more advanced areas of drug delivery, these polymers have also been
tested for gene therapy and tissue engineering.
Although the initial properties of nanomaterial studied were for its physical,
mechanical, electrical, magnetic, chemical and biological applications, recent
attention has been geared towards its pharmaceutical application, especially in the
area of drug delivery. This is because of the challenges with the use of large-size
materials in drug delivery, some of which include poor bioavailability, in vivo sta-
bility, solubility, and intestinal absorption, sustained and targeted delivery to site of
action, therapeutic effectiveness, generalized side effects and plasma fluctuations
of drugs. Of recent, several publications in nanodrug delivery have been designed
to overcome these challenges due to the development and fabrication of nano-
structures. It has been reported that nanostructures have the ability to protect drugs
from degradation in the gastrointestinal tract; the technology also allows target
delivery of drugs to various areas of the body. The technology enables the deliv-
ery of drugs that are poorly water soluble and can provide means of bypassing the
liver, thereby preventing the first pass metabolism (Anwunobi and Emeje 2011).
Nanotechnology increases oral bioavailability of drugs due to their specialized
uptake mechanisms such as absorptive endocytosis and are able to remain in the
blood circulation for a longer time, releasing the incorporated drug in a controlled
fashion leading to less plasma fluctuations and minimizing side effects. It has
been reported that, due to the nano scale size of nanostructures, they are able to
penetrate tissues and are taken up by cells, allowing efficient delivery of drugs to
the target sites of action with the uptake of nanostructures observed to be 15–250
times greater than that of microparticles in the 1–10 µm range. Nanotechnology
improves their performance and acceptability by increasing effectiveness, safety,
patient adherence, as well as ultimately reducing healthcare costs. Nanotechnology
may also enhance the performance of drugs that are unable to pass clinical trial
phases. It definitely promises to serve as drug delivery carriers for the more chal-
lenging conventional drugs used for the treatment and management of chronic dis-
eases such as cancer, asthma, hypertension, HIV and diabetes. Despite the great
potentials of nanodrug delivery systems in revolutionizing patient treatment, its
safety in humans are of great concern (Anwunobi and Emeje 2011).
Many other synthetic/semi-synthetic polymers have been extensively utilized
and investigated as the preparation materials of microcapsules. Although the syn-
thetic polymers display chemical stability, their unsatisfactory biocompatibility still
limits their potential clinical applications. Because the natural polymers always
show low/non-toxicity, low immunogenicity and thereafter good biocompatibility,
358 A.R. Kukoyi

they have been the preferred polymers in drug delivery systems. Among the natural
polymers, alginate has become one of the most common materials used to form
microcapsules. Recently, scientists have turned their attention on tuning starch and
chitosan for use in nanodrug delivery. One of the ways to avoid the potential haz-
ards of nanodrug delivery may be by using natural polymers. This is because, apart
from occurring widely in nature, natural polymers are generally biocompatible,
biodegradable, non-immunogenic and safe (Anwunobi and Emeje 2011).
Natural polymers such as starch, gelatin and chitosan are no longer mere tra-
ditional excipients for use as binders, disintegrant or diluents, but are now being
applied widely as therapeutic drug carriers. The efficiency of delivery and release
of bioactive molecules from these systems is influenced by factors such as pol-
ymer type, drug loading, polymer breakdown, molecular weight, particle size,
interactions between the drug and polymer and several other technological and
pharmacotechnical factors. Natural polymers may not for now enjoy the robust-
ness of easy amenability to formulation design as compared to synthetic polymers,
but their excellent biocompatibility and safety makes them very important in the
preparation of various drug delivery systems with potential to achieve the formula-
tor’s desire for target or protected delivery of bioactive agents. However, increas-
ing works need to be done in the near future on these polymers. It is important
to note that apart from being safe, natural polymers are relatively very cheap. A
major limitation to the use of some of the natural polymers such as starch appears
to be its higher sensitivity to acid attack; however, modification has been proved to
impart acid resistance to the products. It is therefore important to optimize the pro-
cess of transition of these polymer granules from their native micro to the artificial
submicron level in greater detail and also pay greater attention to the toxicological
profiles of the nanoscale polymer derivatives. This is because, although generally
regarded as safe, derivatives of these natural polymers and in fact at submicron
levels may pose some safety challenges especially as carriers in drug delivery sys-
tems. The physicochemical properties of polymers depend largely on their botani-
cal or biological source, therefore, there is a greater need now than ever before for
scientists to begin to source for even cheaper polymers from our natural environ-
ment; plants, animals and microorganisms alike. If the pharmaceutical industries,
governments and donor agencies will take the risk of investing more in natural
product research in nanodrug delivery, then the answer to the current ‘safety pho-
bia’ by regulatory agencies may soon be at hand (Anwunobi and Emeje 2011).

11.2.8 Natural Polymers and the Economic Implications

of Capital and Technology Dependency on Less
Developed Countries

Advanced applications of natural polymers, including chitosan, alginate, starch, col-

lagen and gelatin, and their utilization in the fabrication of tissue engineering matri-
ces and drug delivery systems have been reported (Ivanova et al. 2014). Sales of
11  Economic Impacts of Natural Polymers 359

regenerative biomaterials have already exceeded US $240 million per annum, with
further growth being expected through the support of newly available and develop-
ing technologies, the existing regulatory guidelines and the commercial success of
the private sector within the aggregate field comprised of tissue engineering, regen-
erative medicine and stem cell therapeutics. In regenerative medicine, the genetic
engineering of proteins promises to overcome the limitations of traditionally used
autografts and allografts, by providing a platform for the on-demand expression of
biological components and highly controlled generation of new protein sequences
and self-assembling peptides with tunable properties.
Capital resources are rapidly growing and being dispersed to maximize the
returns of their owners throughout the world, so too is rapid technological change
(mostly in the West) profoundly affecting world trading relationships. One of the
most obvious examples of the impact of developed country technological change
on developing country export earnings is the development of synthetic substitutes
for many traditional primary products. Over the past five decades, synthetic substi-
tutes for such diverse commodities as rubber, wool, cotton, sisal, jute and skins—
sources of natural polymers, have been manufactured in increasing quantities. The
developing world’s market share of these natural products in all cases has fallen
steadily. For example, between 1950 and 1980, the share of the natural rubber in
total world rubber consumption fell from 62 to 28 %, and cotton’s share of total
fibre consumption dropped from 41 to 29 % (Todaro and Smith 2003).
Technological substitution, together with the low income and price elastic-
ity of demand for primary products and the rise of agricultural protection in the
markets of developed nations, goes a long way towards explaining why uncritical
adherence to the theoretical dictates of comparative advantage can be risky and
often unrewarding venture for many less developed countries, LDCs. On the other
hand, the worldwide availability of new technologies developed in the West has
provided many newly industrializing countries, NICs, the opportunity to capital-
ize on Western research and development expenditures. By first imitating products
developed abroad but not on the frontiers of technological research, certain LDCs
with sufficient human capital (e.g. the Asian NICs) can follow the product cycle
of international trade. Using their relatively lower wages, they move from low-
tech to high-tech production, filling manufacturing gaps left vacant by the more
industrialized nations. According to the dependency economists, the whole world
is divided between two sets of countries; DCs (developed countries) and LDCs
(less developed countries). The former are in the centre (Western Europe, Britain
and the United States) and the latter are in the periphery (backward countries of
Asia, Africa and Latin America). There are unequal centre–periphery relation-
ships whereby LDCs are dependent on DCs in trade, investment, technology, etc.
This dependence results in underdevelopment of the periphery because the cen-
tre is dominated by the powerful capitalist countries that exploit the former for
their benefit. The peripheral LDCs are heavily dependent on the centre for foreign
capital. Foreign capital leads to ‘external orientation’ of LDCs by exporting com-
modities, importing manufactures and making them dependent for industrializa-
tion of their economies. Sunkel posits that it is the stagnation of agriculture, high
360 A.R. Kukoyi

concentration of primary commodities for exports, high foreign exchange content

of industrialization and growing fiscal deficit in the peripheral countries which
necessitate foreign financing for them. The foreign investors exploit LDCs by
insisting on the choice of projects, making decisions on pricing, supply of equip-
ment, knowhow and personnel, etc. In fact, they impose a development pattern
that is not compatible with local needs. Further, the dependence on foreign capital
leads to a much higher outflow in the form of declared profits, royalties, transfer
pricing, payment of principal and interest to foreign investors of the centre.
The peripheral countries use excessively capital-intensive technologies
imported from the developed countries of the centre. These technologies are
inappropriate to the production and consumption needs of LDCs and are sold by
multinational corporations (MNCs) of developed countries. The technological
dependence of LDCs on DCs arises because of the urgency of importing technolo-
gies as they cannot innovate them. They lack information about the availability of
appropriate technologies which leads to exploitation of LDCs due to their weak
bargaining power. MNCs lead to economic and political distortions in LDCs.
Some of the economic distortions created by MNCs are transfer of technologies
to LDCs by restricting their right to use or change or transfer according to their
discretion or requirements. This leads to their total technological dependence on
MNCs. Capital-intensive technologies have limited labour absorption capacity
and thus add to unemployment in LDCs. They create social tensions by worsen-
ing the distribution of income. There are large wage differentials between workers
employed in the branches of MNCs and those engaged in local firms in LDCs.
Such wage differentials increase income inequalities and create social tensions
which retard the development of LDCs. Both Frank and Santos explain the tech-
nological development perpetrated by MNCs. The centre has spread its monopoly
to the peripheral countries through technological transfer. For this, LDCs have to
borrow from the centre. There is repatriation of profits, royalties, etc., by MNCs
to the centre. This worsens balance of payments (BOP) of LDCs. They resort to
devaluation and increase in money supply thereby leading to inflation with its
resultant adverse effects on the economy. Thus the peripheral countries are caught
in a web of dependence structure Jhingan (2005).

11.3 Conclusion

The economic impacts of natural polymers to national and global economy have
been discussed. Natural polymers have been used for ages to improve the qual-
ity of lives of people around the world. Traditionally, a lot of value has been cre-
ated or derived from the use of various kinds of fibres, especially cotton. Modern
improvements have resulted in better value for natural rubber. Natural polymers
are, undoubtedly, abundant, universal, diverse, renewable, biodegradable, biocom-
patible, non-toxic, safe, economical, versatile and indispensable sources of bioma-
terials. Natural polymers include a wide range of naturally occurring or derived
11  Economic Impacts of Natural Polymers 361

products classified as polysaccharides, proteins, polynucleotides and certain

­categories of polyesters. The natural polymer with the highest prevalence, demand
and perhaps application is cellulose; a polysaccharide used in a variety of industry.
The largest market for natural polymers, as reported, is the United States. Despite
the global trends in the development of natural polymers and the growing mar-
kets in Latin America, Europe and Asia; Africa is left behind. Substitutes to cotton
and natural rubber had dwindled natural polymers’ trade revenues for developing
countries over several decades and their competitive advantages in global produc-
tion reduced. Renewed interests in natural polymers are driven by environmental
pollution and degradation concerns over the use of non-biodegradable petroleum-
based substitutes, the rising cost of petroleum and the realization that petroleum
resources are finite and exhaustible. Investments in scientific, engineering and
technological research and development efforts by governments and other inter-
ests have yielded into various industrial applications for natural polymers. Natural
polymers development has impacted the scientific, engineering and technological
fields of agriculture, medicine, pharmaceuticals and packaging industry and the
economies of countries, mainly in the West; through a wide range of innovative
materials employed as food and beverages, healthcare and personal care products.
Manpower and technology advancements involving natural polymers have culmi-
nated in the novel gene and nanodrug delivery systems, as well as tissue engineer-
ing applications.
Although, the natural polymers market, globally, is worth billions of dollars;
developing countries, especially in Africa, have not benefitted much because of
intellectual, capital, technology, legal and trade constraints.

References

Anwunobi AP, Emeje MO (2011) Recent application of natural polymers in nanodrug delivery.
J Nanomedic Nanotechnol S 4:002. doi:10.4172/2157-7439
Azevedo HS, Santos TC, Reis RL (2008) Controlling the degradation of natural polymers for
biomedical applications. Natural-based polymers for biomedical applications, Cambridge,
Woodhead Publishing Limited
Babak G, Hadi A (2013) Biodegradable polymers. Licensee In Tech, Creative Commons
Attribution License
Bowlin et al (2010) The use of natural polymers in tissue engineering: a focus on electrospun
extracellular matrix analogues. Polymers, ISSN 2073-4360
Chandra R, Rustgi H (1998) Biodegradable polymers. Progress in Polymer Science
23:1273–1335
Cuq et al (1998) Proteins in agricultural polymers for packaging production, Cereal Chemistry
75(1):1–9
Galaev I, Mattiasson B (2008) Smart polymers: applications in biotechnology and biomedicine,
2nd edn. CRC Press, Boca Raton
Gennadios A (2002) Protein—based films and coatings. CRC Press LLC 134–149
Imre B, Pukanszky G (2013) Compatibilization in bio-based and biodegradable polymer blends.
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Ivanova EP, Bazaka K, Crawford RJ (2014) New functional biomaterials for medicine and
healthcare. Woodhead Publishing Limited, Cambridge
362 A.R. Kukoyi

Jana S, Gandhi A, Sen KK, Basu SK (2011) Natural polymers and their application in drug
­delivery and biomedical field. J PharmaSci Tech 1(1):16–27
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(P) Ltd, Delhi
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ISSN: 2229-3701
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Science 32:762–798
Pachence JM, Bohrer MP, Kohn J (2007) Biodegradable polymers. Principles of Tissue
Engineering, 3rd edn, Elsevier Inc, 323
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Shropshire, Rapra Technology Limited
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4(6):478–481
Thomas S, John MJ (2012) Natural polymers: an overview. Natural Polymers, vol 1: Composites,
Cambridge, Royal Society of Chemistry
Thomas S (2013) Natural polymers, biopolymers, biomaterials and their composites, blend and
IPNs, advances in material science, vol 2. Apple Academic Press Inc, Ontario
Todaro MP, Smith SC (2003) Economic development, 8th edn. Pearson Education Limited, Delhi
Trends and Forecast (2012–2018) Natural Polymers Market for Medical, Food and Beverage
and Oilfield Applications—US Industry Analysis, Size, Share, Growth. Transparency Market
Research, research and markets.com, June 2013
Chapter 12
Future Perspectives

Ololade Olatunji, Géraldine Savary, Michel Grisel,

Céline Picard and Atul Nayak

12.1 Trends and Perspectives of Natural Polymers

in Cosmetics Industry

Companies specialized in the raw materials furnishing for cosmetic companies

have been recently developing some natural polymer associations, with possi-
ble synergies and/or multifunctional benefits. Among the numerous examples,
SEPPIC launched a xanthan gum (XG)/acacia gum combination (trade name:
Solagum AX®), owing an optimum gums ratio; this system brings improved
emulsions stabilizing properties and can be used with cold process. SOLIANCE
recently developed a XG/guar gum combination (trade name: Syner-GX®) that
allows obtaining gels with good stability versus electrolyte and temperature, and
soft touch.
Many commercial examples exist, but due to economic competition only few
scientific studies, for physicochemical or sensory aspects, are available for such
polymer associations. Recently, Jamshidian et al. (2014) investigated the poten-
tial relationship between rheological values and filament stretching property of
XG and hydroxypropyl guar (HPG) in pure and mixed aqueous solutions and

O. Olatunji (*) 
Chemical Engineering Department, University of Lagos,
Akoka, Lagos, Nigeria
e-mail: lolakinola@gmail.com
G. Savary · M. Grisel · C. Picard 
URCOM, Université du Havre, EA 3221, FR CNRS 3038, 25,
rue Philippe Lebon CS 80540, 76058 Le Havre Cedex, France
A. Nayak 
Department of Chemical Engineering, Loughborough University,
Loughborough, Leicestershire, UK

© Springer International Publishing Switzerland 2016 363

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1_12
364 O. Olatunji et al.

Fig. 12.1  Viscosity plot of X/HP Guar mixed solutions as a function of xanthan percentage at

0.25 % total polymer concentration and corresponding stretching properties (Jamshidian et al.
2014 reproduced with permission from Elsevier, Licence number 3633661456878)

also in cosmetic emulsions. In pure solution, distinct rheological behaviors were

observed between XG and HPG. XG solutions showed higher stretchability values
than HPG for concentration below 1 % w/w and then filament stretching proper-
ties were close for both polymers at higher concentrations. In mixed solutions, a
pronounced synergistic effect was observed for XG/HPG solution at a 25/75 ratio
whatever the total concentration tested (below 0.5 % w/w). Noteworthy is the
influence of the synergy on the stretching properties since the interaction between
XG and HPG results in an enhancement of the maximum filament length as visible
in Fig. 12.1.
If considering emulsions, XG demonstrated the major role in viscosity and fila-
ment stretching increment. This could be related to interactions between XG and
other ingredients present in the emulsion. So more rheological and textural param-
eters should be investigated in order to understand how XG governs the behaviors
of the system and why no interaction was observed with HPG in emulsion.
As described earlier in Chap. 9, many natural polymer derivatives (so-called
“artificial polymers”) are currently used for cosmetic product elaboration; most
were initially issued from widely available polysaccharides such as cellulose, guar,
or starch, and many others are also currently available. Nowadays, in relationship
with the “multifunctional” tendency and research for new natural-based ingredi-
ents, some research projects focus on the modification of some well-developed
polysaccharides. As an example, Roy et al. (2014) recently proposed a method for
selective and efficient grafting of alkyl residues on xanthan molecules backbone. A
series of hydrophobically modified xanthan with tunable grafting density ranging
from 0 to 29 % was obtained by coupling reaction onto the carboxylic functions
of the biopolymer. The native semi-rigid helix conformation of xanthan was kept
intact thus permitting to get high viscosity enhancement related to the native poly-
mer combined with intermolecular associations through alkyl chains. Rheological
characterization unambiguously evidence dramatic enhancement of the low shear
viscosity as illustrated in Fig. 12.2, but without modifying the well-known shear
thinning behavior of the native biopolymer.
12  Future Perspectives 365

Fig. 12.2  Master curves of
the dynamic viscosity (η′)
as a function of ω*aT with
Tref = 20 °C at 2 g/L (Roy
et al. 2014)

This example shows promising suspending capability of such xanthan deriva-

tives, which is of primary importance when formulating complex mixtures with
long-term utilization as required for most cosmetic products.
Other many promising research projects for developing new natural polymeric
systems for cosmetic formulation are in course, in both academic and industrial
laboratories. Typical examples are extraction and utilization of compounds issued
from abundant non alimentary biomass (e.g., proteins) or macroalgae (e.g., poly-
saccharides), or microalgae and microorganism biotechnology for producing novel
polysaccharides or proteins. The future of cosmetic industry largely depends on
such innovations.

12.2 Future Challenges of Parenteral Devices

In Chap. 10 we discussed microneedles as minimal invasive parenteral devices

because the needles are fabricated to penetrate a known depth in skin layers
than a hypodermic needle. Natural polymers have the potential to support the
sustained release of drugs in the skin and can prove advantageous for the biode-
gradable class of microneedles. However, the challenge arises to strengthen the
microneedles with the result of all microneedles piercing the skin at a reproduc-
ible depth. Synthetic biodegradable polymer such as poly(dl-lactic-co-glycolic
acid) PLGA and poly(l-lactic acid) (PLLA) possess high mechanical strength
366 O. Olatunji et al.

(Ishaug et al. 1994; Leung et al. 2008). The possibility of enhancing the natu-
ral polymeric formulation with blended synthetic, polymeric fibers in providing
improved mechanical strength properties is one direct solution.

12.3 Natural Polymer Bases in Gums in Food Applications

Chewing gums is an example of application of polyisoprenes in food. In the ear-

lier years of their existence, chewing gums were produced from natural gums such
as chicle, in addition to gutta and other natural polymer-based materials. As the
requirements become more sophisticated and the interests in synthetic polymers
grew, more chewing gum producers began to focus on the application of synthetic
polymers such as polyethylene, poly vinyl acetate, styrene-butadiene copolymers,
and isobutylene-isoprene copolymers to produce chewing gums. In prior inven-
tion, a natural polymer-based chewing gum consisted of naturally occurring guay-
ule rubber in combination with hydrogenated vegetable oil and polyvinyl acetate
as plasticizers, emulsifying agents, solvent, and inorganic filler (Glass et al. 1983).
However, today a large majority of the chewing gum in the commercial market
make use of synthetic polymers.
Although synthetic polymers are preferred for the consistency and desired
properties achievable, chewing gums based on synthetic polymers are gener-
ally hydrophobic causing them to stick to surfaces (Farber et al. 2010). Natural
polymers have more hydrophilic options such that non-stick chewing gums using
natural bases such as natural rubber could result in non-stick chewing gums.
Furthermore, natural polymer-based chewing gums are likely to result in more
ingestible chewing gums reducing the health hazards posed by intentional or unin-
tentional swallowing of chewing gums.
Part of the drawbacks from using natural-based polymers such as polyisoprene
for food application is the presence of the trans and cis isomeric forms and the
protein residues which could result in allergic reactions. Further developments in
processing techniques which can better eliminate these allergens from natural pol-
ymers will consequently result in more use food productions.

12.4 Nondestructive Testing

Acoustic emissions have recently been employed for nondestructive mechanical

characterization. In particular, this method has been applied to natural lignocel-
lulose-based fibers such as jute and flax. Such nondestructive testing could play
an important role in cases where in vivo testing of natural polymer-based com-
posites applied in for example food, tissue engineering to test the real-time integ-
rity of a scaffold, or in food to test the mechanical properties of an edible natural
polymer-based food packaging after production without destroying the product.
12  Future Perspectives 367

Nondestructive mechanical testing is also important where the natural polymer-

based material or the fabrication process is rather expensive (for example hyaluro-
nan sourced from humans).

12.5 Addressing Limitations of Natural Polymers Due

to Thermomechanical Sensitivity

In processes such as thermal spraying which has been effectively used in the
polymer industry for processing of filaments (Rawal and Mukhopadhyay 2014),
natural polymers are not commonly applied due to their thermal sensitivity and
processibility. This technique generally involves melting and accelerating micro-
particles toward a substrate unto which they solidify and adhere to form thin layer.
Thermal spraying is of different forms, and the melting could be through either a
combustion or plasma flame.
The limitation of such methods in natural polymer is due to the weak thermo-
plasticity of natural polymers compared to synthetic polymers. Such limitations
can be addressed either by adapting the processing techniques to suit the thermal
tolerance of natural polymers or alternatively or in addition, new blends can be
developed with various natural polymers such as their combined effect results in a
fully natural polymer-based blend with desirable thermomechanical properties for
thermal processing.

References

Farber TCA et al (2010) Safety assesment for a novel ingredient for removable chewing gum.
Food Chem Technol 48:831–838
Glass M, Koch E, Corsello V (1983) Chewing gum base. US, Patent No. US4415593A
Ishaug SL,Yaszemski MJ, Bizios R, Mikos AG (1994) Osteoblast function on synthetic biode-
gradable polymers. J Biomed Mater Res 28:1445–145
Jamshidian M, Savary G, Grisel M, Picard C (2014) Stretching properties of xanthan and
hydroxypropyl guar in aqueous solutions and in cosmetic emulsions. Carbohydr Polym
112:334–341
Leung L, Chan C, Baek S, Naguib H (2008) Comparison of morphology and mechanical proper-
ties of PLGA bioscaffolds. Biomed Mater 3:1–9
Rawal A, Mukhopadhyay S (2014) Melt spinning of synthetic polymeric filaments. In: Advances
in filament yarn spinning of Textiles and Polymers, pp 75–99
Roy A, Comesse S, Grisel M, Hucher N, Souguir Z, Renou F (2014) Hydrophobically modified
xanthan: an amphiphilic but not associative polymer. Biomacromolecules, 15(4):1160–1170
Index

A E
Alginate, 332, 333 Electrospinning, 38, 48, 56
Emulsions, 116, 117, 123, 125, 126, 128–130,
137–139, 145–148, 152, 220, 231–234,
B 236, 238, 241, 242, 244, 247, 253
Biodegradable, 104, 163–167, 169, 170, 173, Extracellular matrix, 340
175, 177, 179 Extrusion, 164, 174, 176
Biodegradable polymers, 339, 340, 342, 344,
345, 350
Biomaterials, 339, 340, 342, 350, 354–356, F
359, 360 Fiber, 20, 21, 23, 24, 26–29, 38, 40, 47, 51, 52
Biopolymers, 315, 316, 319, 322, 335, 339, Filtration, 187, 188, 193, 198, 201
340, 342, 344, 346, 347, 350 Flocculation, 125, 126, 129, 146
Blends, 20, 21, 24, 25, 29, 32, 36, 39, 56 Fluid, 185, 187, 189, 190, 192, 212
Food, 163–165, 168, 171, 173–175, 177, 179
Formulations, 221, 226, 228, 231, 232, 234,
C 237, 244, 248, 250
Cellulose starch, 227, 271
Chitin, 2, 7
G
Chitosan, 63, 70–74, 88, 265, 267, 268, 275,
Gas, 186, 201, 212
279, 280, 286, 287, 289, 291, 293,
Gelatin, 64–69, 88, 268, 269, 296, 297, 299
296, 299
Gels, 116, 123, 134–137, 139
Circulation, 186, 191–193, 198, 201, 212
Gluten, 164, 169, 170
Composites, 20–22, 24–26, 28, 29, 36, 48,
Green-PE, 327
51, 56
Gums, 222, 226, 227, 231, 252, 254
Cosmetics, 219, 221, 226, 232, 238, 239,
242, 245, 249, 257
H
Healing, 96, 102, 104, 106, 110
D Hyaluronic acid, 222, 227, 248, 249
Drilling, 185–191, 193, 201, 212 Hydrogel, 95, 96, 98, 102, 103, 264, 267,
Drug delivery, 264–268, 271, 273–275, 277, 286–288, 290, 292, 293, 296, 297,
279, 281, 283, 285, 286, 288, 291, 293, 299, 301
296, 301 Hydrolysis, 64, 65, 67, 74, 76, 84, 87

© Springer International Publishing Switzerland 2016 369

O. Olatunji (ed.), Natural Polymers, DOI 10.1007/978-3-319-26414-1
370 Index

L Polylactic acid, 321, 322

Leaching, 99, 110 Polymer, 1, 2, 8, 9, 14, 185, 187, 190, 191,
194, 200, 205, 206, 208–212
Polymer matrix, 21, 26, 27, 32, 51
M Polysaccharides, 115, 116, 123, 124, 126,
Market, 316, 319, 322, 327, 331, 334 130, 135, 137, 140, 142, 144, 148,
Matrix, 94, 98, 101, 108 226, 227, 231, 234, 235, 239, 242,
Microneedles, 272, 284, 300 244, 247–249, 257
Microstructure, 117, 138 Protein, 1, 3, 8, 9, 11, 13, 115, 116, 123,
Modified starch, 79 124, 126, 129, 130, 135–138, 142,
Moulding, 164 143, 146, 147, 152, 153, 222, 226,
Mud, 186–190, 192 234, 239, 244, 249, 257
Proteins polysaccharides, 1, 42, 116, 226, 257
Pullulan, 331, 344
N
Nanocellulose, 29, 32, 35, 36, 47, 48, 55
Natural polymers, 339, 340 R
application of, 115 Renewable, 317–319, 321, 322, 326, 329, 334
biomedical application of, 93 Rheology, 221, 226, 228, 231, 234, 235, 238,
classification of, 1 242
cosmetics, 219
economic impacts of, 339
environmental impact of, 315 S
extraction of, 63 SEM, 37, 38, 51, 52
future perspectives, 363 Scaffolds, 93–96, 98–103, 110
in engineering, 185 Stability, 219, 234–238, 241, 250, 252, 254,
in food, 115 257
modification of, 63 Stabilizers, 117, 123, 126, 131, 150, 153
on packaging industry Starch, 63, 79, 81–83
challenges, 163 Supersaturated CO2
current application, 163
personal care products, 219
pharmaceutical applications of, 262 T
processing and characterization of, 19 Thickeners, 117, 129, 131, 132, 134
purification of, 63

V
O Viscosity, 187, 189, 191, 193
Oil, 185, 187, 188, 191, 201, 203, 204, 212

W
P Wound, 96, 104, 106, 110
Pectin, 2, 6
Pharmaceuticals, 164, 171, 178
Polyhydroxyalkanoate, 324 X
Polyisoprene, 1, 14, 15 XRD, 44, 46, 56