A PROJECT REPORT

ON

POLY LACTIC ACID

Submitted in the partial fulfilment

Post Graduate Diploma in Packaging (Semester-I)

(2023 – 2025)

Submitted by: BHASKAR BHATT

(PG/M/23/010)

Under the guidance of

Dr. Babu Rao Duduri,

Training & Education Department

Indian Institute of Packaging- Mumbai

Submitted To Indian Institute of Packaging E-2,

MIDC, Area, Andheri East, Mumbai – 400 093.

 CERTIFICATE

This is to certify that Bhaskar Bhatt student of 39th batch (2023-2025), was submitted project entitle

on “POLY LACTIC ACID” for the award of post graduate diploma in packaging (PGDP) for semester

1, under my supervision. To the best of my knowledge, the matter embodied in the report has not been

submitted previously in this institute.

 INDEX

SR NO. CONTENT PAGE NUMBER

1 INTRODUCTION 6
2 MANUFACTURING 7
2.1 RING OPENING POLYMERIZATION 8
2.2 DIRECT POLYCONDENSATION 9
2.3 FILM FORMATION 10
3 PROPERTIES OF PLA FILM 12
3.1 SEALING PROPERTIES 12
3.2 BARRIER PROPERTIES 13
3.3 MECHANICAL PROPERTIES 14
3.4 CRYSTALLINITY 15
3.5 MOLECULAR WEIGHT 15
3.6 GLASS TRANSITION TEMPERATURE 15
4 BLENDS AND COPOLYMERIZATION 16
5 APPLICATIONS IN PACKAGING 20
6 TOP MANUFACTURERS OF PLA 22
7 CONCLUSION 25
8 REFERENCES 26

LIST OF FIGURES
Figure-1: Manufacturing process of PLA resins
Figure-2: PLA D/L isomer configurations
Figure-3: Isomer configurations of cyclic Lactide units
Figure-4: Schematic representation of blown film extrusion
Figure-5: Cast Film Extruder

Figure-6: Mechanisms behind the heat sealing of flexible packages

Figure-7: PLA PEG copolymer

Figure 8: PLA Chitosan copolymer

Figure-9: PLA Enantiomers and racemic mixture

Figure-10: Food wrapped in PLA film

Figure-11: Packaging application of PLA film
Figure-12: Major Manufacturers of PLA film
Figure-13: TDS screenshot of Natureworks Ingenio
 ACKNOWLEDGEMENT
THIS PROJECT HAS BEEN SUPPORTED BY MANY PEOPLE WHOSE ADVICE AND ENCOURAGEMENT
WERE CRITICAL AND I AM INDEBTED TO ALL OF THEM. I EXPRESS MY DEEP SENSE OF GRATITUDE TO
JOINT DIRECTOR Dr. BABU RAO GUDURI FOR HIS VALUABLE CONTRIBUTION, ADVICE, GUIDANCE
AND TREMENDOUS ENCOURAGEMENT WITHOUT WHICH THIS PROJECT WOULD NOT HAVE BEEN
COMPLETED. MY HEARTFELT SUPPORT ALSO GOES FOR THE COMMENDABLE COOPERATION
PROVIDED TO ME BY MY FAMILY WHO HAS BEEN A GREAT SOURCE OF INSPIRATION.

SIGNATURE OF HOD
ABSTRACT

Poly Lactic Acid films as a packaging material are bio degradable and easily compostable.
Further their good processability, high crystallinity and hydrophobic nature make them potent
to be used as packaging material. Hence, they possess high arsenal of characteristics to
challenge presently prevalent non-bio degradable synthetic polymers. Albeit the positive
features, cost effectiveness of PLA films has been a hindering block, but with technological
advancements and simultaneous increase in prices of crude oil derived poly films,
economically they are catching up. Therefore PLA, a synthetic biopolymer, is set to be one of
the most used materials in packaging sector.

Poly (lactic acid) (PLA) is a non-toxic, compostable bio based material derived from starch
and/or sugar and has high mechanical strength and plasticity. It is accepted as GRAS
(Generally Recognized as Safe) by the Food and Drug Administration (FDA) and suitable for
using in food and beverage packaging. PLA is primarily obtained from lactic acid which can
be produced from renewable substances such as potato, wheat and corn starch. Petroleum
based polymers cause an increase in fuel energy utilization and greenhouse gas emissions,
however PLA is environmental friendly. Various polymers (protein, polycaprolactone (PCL)
and polyhydroxy butrate (PHB)), fillers (wood, flax, and ramie) and additives have been
combining with PLA in order to develop the performance of film and reduce the cost. On the
other hand, PLA plays an important role in nanotechnology applications. Nan fillers like clay,
montmorillonite and silica can be used for fortifying PLA composites. As a packaging
material, PLA has a potential for manufacturing flexible films, extruded packages, containers
of yoghurt, bottled water and juices, cups and lunch boxes. Moreover, in antimicrobial
packaging, PLA is an excellent material which is able to be successfully incorporated with
plant extracts (e.g. lemon), essential oils (e.g. oregano oil), enzymes (e.g. lysozyme) and
metals (e.g. silver) in order to develop antimicrobial characteristics. In this mini review, the
significance of PLA based packaging systems in food applications is discussed.

Keywords: Lactic Acid, Biodegradable Synthetic Polymer, Packaging Applications, Ring

Opening Polymerisation.
1. Introduction
Industrialisation and Urbanisations worldwide has led to a major change in how goods are
represented and sold in market. “Packaging and labelling” of goods has been the focal pointof
brand identity development in this dynamic market. While tertiary packings have been done
using paper board/wood, inner packaging, specially FMCG products, has been done extensively
with the use of non-biodegradable synthetic films such as polyethylene, polyethylene
terephthalate, polypropylene, polyvinyl chloride etc.

Recently the rise of green chemistry, due to increasing pollution levels and depleting crude oil
reservoirs, has shed light on the need of finding alternative substance that are less harmfulto the
environment and have all the desired properties of packaging materials.
Biodegradability of polymers and their life cycle assessments have been done by various
researchers across the world. Polyolefin films are destined to end at landfill sites. This along
with lack of awareness about their recycling poses a huge threat. Biopolymer films are
therefore the material that need to be modified to be usable as packaging films.

One of the prominent biopolymer films that has been researched and industrialised is Poly
Lactic Acid. Monomer units of Lactic acid are polymerised using either ring opening
mechanism or direct polycondensation. Polymer resins formed are then extruded and
blown/cast into PLA films. PLA films have high transparency and good processability. Their
high crystallization though makes them rigid. Hence certain plasticizers are added as and when
required during their manufacturing to meet the desired properties. Further the specialtyfilms
are compostable and are also recognized as safe component by food quality checking
authorities enabling them to be used in packaging of food materials.

One of key points that affects PLA film properties is the stereoisomerism of mono lactic acid
units. Lactic acid, a multiple OH group structure has chiral carbon with groups COOH, OH,
CH3 and H. This chirality allows two configurations of monomer i.e., L-Lactic acid and D-
Lactic Acid. Depending on monomer used, property of final PLA films relies.

Commercially produced films are being used in agricultural purposes as compostable bags and
trash liners. Multiple grades of PLA having different compositions and characteristics are
produced. Further development in this regard is required so that it could be used on further
large scale and replace current packaging materials. Cost and controlled degradation of blended
grades are desired with sufficient barrier and mechanical properties.
2. Manufacturing
Conventionally produced by ring opening polymerization, new techniques involving direct
polycondensation have been researched off late to make them economically more viable.

Lactic acid degradation does not allow easy polymerization into long chain poly lactic acid
molecules. Further D/L configuration affects their properties as well. Hence maintaining the
process parameters during PLA synthesis is very important. Direct polycondensation and ring
opening polymerization are the methods used to synthesize PLA from lactic acid.

Direct polycondensation of lactic acid involves dehydrating lactic acid and condensing them
low molecular weight poly lactic acid. This is further improvised by using chelating agents
and other sizing additives to increase molecular weight and hence the tensile strength of PLA
film.

Ring opening polymerization is more widely used method to synthesize PLLA/PDLA as it

gives more control as compared to direct polycondensation. This method involves formation
of lactide molecules and using catalyst and initiators to open lactide ring and support long
chain formations of lactic acid. Lactic acid monomers form a chain upon dehydration at
around 150°C to give oligomers of lactic acid. Further increasing the temperature and
reducing pressure leads to formation of lactide ring crystals. These lactide rings when opened
using Zinc and Tin based catalyst, give long chain poly Lactic acid macromolecules. Isotactic
D/L lactic acid chains tend to have crystalline pla films with well-defined structure. Meso
configuration of random D and L units of Lactic acid in PLA have amorphous nature which
gives a range of melting point and elasticity to PLA films.

Figure 1: Manufacturing

process of PLA resins

 Figure 2: PLA D/L isomer
configurations

2.1. Ring Opening Polymerization

The ring-opening polymerization of lactide is one of the methods for industrial production
of high-molecular-weight PLA. Lactide has three stereo configurations—l-lactide,
mesolactide, and d-lactide—as shown in Figure 3. As a cyclic dimer, it can be formed by
solvent-free dehydration under mild conditions. Commercially feasible methods for
obtaining and purifying lactide involve steps such as condensing lactic acid at 115–179 ◦C,
removing the condensed water, and removing the Molecules 2020, 25, 5023 5 of 18
mesolactic acid and low-molecular polymer through recrystallization to obtain pure l- or d,
l-lactide with high molecular weight. The industrial production method of lactide is the
same as the scheme mentioned above, but in different reactors, producing low-molecular-
weight prepolymers, and the final purification method is different. For example, Cargill
Inc. uses a reduced pressure–reflux method to remove residual water, lactic acid,
oligomers, and partial lactide. Nemphos changed the purification step, using a multistage
melt recrystallizer to remove LA and low-molecular polymer. Bhatia and colleagues used
inert gas to remove, recrystallize, and purify lactide. Other methods include the use of
lactide to gas-phase recrystallization to increase yield and weakly alkaline water/solvent
systems to extract lactide. In the method described above, after removing impurities, high-
purity lactide is generally obtained. After obtaining high-purity lactide, depending on the
catalyst, the ring-opening polymerization of lactide can adopt one of three mechanisms:
cation, anion, and coordination/insertion. Cationic initiators can generally be divided into
protic acid, Lewis acid, and alkylating or acylating reagents. Kricheldorf and his
colleagues found that triflic acid and methyl triflate, among many cationic initiators, could
effectively induce the polymerization of lactide. The choice of different anion inducers
causes deprotonation, resulting in inconsistent polymerization and racemization, leading to
polymers with different molecular weights. Considering that metal ions can cause toxicity
problems, it is not recommended to use butyl lithium or crown ether initiators. The use of
primary alkoxides, 6-valerolactone, or polyethylene glycol can produce clearly defined
polymers. The two above
methods have high reactivity,
and are usually prone to

Figure 3: Isomer configurations of

cyclic Lactide units
racemization and transesterification during the solvent reaction process, resulting in
impurities. The use of metal carboxylates, oxides, and alkoxides with lower activity to
produce polylactide with low toxicity and few impurities has been extensively studied in
commercial production applications. Studies found that the use of tin (II) and zinc
produces fewer impurities during the synthesis of high-molecular-weight polylactic acid,
resulting in the purest polylactic acid. For example, tin (II) di-2-ethyl hexanoic acid has
high catalytic activity and low toxicity. It was approved by the FDA, and it is a highly
suitable inducer. In addition to tin compounds, aluminum alkoxides and rare-earth
compounds are other catalyst systems that proceed through coordination/insertion
mechanisms. Research found that the polymerization rate of rare-earth compounds is still
much higher than that of aluminum alkoxides. Additionally, according to research,
enzymatic polymerization is more environmentally friendly than chemical synthesis
methods are. Enzymatic reactions require a mild environment, and enzymes are efficient,
inexpensive, and have high specificity. Chemical reactions require a single reactant to
avoid side reactions.
Steps in ROP of PLA
- lactic acid is dehydrated to produce oligomers at temperatures of PLA 160 °C for 2 hours
- the system is heated to a temperature of 220 °C and a reduced pressure of 200 mmHg.
The condenser is maintained at approximately 90 °C in order to prevent solidification of
the product, for 4 hours of reaction. The lactide is then obtained by distillation, and the
solid phase recovered in condensing flask. The crude product was washed with cold water,
separated by filtration and then dried overnight at a temperature of 40 °C.
- the lactide produced is mixed with the catalyst (1wt%) at a temperature of 140 °C for 2
hours and the PLA produced.

2.2. Direct Polycondensation and Coupling

Although the cost of the condensation-polymerization method is low, it cannot directly

synthesize polymer PLA. Rather, part of the cost corresponds to the coupling agent and
esterification accelerator used in the synthesis process. The synthesis step is divided into
two steps. The first step is the dehydration condensation of hydroxyl and carboxyl groups
at equimolar concentrations to produce low-molecular-weight polylactic acid. Next,
coupling agents and esterification adjuvants need to be added. Their addition can modify
the PLA and help amplify the chain. To obtain a high-purity, low-molecular-weight
oligomer final product with no residual metal or catalyst, it is necessary to introduce
triphosgene to remove the adjuvant and byproducts in the reaction. However, in addition to
higher economic costs, this method uses flammable solvents, thus increasing safety risks.
Although later studies found that new chain extenders could replace the esterification of
the above-mentioned adjuvants, there is still the problem that chain extenders and polymer
impurities are toxic and nonbiodegradable. Although the azeotropic dehydration
condensation method avoids the use of adjuvants during the synthesis of PLA, the
disadvantage of this method is that dibasic acids and glycols are used as solvents in the
reaction while the catalyst remains. First, lactic acid is distilled under reduced pressure at
130 ◦C for 2–3 h to remove most condensed water. The catalyst and diphenyl ether are
added to the reaction. This is passed through a molecular sieve and returned to the
container for another 30–40 h at a temperature of 130 ◦C. The polymer can then be
separated or dissolved and precipitated for further purification. In the subsequent
production process, due to the effective removal of water, the increase in the boiling point
of the solvent results in an increased polymerization rate. After testing a variety of
catalysts, it was found that tin compounds have higher catalytic efficiency. In addition, the
content of impurities hinders the synthesis to a certain extent. In follow-up industrialization
research, it was demonstrated that it is possible to remove the catalyst to a great extent
without degrading the polymer. However, the toxicity and nonbiodegradability of the
remaining catalyst can cause irreversible damage to the human body, so it cannot be
applied in the medical field.

2.3. Film Formation

The condensate obtained from ROP or coupling is converted into pellets after melting at
150 C. The pellets are then extruded into different forms. Films of polymer are made using
cast film extrusion and blow moulding techniques.
Blow Molding

The plastic melt is extruded through a die, usually vertically, to form a thin walled tube.
Air is introduced through a hole in the middle of the head to blow up the tube like a balloon.
To cool the film on top of the die, an air ring is installed that strikes the hot film to cool it. The
film tube is then moved upward, cooled by air until it passes through a plurality of nip rolls
where the tube is flattened to create a so-called „flat” film tube. Then, this flat tube is run back
into the extrusion tower through more rollers. At the higher exit lines, the air inside the bubble
is also exchanged. This is known as IBC (Internal Bubble Cooling).

The flat film is then either kept as such, or the edges of the strip are cut out to produce two
sheets of flat film and wound onto spools. When stored as a web, flat film is made into bags by
compaction across the width of the film and cutting, or perforation, for each bag. This is done
either in conjunction with the blown film extrusion process or at a later stage.

Typically, the coefficient of expansion between the die and the blown film tube will be 1.5
to 4 times the die diameter. The subsidence between the thickness of the melt wall and the
thickness of the cooled film occurs both in the radial and longitudinal directions and is easily
controlled by the change in the air volume inside the bubble and the change in the exit velocity.
This gives blown film a better balance of properties than traditional cast or extruded film, which
is only stretched along the direction of extrusion. Blown film generally has a better balance of
mechanical properties than cast or extruded films because it is drawn in both the transverse and
machine directions. Mechanical properties of the thin film include tensile and flexural strength,
and toughness. The nearly uniform properties in both directions allow for maximum toughness
in the film

Figure 4: Schematic representation

of blown film extrusion

The efficiency of blown film extrusion can be improved by minimizing the temperature of
the polymer melt. Reduction of the melt temperature causes the melt to require less heating
in the extruder. Normal extrusion conditions have a melting temperature at about 190° C
despite the fact that the temperature of the melt only needs to be about 135°C

Cast Extrusion
To extrude a thermoplastic polymer, granules are fed into a heat-regulated cylinder inside
which an endless screw is turning. Due to the combined effect of the kneading action and
heat, the granules are turned into a homogenous mix looking like a paste which is then
given the desired shape by the die. a thin film is extruded through a slit onto a chilled,
highly polished, turning roll where it is quenched from one side. The speed of the roller
controls the draw ratio and final film thickness. The film is then sent to a second roller for
cooling of the other side. Finally, the film passes through a system of rollers and is wound
onto a roll.

Figure 5: Cast Film Extruder

3. Properties of PLA Films
3.1.Sealing Properties

The packaging material used must be sealed securely. A good seal prevents material and
volatiles from leaking out. It reduces the possibility of microbial contamination while also
reducing variations in head space gases and moisture content. As a result, in order to prevent
quality changes and assure the safety of food items, the integrity of the seal area must be
considered in flexible food packaging.

There are various techniques for sealing flexible packaging film. These procedures can
involve the application of a cold-seal adhesive coating to the inner surface of the packing
sheet or the melting and combining of sealant layers utilising heat sealing.

Heat sealing is the most prevalent method for shaping and closing plastic packaging materials
in the food business, and it has been used for decades.

Figure 6:Mechanisms behind the heat sealing of flexible packages

 3.2. Barrier properties

Small molecules from the inside and/or outside of a package can travel through polymer
films, affecting the quality of packed goods. Aroma is one of the most important quality
requirements for a wide range of food and consumer goods. Flavor loss, scalping, and/or
contamination can occur as a result of aroma transmission via packing materials, resulting in
poor product quality.

Specific gases, aromas/odors, moisture vapour, water, oil, and grease should not penetrate a
barrier coating or film applied to paper-based food packaging, as this might impair the
sensory and sanitary integrity of the packed food product. Due to the oxidation or rancidity of
unsaturated fats, gases, particularly oxygen, can cause discoloration, off-flavors, and texture
changes in food. Hydrophobic Petro-based polymers such as PP, PVC, and PE are most
commonly employed in food packaging as films or paper coatings for water vapour
resistance. Grease resistance and water hydrophobicity are the major barrier qualities needs
for short-term retail applications such as pizza, burgers, cookies, ice cream, and so on.

3.2.1. Water Vapor Permeability

The transmission rate of water vapor through thin film layers of biopolymers quantifies the
barrier of biopolymer against moisture. It is measured by placing the test sample at standard
test conditions and purging humid air through it. The transmission rate calculates the amount
of vapor passing through the film in unit time. Multiple standard conditions are defined by
the standard regulating authorities. Selection of correct conditions depend on film properties.
Transmission rate is affected by thickness and density of film and test chamber envrionment.
Material hygroscopicity affects the rate at which moisture transmits. Hence a better barrier
can be achieved by having less porous, smooth surfaces.

3.2.2. Oxygen Permeability

Oxygen barrier is another important characteristic desired in paper coatings. Inherently paper
products have poor barrier and hence the coatings must provide barrier against oxygen
movement to keep food packed inside intact. Dense structure with small pore sizes are
favorable to keep transmission rates low. OTR values are dependent on temperature and
relative humidity maintained while conducting the tests. Like WVTR, multiple standards are
defined for measuring oxygen transmittance as well.
 3.3. Mechanical Properties

The mechanical properties of thin films are evaluated to study the material properties such as
Young’s Modulus of elasticity and tensile strength. They convey more information about the
intermolecular bonds and intermolecular forces being experienced at the atomic level in the
formulation to be used as paper coatings. Yield strength, ultimate strength, elongation at
break and stress-strain relation of the material define its mechanical properties. Young’s
modulus, which is the ratio of stress to strain, is the ratio quantifying the elasticity of a
material. Plastic materials show permanent deformations and do not restore to their original
shapes. Brittle polymer films have high young’s modulus values, as they do not elongate
much and rupture under stress without being much deformed. Apart from tensile strength,
which measures the force a material can withstand in the axial direction, burst strength gives
the amount of force required to break film by applying force perpendicular to the film/sheet.
𝐹
𝜎 = , where σ is the stress experienced by the film
𝐴

𝛿
𝜀 = , where ε is strain and δ is elongation in film
𝐿

𝜎
𝐸=
𝜀

Graph 1: Stress-Strain curve for

different blends of PLA plasticizers

Among different paper grades, kraft paper has high burst strength. Adding wet and dry
strength additives further increases their strength. Using biopolymer coatings allows to
increase their strength as the coatings form a thin film of their own and adhere to the paper
surface. This results in increased strength of the coated paper and also makes it more flexible.

3.4. Crystallinity
Behaviour of polymeric films is influenced by atomic arrangement at their lattices.
Amorphous structures have randomly arranged atoms and therefore less strength. This short
chain random structure allows them more flexibility as compared to crystalline structures.
Crystalline films on the other hand have high strength and strong intermolecular forces,
making the film tough to break. Elastic films having crystalline structure are therefore
laminated with amorphous films that could be sealed easily. Biopolymer films have weak
intermolecular forces and hence their crystallinity becomes an important characteristic to
control. Different plasticizers are used to alter the surface properties and change crystallinity
of the film. This also controls the adherence of coating to the paper substrates. Usually,
crystalline films have less surface tension compared to amorphous materials owing to their
smooth texture which allows less interlocking between molecules.

3.5. Molecular Weight

Molecular weight of the film/coating is another important characteristic property which is

affected by the degree of polymerization. Higher average molecular weight tends to have
higher tensile strength. Bigger macromolecules have high tendency to branching. This makes
their intermolecular bonding stronger and increases their strength.

3.6. Glass Transition Temperature

Glass Transition Temperature, Tg, is defined as a temperature at which resin changes from a
rigid glassy material to a soft material. It is not a melting point but involves the material
becoming “softer”. This temperature (measured in °C or °F) depends on the chemical
structure of the resin and can therefore be used to select the right resin depending upon the
end-use of coatings.

Physically, the glass transition temperature is the point at

which polymer chains gain enough energy to increase
their mobility within the polymer matrix. The transition
from the glass to the rubber-like state is an important
feature of polymer behavior, marking a region of
dramatic changes in the physical properties, such as
hardness and elasticity of the coating.
The Tg is a very intricate concept and is not represented
by a single value, even though it is an excellent starting
point for understanding coating dynamics.
4. Blends and Copolymerisation
The critical factors that influence the properties of polymers include chemical components,
compositions, morphological structure and so on. In PLA synthesis, most studies focus on the
variety and amount of hydrolytic groups, the flexibility and crystallinity of the molecular
chains, and the hydrophilic groups. The modification of PLA includes the copolymerizing of
the lactide with other lactone-type monomers, a hydrophilic macromonomers (polyethylene
glycol (PEG)), or other monomers with functional groups (such as amino and carboxylic
groups, etc.), and the blending PLA with other materials. The copolymerization of lactide
with other lactone-type monomer polyglycolide can improve PGA’s high crystallinity, high
melting point, and poor solubility. Thus, the copolymerization product (poly-lactic-glycolic
acid (PLGA) ) exhibits better properties (lower crystallinities and melting temperature (Tm))
than PLA and PGA. The degradation characteristic of PLGA could be adjusted by controlling
the ratio of LA to glycolic acid (GA) in the feeding dose. The PLGA composed of 50:50

Figure 7: PLA PEG copolymer

(LA:GA) is entirely amorphous. The degradation rate of PLGA is faster than that of PLA and
can be increased by increasing the GA content. However, the solubility and toughness of the
copolymer are also limited by the composition. In order to further adjust the degradation rate
of PLGA and the flexibility of the polymeric chain, a third component – caprolactone (CL)
was introduced into PLGA. The poly(glycolide-co-lactide-co-caprolactone) tri-component
copolymer (PGLC) was synthesized by ring-opening copolymerization of glycolide, L-
lactide, and ε-caprolactone in the presence of stannous octoate. By adjusting the component
ratio of the three monomers, copolymers with different degradation rates could be obtained.
Also, as the glass temperature (Tg) of PCL is getting lower, the Tg of PGLC decreases as the
CL and GA content increase. The mechanical property measurement showed that the
increasing of the CL content resulted in the toughness reduction but enhanced the flexibility
of the copolymers. The break elongation ratio of the PGLC increased significantly with the
introduction of the CL content. Based on this principal, a series of copolylactides with
different degradation ratio ranging from several weeks to more than two years, as well as
various physical appearances and mechanical properties, could be gained by adjusting the
component ratio of lactide to the other lactone-type monomers and the molecular weights of
the copolymers. However, the hydrophilicity of the copolymer using this method could not be
improved significantly. The use of PEG is hence necessary. PEG is a highly biocompatible,
nontoxic, nonimmunogenic, and nonantigenic polymer with excellent hydrophilicity. It is
known to decrease the attractive forces between solid surfaces and proteins because of its
highly hydrated polymer chains, steric stabilization forces, as well as chain mobility. Such
properties can make a surface highly resistant to biological fouling and reduce protein
adsorption. Since PEG is very soluble in water and many organic solvents, it can also be
easily removed from the tissue. In addition, since it has two hydroxyl groups with reactive
ends, the using PEG as the macromonomer to improve the hydrophilicity and the
biocompatibility of PLA is a good choice. In addition to the copolymerization technique, the
bulk properties of PLA could also be modified by blending with other materials. By blending
PLA with naturally derived dextran, a new kind of biodegradable material, could be obtained.
Moreover, a sponge-like scaffold could be fabricated using solvent-casting and particle-
leaching techniques. In order to obtain a uniform blend of PLA and dextran, hydroxyls of
dextran were protected via trimethylsilyl (TMS) groups to make dextran soluble. A
homogeneous solution of PLA and TMS-protected dextran could be obtained using a mixed
solvent of dichloroform and benzene. The hydrophilicity and cell affinity of the PLA-dextran
blend was improved significantly compared with pure PLA.

Chitosan is a promising natural cationic polymer with good biocompatibility, nontoxicity,

and biodegradability. It is produced by alkaline N-deacetylation of chitin, the most abundant
natural polymer after cellulose. Chitosan has been shown to be useful as a chelating agent,
drug carrier, membrane, water treatment additive, biodegradable pressure sensitive adhesive
tape, wound healing agent, nerve repair, and in other important applications. However, such
biomedical properties of chitosan must be improved for the adsorption of drugs and proteins
and the adhesion of cells to biomedical materials. Thus, in order to improve the properties of
chitosan, a hydrogel was synthesized through grafting D,L-lactic acid onto the amino groups
of chitosan. Because the –NH2 groups of the chitosan were substituted randomly along the
chain, the regularity between chitosan chains was destroyed and the crystallinity of chitosan
hence gradually decreases after grafting. A brush-like copolymer of poly D,L-lactide-
gchitosan was prepared in this way.
 Figure 8: PLA Chitosan

copolymer

Isomerism in Lactic Acid

Unmodified polylactides are linear macromolecules having a molecular architecture that is
determined by their stereochemical composition. The repeat unit of PLA (72 g mol-1)
contains one stereocenter that is either L(S) or D(R) in configuration. Microorganisms mainly
produce L-lactic acid, and no major sources of D-lactic acid are available, although some
lactobacilli are reported to produce D-lactic acid. The repeat units are either added as dimers
during the ring-opening lactide polymerization or are added to the final polymer as lactic acid
monomers via direct condensation polymerization, as explained in the previous section. Both
mechanisms involve acyl cleavage of the ester bond with preservation of chirality.
mesoLactide possesses a two-fold axis of improper rotation and is therefore optically
inactive. Lactide can be obtained as L,L or D,D enantiomers, commonly called L-lactide and
D-lactide, the meso compound (R,S), and a racemic or equimolar mixture of the L and D
enantiomers, rac-lactide, commonly referred to as DL-lactide. The literature sometime
confuses meso- and rac-lactides, and refers to them as DL-lactide. In the ring polymerization
technique, the lactide stereoisomers are produced from the depolymerization of low
molecular weight poly(lactic acid) using tin catalysis and stereoselective initiators to enhance
the rate and selectivity of the intramolecular cyclization reaction. The molten lactide is
produced in proportions close to statistical expectations from the initial lactic acid isomers
(equal reactivity), wL-lactide ¼ S 2 wD-lactide ¼ R 2 wmeso-lactide ¼ 2RS where S and R
are the original fractions of L-lactic acid and D-lactic acid, respectively, and w is the weight
fraction. Since the initial distribution of lactide isomers determines the potential for
polylactide crystallization, lactide is purified by vacuum distillation. PLA derived from
greater than 93% L-lactic acid can be semicrystalline whereas PLA from between 50 and
93% L-lactic acid is strictly amorphous. Both meso- and D-lactide induce twists in the
otherwise very regular poly(L-lactide) molecular architecture. Molecular imperfections are
responsible for the decrease in both the rate and extent of poly(L-lactide) crystallization.

Figure 8: PLA
Enantiomers and
racemic mixture

Since polylactide production always contains some amount of meso-lactide impurities,

practically all PLAs are made up of L- and D,L-lactide copolymers.It is known that poly(L-
lactide) and poly(D-lactide) form an equimolar stereocomplex crystalline structure (i.e.,
raclactides) having a significantly higher melting temperature (230°C) than the
homopolymers. Dimeric polymerization imparts some order to the otherwise random
distribution of L- and D-stereocenters in PLA chains. Hence, the lactide ring-opening
polymerization process gives a fundamentally different molecular architecture for PLA
polymers derived from lactic isomeric mixtures other than 100% L- and 50/50 D,L-lactic
acid. High molecular weight bulk lactide polymerization should be conducted at high
temperatures (e.g. 190–200°C) to maintain the appropriate viscosity, and at these
temperatures racemization can become an important side reaction. However, a laboratory
scale polymerization of lactide at low reaction temperature such as 120–140°C gives a high
molecular weight PLA. Reactivity among the lactide isomers is slightly different. meso-
Lactide has a higher rate of hydrolysis and a greater tendency to polymerize. The L- and D-
enantiomers have identical rates. Witzke attributed this rate difference to a different
configurational and conformational structure. Energy studies indicate that meso-lactide is
about 1.7 kcal mol-1 more stable than L-lactide. Although not perfect, the assumption of
similar reactivities for lactide production and polymerization is still reasonable, resulting in a
small error in final composition estimations. Nevertheless, the configurational and
conformational differences between meso- and L-lactide result in different physical
properties, such as melting point, solubility and relative volatility. As far as polymerization is
concerned, the role of mesolactide is to provide amorphous polylactide when it is
polymerized with L-lactide. Witzke investigated the molecular architecture of different
lactides and found that poly(L-lactide) is arranged in a syndiotatic manner. Poly- (meso-
lactide) has a structural configuration of repeat units of (RS)-(SR)-(RS)-(SR), which is
syndiotactic in dimers. It has also been reported as having an isotactic structure (RS)- (RS)-
(RS)-(RS). Depending on the preparation conditions, poly(L-lactide) crystallizes in three
forms (a, b and c). The stable a-form exhibits a well-defined diffraction pattern. Analysis of
a-form of poly- (L-lactide) using linked-atom least squares refinements for X-ray fiber
diffraction data, and found that the a-form has an orthorhombic P212121 space group, with a
unit cell containing two antiparallel chains. ‘‘The chain conformation was the 2-fold (15*2/7)
helix distorted periodically form of the regular s(3*10/7 helix)’’.The lattice parameters were
a = 10.66 A˚ , b = 6.16 A˚ , and c (chain axis) = 28.88 A˚ , with a crystal density of 1.26 g
cm-3

5. Applications in Packaging
PLA Packaging Characteristics

• Clarity – clear transparent

• Strength – low impact capacity and brittle
• Ability to be down-gauged
• Alcohol and water resistant
• Not suitable for hot filling
• Compatible with existing recycling systems
• Can be composted, landfilled and incinerated easily
With its classification being generally recognized as safe (GRAS), PLA has been approved
for use in food packaging, including direct contact applications. In addition, PLA is a good
candidate for a variety of packaging applications due to its close similarity to commercial
thermoplastics such as PET. In the last decade, PLA has been developed for a wide range of
primary packaging applications including oriented and flexible films, extruded and/or
thermoformed packages suitable for common applications such as food and beverage
containers, cups, overwrap, blister packages, as well as coated paper and board. Recently, a
Danish dairy company has used PLA, that was claimed to be biodegradable, for yoghurt cups.
Other commercial examples include the use of PLA for the production of lunch boxes and
fresh food packaging, and containers for packaging of bottled water, bottled juices and
yogurts. Blends of PLA with starches, proteins, and other biopolymers have also been studied
in order to develop fully renewable and degradable packaging materials.

PLA antimicrobial packaging

The potential of PLA for use in antimicrobial packaging applications investigated in recent
years by a number of researchers. There are also a number of patents worldwide on PLA-
based materials containing antimicrobial agents. Several substances such as organic acids,
bacteriocins (for example, nisin), plant extracts (for example, lemon extract), essential oils
and extracts (for example, thymol), enzymes (for example, lysozyme), chelating agents (for
example, EDTA), metals (for example, silver) have been incorporated into PLA to provide
antimicrobial activity. In particular, PLA with the addition of natural antimicrobial agents
such as nisin, lysozyme, and silver zeolite has
shown inhibitory effects against selected
microorganism such as Listeria monocytogenes,
Escherichia coli, Staphylococcus aureus,
and Micrococcus lysodeikticus. Natural
antimicrobial agents have also been incorporated
into coatings on the surface of PLA and these
were shown to be effective against spoilage and
pathogenic microorganisms. According to
Jamshidian and others (2010), only a few studies
have investigated the potential of PLA in general AP applications although there are a
number of examples that use PLA in antimicrobial food packaging applications.

Current technologies enable effective antimicrobial packages to be prepared from PLA that
has been blended with different compatible materials and plasticizers. The consumer
preference for natural food products with few or no preservatives, with minimal microbial
contamination while using sustainable packages has generated a growing interest in the use of
PLA in antimicrobial packaging. An example of a commercial
antimicrobial PLA packaging product is Antipack™ produced by
Handary in Belgium, which is a film manufactured from a PLA-
/starch-based material incorporated with an antifungal agent. This
product is claimed to prevent the growth of yeast and mold during the
shelf life period by gradually releasing chitosan-containing
natamycin onto the surface of solid foods such as cheese, fruits,
vegetables, meat, and poultry.

Furthermore, it is believed that PLA can perform as a suitable Figure 11:Packaging application of
carrier of antimicrobial agents without showing any indivertible PLA film
impact on the compositing and potential biodegradation process.
This is possible if the rate of dissipation of the antimicrobial agent or the controlled release
during the shelf life of the system as a packaging material is fully understood, systematically
performed, and accurately controlled. Therefore, the study of antimicrobial agent migration in
the system will be very important in the future to ensure the agent is dissipated before the
packaging materials is disposed of in landfill.

Potential Packaging Applications

As these biopolymer films are mechanically and physio-chemically equivalent to synthetic

non biodegradable films, they have the potential to be used as flexible packaging materials.
Their cost and controlled degradation remain the obstacle but with technological
advancements these could be eliminated.

• Food and Beverages

• Healthcare and Cosmetics

• Agricultural Products

• Consumer and Household Products

6. Top Manufacturers of PLA Resins/Films

As Poly lactic acid is one of the most promising bio-polymer, more companies have tried to
industrially manufacture it using various compositions. Different brand names are used to sell
with the marketing mainly focused on green nature of the material. Worldwide 250000 tons
of annual production was reported in the year 2017. China is the leading producer of pla
films.

Figure 12: Major Manufacturers of PLA film

1. USA: NatureWorks
NatureWorks is the largest polylactic acid manufacturer in the world. It was founded in 1997
by Dow Chemical and Cargill. At that time, it was called Cargill Dow polymers. Later, it was
renamed NatureWorks company. NatureWorks built the world's largest polylactic acid
production plant in 2001, and is the only enterprise with an annual output of 150000 tons of
polylactic acid in the world. It also plans to build a 70000 ton branch plant in Southeast Asia,
mainly made of corn starch.
2. Thailand: Total Corbion
Total corbion is a joint venture company established by Total and Corbion. In 2017, it
invested in a 10000 ton PLA plant in Thailand and officially put into operation in December
2018. Total corbion's PLA plant in Thailand has an annual capacity of 75000 tons. At
present, it is the world's largest lactide supplier and the world's second largest PLA supplier.
3. The Netherlands: Synbra Technology
Synbra company of the Netherlands has a production line of 1000 tons. Synterra, a heat-
resistant biological resin mainly made from plant (sugarcane, etc.), has higher heat resistance
than traditional polylactic acid, and is known as "the second generation polylactic acid". Its
new plant has an annual capacity of 5000 tons of polylactide.
4. Belgium: Futerro
Futero, Belgium, was founded in September 2007. At present, it has a polylactic acid plant
with an annual output of 1500 tons.
5. China: Zhejiang Haizheng Biomaterials Co., Ltd
At the end of 2005, Zhejiang Haizheng Biological Co., Ltd. officially put into operation its
first 5000 ton PLA production line, with a production capacity of 25000 tons by 2021, and
another 50000 tons of PLA production capacity is under construction.
6. China: Shenzhen eSUN Industrial Co., Ltd.
eSUN was originally founded in Shenzhen in 2002, which is dedicated in R&D and industrialization
of bio-degradable polymers, such as PLA and PCL. At present, it has built an annual production
capacity of 10000 tons of polymers, 15000 tons of lactic acid esters, 5000 tons of polyols and 1500
tons of 3D printing materials.

7. China: COFCO Biotechnology Co., Ltd

Jilin COFCO biomaterials Co., Ltd., established in July 2015, is a modern enterprise focusing on the
production of bio based materials polylactic acid (PLA). The project has an annual output of 30000
tons of bio based raw materials (polylactic acid) and 30000 tons of bio based products. Its polylactic
acid production technology is based on the patented PLAneo® technology developed by
Thyssenkrupp Industrial Solutions.

8. China: Shanghai Tong-jie-liang Biomaterials Co.,LTD.

Shanghai Tong-jie-liang Biomaterials Co.,LTD. is a new material high-tech enterprise engaged in the
research and development, production and sales of polylactic acid materials. At present, it has a
production capacity of 1000 tons of polylactic acid.

9. China: Jiangsu Supla Bioplastics Co., Ltd

Jiangsu Supla Bioplastics Co., Ltd is a high-tech enterprise focusing on bio based fully degradable
polylactic acid (PLA) materials, integrating R & D, production and sales. The 50000 ton PLA project
was put into operation in September 2015.

10. China: Jiangxi Academy of Sciences Biological New Material Co., Ltd
Jiangxi Academy of Sciences biological new materials Co., Ltd. was renamed from Jiujiang Academy
of Sciences Biochemical Co., Ltd. It has advanced lactic acid fermentation, lactide preparation and
polylactic acid polymerization technology. The first 1000 ton polylactic acid plant was completed and
put into operation in 2017.

Figure-13: TDS screenshot of

Natureworks Ingenio
7. Conclusion
While more efforts to create a system of correct disposal of lactic acid polymer based
films are required, they are still the most potential bio based polymer and hence can be
used as primary substrates that can be blended of grafted upon by other degradable
material which increase its mechanical, barrier, sealing and printability properties. Use of
PLA films as active packaging material is being researched upon as well. These can be
used as edible films and are regarded as safe by food safety authorities. Relatively poor
properties as compared to PET, LDPE and PP are hindering the full fledged usage of
PLA flexible films. Currently they are being used as trash bags or compostable bags as
they can directly be incinerated or composted directly. Apart from films, they are used in
compositions of bio compostable straws, cups, cutlery items etc. Further work on blends
and copolymers of PLA could enable it to be used as primary packaging flexible
materials.
8. References

• Advances in barrier coatings and film technologies for achieving sustainable

packaging of food products – A review- Preeti Tyagi , Khandoker Samaher Salem,
Martin A. Hubbe, Lokendra Pal
• Synthesis and Characterizations of Poly (Lactic Acid) by Ring-Opening
Polymerization- Savioli Lopes, Jardini, Maciel Filho
• Biodegradable packaging materials conception based on starch and polylactic acid
(PLA) reinforced with cellulose- Fatma Masmoudi, Atef Bessadok
• https://www.uppi.com/materials-for-packaging/pla-plastic/
• An overview of polylactides as packaging materials- Susan Selke, Rafael Auras
• A Review of Poly(Lactic Acid)-Based Materials for Antimicrobial Packaging- Intan
S. M. A. Tawakkal, Marlene J. Cran,Joseph Miltz,Stephen W. Bigger
• Preparation and properties of plasticized poly(lactic acid) films- Nadia
Ljungberg , Bengt Wesslén
• http://www.polymerdatabase.com/Films/PLA%20Films.html
• Synthesis and Biological Application of Polylactic Acid- Ge Li, Menghui Zhao, Fei
Xu, Bo Yang, Xiangyu Li, Xiangxue Meng, Lesheng Teng , Fengying Sun and
Youxin Li
• Poly (Lactic Acid) Films in Food Packaging Systems- Ayse Tulin, Ozge Sufer and
Yasemin Sezer