PLASTIC

PACKAGING
 Type of plastics used in
food packaging

Food contact and

Plastic barrier properties
Packaging Product

Plastic Application
Classification
 EU Directive (reference 2001/62/EC) defines plastics as being: ‘organic macromolecular compounds
obtained by polymerisation, polycondensation, polyaddition or any similar process from molecules
with a lower molecular weight or by chemical alteration of natural macromolecular compounds’

ASTM D833
▪ “ plastic” is used to describe the The utility of flexible sheet materials depends
easily deformable state of the on the properties of a special kind of molecular
material, structure: long, flexible molecules interlocked in
▪ “plastics” to describe the vast to a strong and nonbrittle lattice
range of materials based on
macromolecular organic
compounds. Plastic
Differences in the chemical constitution of the
At some stage of monomers, in the structure of the polymer chains
their manufacture, plastic can be and in the interrelationship of the chains
formed to shape by flow, aided in determine the different properties of the various
many cases by heat and pressure polymeric materials.
.

From a technical viewpoint, plastics is a generic term for macromolecular organic compounds
obtained from molecules with a lower molecular weight or by chemical alteration of natural
macromolecular compounds.
 Why plastic packaging
Flowable and mouldable Provide choices in respect of
under certain conditions, to transparency, colour, heat sealing,
make sheets, shapes and heat resistance and barrier.
structure

Lightweight, not prone to

Generally chemically inert,
though not necessarily
PLASTIC breakage and do not
result splintering
impermeable

Shapes and designs which Available in a wide range of pack

present food products cost aging structures
effectively
Can be integrated with food
processing technology
 Plastic Classification
Plastic
Classification

Material Manufacturing method Physical Properties

Converted Synthetic Condensation Addition

Thermoplastic Elastomer Duroplastic
Natural Product Product reaction reaction

Biobased packaging Petroleum based Two different reactive The molecules of the Uncross Chemically Chemically
material plastic : functional groups can starting materials linked plastic wide- close-meshed
▪ Natural polymer ▪ Polyolefins polymerize without an contain double bonds up to their meshed plastics
(agriculture resource) ▪ Polyester further external which are broken decomposition crosslink up to the
▪ Microbial polymer ▪ Polystyrene assistance with the with the help of temperature plastic that are decomposition
[P(3HB)], PHBV and ▪ Polyvinyl chloride help of an initiator or a initiators or catalysts. elastics from temperature
PHA ▪ Ethylene vinyl catalyst or two different The resulting free lower temperature and
▪ Bio-derived monomer ▪ alcohol starting materials radicals then undergo (below 00C) up to normally
polymers ▪ Polyamide (monomers), having a chain reaction to for decomposition amorphous
Polylactic acid (PLA) each two identical a macromolecule. temperature
functional groups.
 Plastic Packaging
Product

Flexible Rigid
packaging packaging

comprising films, comprising bottles and

made by both cast other containers, made by
and film blown thermoforming and blow
processes. molding processes.

· Liquid food (oil, ghee, water, lassi,

dahi, milk, etc.).
· Plastic bag · Semi-liquid food (sauce, chutney).
Solid powders (milk solid, coffee,
· Sachets
atta, flours, etc.).
· Pouches
· Solid grains (daal, cornflakes,
· Overwraps
beans, breads, roti, paratha, etc.)
and namkeen (mixtures, popcorns,
chips, biscuits, dry fruits, etc.).
· Flat bottom pouches for drinks
(juices, tea, coffee, etc.)
Properties of rigid and flexible packaging
 Plastic Packaging
Manufacture

Flexible packaging Rigid packaging

Sheet Machined Mould

Multilayer Monolayer Injection molding Blow molding

Coextruded Laminated Thin wall injection Injection Extrusion Stretch

Single film
film film molding Blow Blow Blow
Molding Molding Molding
Two or more layers of Bonding together Plastic bags are made
Molded plastic products are A polymer is Shape by
plastics in molten two or more by folding, cutting and A continuous
obtained by pushing the injected and injection or
condition are plastics or bonding sealing with welded tube of
molten thermoplastic into a molded around a extrusion molding
combined during the plastic to another seams which are also softened
mold and then by cooling and blowing stick, then reheated,
film manufacturing. material such as cut in the same polymer is
solidifying it while molten is which causes
paper or aluminum operation. trapped
transferred to between the the plastic
the blowing mold two halves of a molecules to “line
mold. up.”

• Ethylene vinyl alcohol (EVOH) • Polyethylene (LLDPE, LDPE and HDPE)

• Fluoropolymers (PTFE) • Polypropylene (PP, BOPP)
• Cellulose-based materials • Polyesters (PET)
• Polyvinyl acetate (PVA). • Nylon (PA6, PA66 and PA11)
Type of plastics used in food packaging

Semicrystalline polymer
Easy processable with
high toughness and flexibility. It has good
barrier properties for moisture and water
vapor and high chemical resistance. High flammability and possesses
01 lower thermal stability compared
07 to some of the plastics used in
packaging.

02
Higher crystallinity in it gives high
stiffness, hardness, tensile strength,
opacity, barrier properties and heat
and chemical resistance 06 Polyethylene Low barrier properties to
ward gases, oils and fats
03 .

Free of odor and toxicity and has excellent 05

Depending on the type of polyethylene,
electrical insulation properties with easy heat 04 the density varies from 0.91 g/cc for
sealability. LLDPE to 0.948 g/cc for HDPE
 ➢ Low-Density Polyethylene (LDPE)

LDPE is so named because it contains

a substantial amount of branches which The high pressure polymerization
hinder the process of crystallization, process employed for the manufacture of
resulting in relatively low densities LDPE leads to the development of
(0.9–0.94 g/cc). both short chain and long chain branches

LDPE is preferred in film applications

due to has toughness, flexibility and
relative transparency with good heat
sealing capacity, flexible lids and
bottles.
• Bags for bread, frozen foods, fresh produce
and household garbage
• Shrink wrap and stretch film
• Coatings for paper milk cartons and hot and
cold beverage cups
It has excellent resistance
to chemicals like acids,
bases and vegetable oils.
 ➢ High-Density Polyethylene (HDPE)

To improve heat sealability, HDPE can be

High degree of crystallinity and hence HDPE is injection moulded for closure, coextruded with LDPE to achieve
higher densities (0.940.97 g/cc) crates, pallets and drums, and peelable seals where the polymer layers
along with better mechanical rotationally moulded for intermediate can be made to separate easily at the
properties. bulk containers (IBCs). interface of the coextrusion.

• Excellent solvent resistance HDPE is used to make different types of bottles/containers.

• Compared to other grades of PE, higher tensile Bottles without any colorants are translucent, have excellent
strength obtained. barrier properties and stiffness and are good candidates for
• Relatively stiff material with useful temperature packaging products with a shorter shelf life such as milk.
capabilities.
 ➢ Polypropylene (PP)

Strong and has Non-toxic, easily Ethylene propylene It has high resistance Low moisture vapor
excellent chemical processable elastomers, produced by to chemicals but has transmission rate toward
resistance with polymer having copolymerizing poor oxidative acid, alkalis and most
high melting point good dielectric propylene with ethylene, stabilities. Addition of solvents, cost-effective
making it good and insulation show improved antioxidants is there plastic, having density
for hot-fill liquids. properties, resistance to heat and fore necessary for between LDPE and HDPE.
excellent clarity oxidation, as well as stability in application It possesses high
and good favorable tensile and involving oxidative thermal resistance due to
mechanical tear properties environments. the methyl group in the
properties. main chain.
 Capability for hot filling
Optical clarity and smooth Linear chain thermoplastic polymer due to which
surfaces for oriented films it can be easily converted from amorphous
01
and bottles 12 02 phase to crystalline phase by annealing or
stretching above glass transition temperature

Good barrier properties

11 03 Amorphous PET is highly transparent
gases like oxygen, water
and carbon dioxide but is vulnerable to thermal degradation
.

Polyethylene Crystalline PET is high in strength,

High impact capability 10 04
and shatter resistance Terephthalate rigid, dimensionally stable, water
resistance and thermally stable
(PET)
Superior gas barrier properties
making it an ideal choice in
09 05 Crystalline PET possesses good
several food packaging applications resistance to chemicals but not at
good as PE or PP
08 06
Exists in either amorphous or crystalline
form. This broadens the range of 07 High glass transition temperature and
applicability to a wide variety of packaging melting point and is 100% recyclable
applications Excellent solvent resistance
 ➢ Polystyrene (PS)
It has high transparency (clarity). It is PS film has a low barrier to moisture vapour
stiff, with a characteristic crinkle, and common gases, making it suitable for
suggesting freshness, and has a packaging products, such as fresh produce,
deadfold property. which need to breathe

Blending PS with styrene butadiene copolymer,

Easily processed by foaming SB or SBC, an elastomeric polymer result
to produce a rigid lightweight brittle in rigid or semi-rigid container. The blend
material which has good is known as high-impact polystyrene or HIPS.
impact protection and thermal
insulation properties

HIPS produces a tougher material. It is

translucent and is often used in a white
pigmented form. The sheet can be
HIPS used with PE, PP, PET, PVdC and EVOH by thermoformed for short shelf life dairy products
multilayer sheet extrusion applied in dairy products,
margarine, jam, fruit compote, fresh meat, pasta, salad
 Food contact and
barrier properties

Change in
Migration Permeation
flavor

migration of additives,
residues and monomer permeation of gases, sorption of components,
molecules from the vapours and permeant including volatile flavour
packaging material into molecules from the compounds and lipids,
the food environment into the into the packaging in a
pack headspace and vice process often referred to
versa as scalping.

Possibility that coatings and 3 part process permeation film : Flavour may be masked or chemically
additives used to facilitate • solution/absorption of penetrant changed by any ingress of off flavours
manufacture and use of the (vapour or gas) into the polymer surface and aromas from the external environment
plastic may interact with the food • migration/diffusion of penetrant through by permeation (transmission) through, or
polymer(s) by migration of contaminating ingredients
• emergence/desorption of penetrant from From the packaging material.
opposite surface of polymer.
Index of common off-flavors and their descriptors
 The influence of a sensory active component from packaging to
product is largely determined by the following parameters:

Concentration of
sensory threshold diffusion rate of
component in component in food
packaging material
level of component

solubility of component in
packaging material (partition type and intensity time and temperature
gas phase/packaging of food aroma of storage
material);

solubility of component diffusion rate of ratio of amount of

in food (partition gas component in packaging material to
phase/food); packaging material amount of food
 Application
Packaging needs can be considered in terms of:
• protection of the product – quality, safety etc.
• appearance – sales promotion, pack design etc.
• production – extrusion, forming, printing, packing etc

Ranking of various films with respect to specified properties

Plastic used in food packaging