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PVDC homopolymer has melting point of 198-205 C and decomposes at around
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210 C, making it difficult to process, while copolymers of PVDC have lower Tm of
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about 140-175 C, making melt processing feasible. However, because of narrow
range of feasible processing temperatures for PVDC, its coextrusion with polymers
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that require high processing temperatures such as nylon 6 (260-290 C) and PET
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(280-310 C) and others becomes difficult.
Strengths: Excellent transparency, outstanding chemical resistance, Excellent
barrier to gas, high fats, vapour, odours, oils and greases which extend the shelf life
and conservation of foods, FDA compliant, good sealability, easily printable,
Suitable for transparent applications, outstanding heat sealing properties help
materials such as paper, cellophane and other plastics.
Limitations: Toxicity of its combustion smoke, Poor UV resistance
Applications: Films for food packaging of confectionary, dehydrated foods, dairy
products, sausages, meat, smoked fish, and dried products such as herbs, spices,
tea and coffee, Pharmaceutical blister packaging, Films for thermal insulation,
sensitive electronics.
16) Polystyrene (PS):
Polystyrene is an amorphous, glassy (completely transparent) polymer that is rigid
but has inferior resistance to impacts and relatively inexpensive. Unfilled
polystyrene has a sparkle appearance and is often referred to as crystal PS or
general purpose polystyrene (GPPS).
Density 1.04 - 1.05 g/cm 3
Glass transition temperature 90 °C
Max / Min continuous Service temperature 65 - 80 °C / 20 °C
Melting Temperature 180 - 220 °C
Polystyrenes possess good flow properties can easily be blow and injection
moulded, extruded or thermoformed.
Drying is normally not required but for high transparency and gloss requirement can
be pre-dried for 2 hours at about 80°C.
Injection Moulding: mould temperature between 30 and 50°C recommended and at
10°C for thin wall objects moulded at short cycle times. Mould shrinkage lies
between 0.4 and 0.7% depending on the grade used.
Strengths: Clear glass transparent, rigid, high stiffness, low cost, very good optical
properties and dimensional stability, easy processablity, good electrical properties,
low dielectric loss, excellent resistance to gamma radiation, FDA compliant
Limitations: Brittle at room temperature, Poor mechanical properties above 70°C,
Poor chemical resistance especially to organic solvents, Susceptible to UV
degradation, highly flammable
Applications: Thermoformed disposable trays for vegetables and fresh meat, egg
packaging, tea- coffee cups, pens, lighting industry, gift articles, CD jewel boxes,
disposables cutlery like spoons, knives, Small medical items like Petri dishes,
waste canisters. As film, PS is used for the over wrapping of fruits and vegetables.
17) Expanded Polystyrene (EPS):
Is manufactured by heating the pellets in steam with suitable blowing agent such as

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