4. LDPE
• Polymerization of ethylene gas under
high pressure and temperature
• Density = 910 to 940 kg/m3
• Soft, slightly translucent flexible material with
waxy feel
• Resistance to chemicals
• Good barrier properties to water vapor but less
to oxygen
• High permeability to volatile oils
• Good heat sealing properties - Laminating layer
5. HDPE
• Linear thermoplastic
• Density = 941 to 965 kg/m3
• Stiffer and harder
• Tensile and burst strengths – higher
• Impact and tear strengths – lower
• Better resistance to oil and grease
• Excellent moisture protection
• Decreased gas permeability
• Heat sealing is difficult
6. LLDPE
• Stronger and tougher than LDPE
• Absence of long chain branches
• Density = 900 to 935 kg/m3
• Stiffer
• High tensile strength, puncture resistant
• Combined features of LDPE and HDPE
• Improved chemical resistance
• Improved performance at low and high
temperatures
• Better heat sealing properties
• Greater resistance to environmental stress
cracking
7. POLYPROPYLENE
• Linear polymer containing little or no
unsaturation
• Lower density (900 kg/m3)
• Higher softening point (140 to 150°C)
• Low water vapour transmission
• Medium gas permeability
• Good resistance to greases and chemicals
• Good abrasion resistance
• Good gloss and high clarity
8. POLYSTYRENE
• Addition polymerization of styrene
• Low barrier properties
• Can be blown, extruded, thermo formed and
injection moulded
• Used for packing vegetables and fresh meat
on trays, yoghurt in cups, over wrapping of
fruits and vegetables.
9. PVC
• There are two types – rigid and
plasticized.
• Good moisture, gas barrier properties and
resistance to fats.
• Packing butter or margarine, and for making
transparent bottles for mineral water, edible
oils, fruit juices, carbonated beverages and
beer
• The plasticised form is used for packing meat,
fruits and vegetables and for shrink wrapping
10. POLYVINYLIDENE CHLORIDE (PVdC)
• Lowest water vapour, gas permeability
amongst all
• Resistance to fats and chemicals
• Used as a coating material on other plastics
• Used for packing dense materials like cheese,
poultry, etc.
11. ETHYLENEVINYL ALCOHOL (EVOH)
• EVOH - copolymer of ethylene and vinyl
alcohol
• Excellent barrier to oil, fat and oxygen
• Replaces glass and metal containers
• Manufacture of bulk bags used for aseptic
packaging, retort pouches and containers
12. PET
• Linear, transparent thermoplastic polymer
• PET bottles
• Great tensile strength
• Excellent chemical resistance
• Light weight, elasticity and stability over a wide range
of temperatures (-60 to 220°C)
• Low permeability to moisture and gases
• Poor sealing property- hence it has to be laminated
with PE.
• PET containers are used widely for packing mineral
water, carbonated and non-carbonated beverages,
syrups, edible oils and liquors.
13. ADVANTAGES OF PLASTICS
• Barrier to water vapor and gases
• Light weight
• Good strength
• Design flexibility
• Resistance to breakage
• Machinability
• Glossy and transparent
• Coloring is possible
• High tensile strength
• High tear strength
• High printability
• Low cost
17. LAMINATING PROCESS
• Combination of two or more webs by bonding
them together
• Adhesives used – EVA
• Wet bonding – solvent or aqueous based
adhesives
• Dry bonding – Adhesive dried on one of the
layers – heat applied while binding
18.
19. COATING
• Extrusion coating - melted thermoplastic
applied onto a substrate such as paper
• LDPE coated milk cartons, juice cartons,
drinking cups
• Advantages over Lamination – handling of thin
films of PE is difficult while laminating
