Polymers

Polymers

Polymers in Commercial Packaging
1. Thermoplastic polymers are widely used in commercial packaging.
2. A thermoplastic is a material that, once heated, can be formed into a variety of interesting shapes using different forming techniques such as blow moulding. When cooled, the shape remains permanent.
3. Thermoplastics can be reheated, softened, shaped and cooled many times over. So they can be recovered and recycled easily.
4. Polymers used in packaging can be identified by an internationally recognised coding system moulded into the base of each product/ package/ printed on the label, this system enable them to be easily recycled.
5. Each polymer has its own useful properties that make it suitable for use in different areas of the packaging industry.
6. Advantages
  1. Easily printed on
  2. Inexpensive
  3. Recyclable
  4. Rigid
  5. Versatile
  6. Tough
  7. Strong
  8. Durable
  9. Water resistant
  10. Easily formed and moulded
  11. Impact resistant
  12. Lightweight
Styrofoam for block modelling
1. Styrofoam is extruded polystyrene foam manufactured for the construction industry for insulating buildings. However it makes an excellent modelling material, especially for block modelling purposes.
2. Available in a range of thicknesses and can be glued together with polyvinyl acetate (PVA) to create larger block sizes and also can be painted with acrylic paints to give a good quality finish.
3. Advantages
  1. High compressive strength
  2. Can be sanded to a high surface finish
  3. Easily cut and shaped with hand tools
  4. Great Rigidity
4. Disadvantages
  1. Can become dinted when using a file or ripped when sanding if care isn’t taken
  2. The surfaces break away quite easily, therefore unsuitable for models that require great detail
  3. Weak
Polyethylene Terephthalate (PET)
1. Properties
  1. Sparkling ‘crystal clear’ appearance
  2. Very tough
  3. Lightweight – low density
  4. Does not flavour the contents
  5. Prevents gas from escaping package
  6. Excellent barrier against atmospheric gases
2. Uses
  1. Carbonated (fizzy drinks) bottles
  2. Packaging for highly flavoured foods
  3. Microwavable food trays
High Density Polyethylene (HDPE)
1. Properties
  1. Highly resistant to chemicals
  2. Tough and hard wearing
  3. Lightweight and floats on water
  4. Good barrier to water
  5. Decorative when coloured
  6. Rigid
2. Uses
  1. Unbreakable bottles (for washing up liquid, detergents, cosmetics, toiletries)
  2. Very thin packaging sheets
Polyvinyl chloride (PVC)
1. Properties
  1. Weather resistant – does not rot
  2. Chemical resistant – does not corrode
  3. Protects products from moisture and gases while holding-in preserving gases
  4. Can be manufactured either rigid or flexible
  5. Good abrasive resistance and tough
  6. Strong
2. Uses
  1. Water and fruit juices
  2. Pharmaceutical products
  3. Food and confectionary
  4. Packaging for toiletries
Low density Polyethylene (LDPE)
1. Properties
  1. Decorative when coloured
  2. Very light and floats on water
  3. Very flexible
  4. Tough and hard wearing
  5. Good barrier to water, but not gases
  6. Good resistance to chemicals
2. Uses
  1. Stretch wrapping (cling film)
  2. Milk carton coatings
Polypropylene (PP)
1. Properties
  1. Rigid
  2. Lightwieght
  3. Excellent chemical resistance
  4. Versatile – can be stiffer than polyethylene or very flexible
  5. Low moisture absorption
  6. Good impact resistance
2. Uses
  1. Food packaging – yoghurt and margarine pots, sweet and snack wrappers
  2. Used for laminating paper and board
Polystyrene (PS)
1. Rigid Polystyrene
  1. Properties
    1. Rigid
    2. Lightweight
    3. Low water absorption
    4. Transparent
  2. Uses
    1. Food packaging – yoghurt pots
    2. CD jewel cases
    3. Audio cassette cases
2. Expanded polystyrene
  1. Properties
    1. Very good heat insulation
    2. Durable
    3. Low water absorption
    4. Lightweight
    5. Excellent impact resistance
  2. Uses
    1. Egg cartons
    2. Cups
    3. Packing for electrical and fragile products
    4. Fruit, vegetable and meat trays
Acrylic
1. Acrylic usually is cast into sheets but is also available in rods and tubes.
2. Acrylic is self finishing and doesn’t need an applied surface finish.
3. Uses
  1. Signage and point of sale displays
4. Advantages
  1. Able to withstand extreme weather conditions
  2. Low cost
  3. Can be clear or frosted
  4. Easy to fabricate
  5. Lightweight
  6. Chemical resistant
  7. Excellent aesthetic properties
  8. Durable and able to resist long term stresses
5. Disadvantages
  1. Cracks are easily formed and spread through the acrylic
  2. Low scratch resistance
  3. Brittleness
Environmental concerns
1. Recycling certain types of polymers can also be unprofitable, i.e. polystyrene is rarely recycled becauseit is usually not cost effective.
2. Although different schemes have been put into place, it is difficult to separate products, i.e. drinksbottles, as the bottle and closures are made of different polymers.
3. Recycling may be the answer to this problem, as thermoplastics can be moulded into different things,although the main problems are sorting and collection.
4. Then there’s the problem with disposal, polymers are durable and degrade very slowly, which is a problem for landfill sites. Incineration may not be the answer either, as in some cases burning polymers can release toxic fumes.
5. Oil is the raw material of synthetic polymers, and is not an infinite resource but consumes a lot of energy in the production process and produces pollution. The manufacture of blow moulding for example, also uses a lot of energy.
6. There is ongoing environmental concerns of how sustainable polymers are.

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