Plastics

Plastics (the word comes from the Latin plasticus and Greek plastikos meaning 'able to be moulded') are man made polymers. A polymer is a chain of lots of identical molecules - called monomers - joined together. Traditionally most plastics are made from monomers produced from oil although bioplastics made with alternative naturally produced monomers are becoming more common.


There are 2 types:

1. Thermoplastics: are shaped by heat and can be reshaped by applying heat (melting). This means that they can be recycled. They consist of lots of long polymer chains with no links between them that can slide past each other and are only held together by weak attraction between the chains. Examples are polyethylene, polypropylene, polyvinyl chloride, polystyrene and polyamides.

2. Thermoset plastics: are shaped by heat and a second process occurs where the polymer chains are linked together (called crosslinking). This means the polymer chains are fixed in position and cannot move even when heated. Resulting in plastics that do not melt. This means that they cannot be recycled. Examples include silicone and polyurethane.


There are 7 groups that plastics are divided into for recycling:

  1. PETE (Polyethylene Terephthalate) - Easy to recycle. Used for fizzy drink bottles, water bottles and many common food packages.
  2. HDPE (High density Polyethylene) - Easy to recycle. Used for packaging detergents, bleach, milk containers, hair care products and motor oil.
  3. PVC (Polyvinyl Chloride) - Difficult to recycle. Widely used for pipes, packaging etc.
  4. LDPE (Low-density Polyethylene) - Ued for many different kinds of wrapping, grocery bags and sandwich bags.
  5. PP (Polypropylene) - Used for clothing, bottles, tubs and ropes.
  6. PS (Polystyrene) - Used for cups, foam food trays and packing.
  7. Other Could be a mixture of any and all of the above or plastics not readily recyclable such as polyurethane. Hard or impossible to recycle.


Most things made of plastic have a symbol embossed on them showing which group they belong to like this: