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We use plastics in nearly everything we do, often without realising it. At home, clothes, carpets, baths and brushes are often made of plastics. So too are parts of fridges and freezers, vacuum cleaners and washing machines. Modern houses have plastic guttering and downpipes; the connections to water and gas mains are made of plastic piping. Electrical wiring is insulated with a plastic covering.
Heart valves and false teeth are made of plastics. So are records and video tapes, compact discs and camera film. More than a thousand plastic parts are built into the average European car.
Where do plastics come from?
The first plastic, celluloid, was made from coal and was used in the manufacture of billiard balls to avoid using ivory from elephants' tusks. Nowadays, only table tennis balls are made from celluloid.
Only 4% of the oil consumed in this country is used to make plastics and less than half of this is used to make plastics for packaging Plastics for packaging.
Plastics for packaging
Packaging plastics are produced in chemical factories and have rather long names. The six major ones are:
- LDPE: low density polyethylene
- HDPE: high density polyethylene
- PP: polypropylene
- PVC: polyvinylchloride
- PSE: polystyrene
- PET: polyester (polyethylene terephthalate: try saying that if you are not a chemist!)
Luckily, they are usually known by their initials
The plastics raw materials (called polymers) usually come in granule or powder form. They are then converted using heat and pressure on special processing machinery to produce bottles, tubs, films, crates, etc.
Thirty years ago plastic bottles used to look cloudy and we could easily distinguish them from glass bottles. But scientists have now learnt how to stretch plastics in a special way to make them clearer and tougher. PET bottles for fizzy drinks are made in this way. Films too can be stretched (in a different way) and, for example, another plastic, nylon, is used for boil-in-bag foods such as frozen fish (their sharp bones might puncture other films). Stretched PET film is used as oven roasting bags for cooking chickens at oven temperatures up to 200°C.
More information about processing plastics is available from The British Plastics Federation.