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Polyvinylchloride (PVC) PDF Print E-mail

This is one of the most versatile and widely used of all plastics. Its uses range from hard panels to cling film, from garbage cans to electrical insulation. It can be shaped by injection moulding, blowing, heat welding and film drawing and can be used clear or coloured.

PVC is made from vinyl chloride monomer which is highly toxic and a known human carcinogen.

Health effects
When the monomer is polymerised to form the plastic it is no longer toxic, but a very small amount of the monomer remains in the product. PVC intended for use with food is made to very stringent specifications and, in Australia, must not contain more than five ppm of vinyl chloride monomer. It is important that only 'food-grade' PVC be used with food as ordinary PVC may contain much more of the toxic monomer. This can diffuse out of the plastic into the food, particularly if the food is oily or strongly acid or alkaline. For example, do not use garbage cans for making fruit drinks or pickled cabbage, or for storing edible oil.

The plastic is made flexible by adding plasticisers, and commercial cling film may contain up to 40 per cent by weight of this. The plasticisers are non-volatile esters and may diffuse into such foods as cheese and meat.

Environmental effects
Because of its extraordinary stability, PVC is difficult to dispose of. It is not biodegradable and unlike polyethylene and many other plastics it is only very slowly decomposed by exposure to the sun.

When PVC is burned it gives off hydrochloric acid and some of the chlorine combines with other material to form very toxic and stable organochlorine compounds such as dioxins. See also Introduction (Persistent Organic Pollutants).

In some countries the use of building materials containing PVC is prohibited, mainly because of the very toxic fumes which are formed when there is a fire. In Australia, some local councils are promoting the use of alternatives to PVC pipe, such as aluminium and clay.

It is possible to recycle PVC by melting and remoulding it, but there is little recycling of PVC in Australia; the recycling code number for PVC is 3. (See Plastics.)

For food containers, polyethylene, polypropylene or PET are to be preferred. They are usually clear, white or milky in appearance. (See Plastics.)

There are many different plastics for other purposes but often they are more expensive and not as easy to shape as PVC. It would be desirable not to use PVC for making throwaway articles and packaging, and to recycle it more successfully.

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