Term applied to many natural and synthetic materials with different forms, properties and appearances. They are all composed of large, usually carbon-based, molecules called polymers. The chemical composition of the polymers and the size and arrangement of their molecules determine the key properties of the plastic material. In addition to the base polymer most plastics have substances added to give colour, improve performance and facilitate manufacture.
See also Conservation of plastics
Most commercially useful plastics are derived from oil, natural gas and coal; they are referred to as synthetic polymers. Natural polymers that have been used as plastics include gutta-percha, horn, beeswax, tortoiseshell and shellac. These and later synthesized polymers share the potential to be shaped into new forms as solids, fibres or coatings. Natural and synthetic rubbers are organic polymers called elastomers but they are normally grouped apart from plastics. Some semi-synthetic polymers are made by treating a natural material, such as cotton (almost pure cellulose), with chemicals to produce a modified plastic substance. ...