Plastics are materials made from long molecules (Polymers). Generally Plastics contain numerous chemical additives to refine their mechanical properties. Plastics are widely used throughout industry. Plastics are widely used because they can be formed using mass production methods into complicated shapes at a very low cost. The range of properties available from plastics materials has made them the prime choice for many aplications. Plastics are light, and durable. They generally are not able to withstand high temperatures and they are not as strong as metals.

When thermoplastics are heated they become softer and less stiff until they become viscous liquids. On cooling the original properties return.

Thermosetting moulding powders will also soften on heating allow them to be formed into shapes. In this process the adjacent polymers form chemical cross links. This results in the material which is hard, rigid, insoluble and infusible. The thermoset cannot be easily reprocessed. Typical thermosetting materials include phenolics, ureas, melamine, epoxides and polyesters. Some thermosetting resins when mixed with long glass fibres are called Glass Reinforced Plastics.

A rubber/elastomer is a polymeric material with long flexible molecular chains an the ability to deform elastically when vulcanised. During the vulcanising process, rubber molecules are linked with adjacent molecules at intervals along their lengths, usually by sulphur to form a cross-linked elastic material which is stable over a wide range of temperatures.