Polymer materials and their structures
Plastics are polymer materials shaped into useful articles, usually with carefully selected additives. An additive may change flexibility, colour, resistance to light, fire behaviour or processing, but it does not turn every polymer into the same material. Common examples include poly(ethene) (PE), poly(propene) (PP), poly(chloroethene) (PVC) and poly(ethylene terephthalate) (PET). Their different repeat units and chain arrangements give different properties.