ABSTRACT
Plastics have low thermal conductivity and thermal capacity, but thermal movement is high. Two distinct types of plastics can be distinguished: thermoplastics and thermosetting plastics. The properties relevant to the main building uses of the following thermoplastics are now considered: Polyethylene, often called polythene, is one of the polyolefin group. Thermoplastics are also precluded from such use by their tendency to creep under sustained loading coupled with a serious loss of strength at elevated temperatures. Like paints, rubbers and sealants, plastics consist of molecules joined together to form chain molecules, or polymers which are normally randomly coiled. Rubber is useful as anti-vibration mountings for machinery and as a floor covering or underlay to absorb impact noise. Recently developed ethylene-propylene rubbers have extremely good resistance to ozone and to ageing, and look promising for use as roof coverings. Rubbers are similar to thermosetting plastics but differ in the ease with which the molecular chains are able to uncoil.
