Polystyrene (-[CH2CH(C6H5)]n-) belongs to a polymer group called polyolefins, and is obtained by polymerization of styrene usually derived from catalytic process of dehydrogeneration of ethylbenzene (approx. 85% of global production), or from the Halcon Oxirane process (approx. 15% of global production) or refining of petroleum.
Mixed with some additives, polystyrene provides a basis for many plastics designated with letters (PS). Pure polystyrene is a colourless, hard, brittle thermoplastic (a material formed by melting), with a very limited flexibility. Currently, several varieties of basic styrene materials are manufactured, including:
a) polystyrene – homopolymer, without any modifications, also called low-impact (LIPS) or general-purpose (GPPS) polystyrene,
b) polystyrene modified with butadiene (CH2=CH-CH=CH2), called high-impact polystyrene – HIPS,
c) copolymer of styrene (H5C6-CH=CH2) with acrylonitrile (CH2=CH-CN) – SAN,
d) copolymer of acrylonitrile, butadiene and styrene – ABS.
As a plastic, polystyrene can be colourless, dimly transparent, or coloured with any bright colours. Compared to polyethylene and polypropylene, its advantage is a lower softening temperature and lower viscosity of the melt, which makes it easier to obtain small objects with fine detail by injection moulding.
Polystyrene, as a solid material, is used for the manufacture of costume jewellery, toothbrushes, CD boxes, toy parts. However, it has a significantly lower chemical resistance than polyethylene and is rather not used for the manufacture of packaging for food products.