General purpose polystyrene (GPPS)

1 General description

GPPS is a hard, transparent material with a high gloss. It is most commonly described as general purpose (GP) polystyrene but terms such as standard polystyrene, normal polystyrene, clear polystyrene, or styrene homopolymer are also in use. In this section, the definition polystyrene (PS) moulding material is used according to ISO 1622-2. Below 100 °C PS moulding materials solidify to give a glasslike material with adequate mechanical strength, good dielectric properties, and resistance towards a large number of chemicals for many areas of application. Above its softening point, clear polystyrene softens and allows the resin to be readily processed by common industrial techniques such as injection moulding or extrusion. PS moulding material may contain small quantities of lubricants (internally or externally) to help process the resin for end usage. The addition of antistatic agents, UV stabilisers, glass fibres, or colourants via compounding is also common. GPPS offers excellent transparency, mouldability and heat stability with low specific gravity – which allows the injection moulding or extruding of very economic specimens. There are varieties of grades available with a wide range of choices to match the needs of the consumers. The main application areas are disposable cups, small containers, disposable kitchen utensils, cosmetic cases, dust covers for electronic equipment, coatings for gloss papers, refrigeration trays, CD and jewel boxes, medical pipettes, petri dishes and meat trays.

2 Flow diagram of GPPS production