Polystyrene is made from the monomer styrene, which is a liquid petrochemical.
The three most important grades of styrene are:
- GPPS: General-purpose polystyrene, also known as crystal-clear polystyrene, is a fully transparent, rigid and rather brittle low cost thermoplastic made from styrene monomer. GPPS is a solid product manufactured in the form of 2-5 mm pellets.
- HIPS: High impact polystyrene contains usually 5 to 10% rubber (butadiene) and is used for parts, which require high(er) impact resistance. HIPS is a graft copolymer having polystyrene sidearm. The grafting occurs when some of the radicals react with the double bonds of the polybutadiene.
- EPS: Expandable polystyrene consists of micro-pellets or beads containing a blowing agent (usually pentane). The expanded or foamed polystyrene is thermally insulating and has high impact resistance.
Uses include protective packaging (such as packing peanuts and CD and DVD cases), containers, lids, bottles, trays, tumblers, disposable cutlery and in the making of models.