Polystyrene is one of the most important commodity plastics. The production volume of polystyrene and styrene copolymers is several million tons per year. It is sold under various trade names, including Styrofoam™, Styropor®, and Styron™
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 sidearms. 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, has high impact resistance and good processability.