General - purpose polystyrene
Polystyrene, sometimes abbreviated PS, is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. Polystyrene is one of the most widely used kinds of plastic.
Polystyrene is a thermoplastic substance, which is in solid (glassy) state at room temperature, but flows if heated above its glass transition temperature (for molding or extrusion), and becoming solid again when cooling off. Pure solid polystyrene is a colorless, hard plastic with limited flexibility. It can be cast into molds with fine detail. Polystyrene can be transparent or can be made to take on various colors.
Solid polystyrene is used, for example, in disposable cutlery, plastic models, CD and DVD cases, and smoke detector housings. Products made from foamed polystyrene are nearly ubiquitous, for example packing materials, insulation, and foam drink cups.
Polystyrene can be recycled, and has the number "6" as its recycling symbol. Unrecycled polystyrene, which does not biodegrade, is often abundant in the outdoor environment, particularly along shores and waterways, and is a form of pollution.
Polystyrene is commonly produced in three forms: extruded polystyrene, expanded polystyrene foam, and extruded polystyrene foam, each with a variety of applications. Polystyrene copolymers are also produced; these contain one or more other monomers in addition to styrene. In recent years the expanded polystyrene composites with cellulose and starch have also been produced.
Extruded polystyrene foam insulation is sold under the trademark Styrofoam by Dow Chemical. This term is often used informally for other foamed polystyrene products.