Polystyrene

Polystyrene is a synthetic polymer made from the monomer styrene, a liquid hydrocarbon derived from petroleum. It consists of long chains of styrene units and can be produced in a variety of physical forms that suit different applications.

Polystyrene exists mainly as solid plastic and as foams. General-purpose polystyrene (GPPS) is a clear, rigid, brittle thermoplastic. High-impact polystyrene (HIPS) is GPPS that contains rubber (usually polybutadiene) to improve toughness. Foam polystyrene includes expanded polystyrene (EPS), used for lightweight packaging and insulation, and extruded polystyrene (XPS), used for rigid insulation boards. Properties vary: GPPS is transparent and stiff, HIPS offers better impact resistance, and EPS/XPS provide low density and good thermal insulation. Polystyrene generally has a moderate glass transition temperature and limited heat resistance, and is relatively resistant to many chemicals but can be attacked by some solvents.

Production involves free radical polymerization of the styrene monomer. Methods include suspension, emulsion, and bulk polymerization, often with initiators and stabilizers. The result is long polystyrene chains that can be processed by extrusion, injection molding, blow molding, and thermoforming.

Uses span consumer packaging, food service items, and household goods (AM/FM radio housings,CD cases), as well as insulation and protective packaging. EPS is common for packaging peanuts and cold-chain insulation; XPS is used for building insulation; HIPS is used for rigid consumer parts.

Environmental aspects include persistence in the environment and challenges in recycling. Polystyrene can be mechanically or chemically recycled, but many EPS products are not widely recycled. Incineration can release styrene and other pollutants, raising regulatory and waste-management considerations in many jurisdictions. Polystyrene was first reported in 1839 and later developed into commercially produced plastics in the 20th century.