Polystyrene

Polystyrene (PS) ( /ˌpɒliˈstaɪriːn/) is an aromatic polymer made from the monomer styrene, a liquid petrochemical. Polystyrene is one of the most widely used plastics, the scale of its production being several billion kilograms per year. It is a colorless solid that is used, for example, in disposable cutlery, plastic models, CD and DVD cases, and smoke detector housings. Products made from foamed polystyrene are ubiquitous, for example packing materials, insulation, and foam drink cups. Its very slow biodegradation is a focus of controversy, and it is often abundant as a form of litter in the outdoor environment, particularly along shores and waterways especially in its low density cellular form.

As a thermoplastic polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100 °C, its glass transition temperature. It becomes rigid again when cooled. This temperature behavior is exploited for molding and extrusion, since it can be cast into molds with fine detail. Polystyrene can be transparent, white, or, upon dying, various colors.