Polystyrene (PS) is one of the most widely used plastics at several billion kilograms per year. Polystyrene can either be a thermoplastic or a thermoset. A thermoplastic polystyrene is in a solid (glassy) state at room temperature but flows if heated above its transition temperature of about 100ºC, becoming solid again once cooled. Absolute solid polystyrene is a colorless, hard plastic with partial flexibility. Polystyrene molds with excellent detail and can be manufactured as transparent or to take on a variety of colors.
Solid polystyrene is used typically used in the manufacturing of disposable cutlery, plastic models, CD and DVD cases, and smoke detector housings. Products made from foamed polystyrene are nearly ubiquitous with insulation, foam drink cups, and packing materials.