Polystyrenes comprise one of the largest and most widely used families of plastics. Often called the workhorse of the thermoplastics, polystyrenes consist of the basic general-purpose materials, plus a wide variety of modified grades of polymers, copolymers, and blends. All polystyrenes generally have several features in common: (1) low cost, (2) unexcelled electrical insulating properties, (3) virtually unlimited colorability, (4) ability to be made crystal clear (in general-purpose grades), and (5) high hardness and gloss. Polystyrenes have excellent molding and extrusion characteristics, and are formed readily and inexpensively by any of the thermoplastic forming methods. Types available include molding and extrusion grades, foams, sheet and film, and fiber. A thermoplastic resin used for molding, in lacquers, and for coatings. In the form of vinyl toluene, which consists of mixed isomers of methyl styrene, the material is reacted with drying oils to form alkyd resins for paints and coatings. So-called general-purpose polystyrenes are characterized by clarity, luster, colorability, rigidity, unexcelled dielectric properties, and moldability. They are used where rigidity and appearance are important, but where toughness is not required. Typical uses include wall tile, container lids, and brush backs. foamed Polystyrene were used in many forms, including extruded sheet (which is then thermoformed, e.g., egg cartons, trays); expandable polystyrene (EPS) beads, which contain a blow agent (usually pentane), and which are processed into low-density foamed products, such as hot and cold drink cups and protective packaging; and block and heavy sheet, used for thermal insulation.
