StyrenAcrylonitrilKopolymer

Styrene–acrylonitrile copolymer (SAN) is an amorphous thermoplastic produced by randomly copolymerizing styrene with acrylonitrile. Typical SAN formulations contain approximately 20–40% acrylonitrile by weight, with the balance being styrene. The copolymer delivers greater rigidity, chemical resistance and heat tolerance than polystyrene, while maintaining high clarity.

SAN is transparent and has a glass transition temperature around 105–110 °C, giving improved heat resistance for molded parts. It features good surface hardness and dimensional stability and good resistance to many acids and solvents. Its impact strength is moderate, and weathering resistance can be limited unless stabilizers are used. SAN is processable by common thermoplastic methods such as injection molding, extrusion or thermoforming, and can be blended with other polymers, notably polycarbonate to form PC/SAN blends that improve impact resistance.

Applications for SAN include electrical housings, appliance components, display and packaging items, kitchenware, and other clear parts requiring rigidity and chemical resistance. It is often chosen as an economical alternative to more expensive clear resins while not matching the toughness of polycarbonate.

Production of SAN is accomplished by free-radical polymerization of styrene and acrylonitrile in bulk, suspension or emulsion processes. Grades vary in acrylonitrile content, molecular weight and additives such as stabilizers, UV absorbers and pigments to tailor transparency and weatherability.