Styrene Acrylonitrile Copolymer (SAN) is a copolymer of styrene and acrylonitrile. SAN consists of approx. 70% styrene and 30% acrylonitrile. It is widely used and is processed instead of polystyrene due to its greater thermal resistance. SAN is similar to polystyrene. Like polystyrene, it is optically transparent and brittle in mechanical behavior.