Styreneacrylonitrile

Styreneacrylonitrile (SAN) is a thermoplastic copolymer of styrene and acrylonitrile. It is produced by free-radical copolymerization to yield a random distribution of styrene and acrylonitrile units and is used for clear, rigid plastic parts.

Typical SAN compositions feature roughly 60–70% styrene and 30–40% acrylonitrile by weight; the acrylonitrile increases the glass transition temperature and chemical resistance, while styrene provides processability and stiffness. SAN is more transparent and heat resistant than polystyrene, but less impact resistant. The nitrile content also contributes to improved dimensional stability and solvent resistance relative to high-styrene resins.

Processing and properties: As a thermoplastic, SAN can be processed by injection molding, extrusion, blow molding, and thermoforming. It is often used on its own for clear housings or as a matrix modifier with other polymers; however, its relatively low toughness leads to brittleness, and many grades are formulated or blended to improve impact resistance. SAN typically remains clear or translucent, though higher acrylonitrile content can reduce optical clarity somewhat. UV exposure can cause yellowing over time, unless stabilized grades are used.

Applications: SAN is used in consumer electronics housings, appliance components, protective covers, and other applications requiring clarity, rigidity, and chemical resistance. It is less common for structural parts where high impact strength is essential, and may be selected for aesthetic and optical requirements.

Recycling and safety: SAN resins are recyclable with other styrenic plastics and are generally regarded as safe for industrial use. Some grades may be certified for food contact, depending on additives and processing.