SAN — Styrene Acrylonitrile
Styrene Acrylonitrile
SAN (styrene-acrylonitrile) is a transparent amorphous thermoplastic, more rigid than PS and with better chemical and thermal resistance. Widely used in injection molding for transparent technical parts (housewares, cosmetics, optical parts).
- Mold temperature: 40-70°C
- Melt temperature: 220-260°C
- Shrinkage: 0.3-0.7%
- Density: 1.07-1.08
- Manufacturer grades: Luran 358N (INEOS Styrolution), Starex SAN-S (Samsung SDI)
Processing
SAN is slightly hygroscopic: light drying of about 2 to 3 h at 70-80 °C before molding is recommended to avoid silver streaks. Run the melt between 220 and 260 °C with a mold regulated between 40 and 70 °C; its low amorphous shrinkage (0.3 to 0.7 %) ensures good dimensional stability.
Advantages
- High transparency and good surface finish
- More rigid than PS and better thermal resistance
- Good chemical resistance (greases, oils, alcohols)
- Good dimensional stability (amorphous, low shrinkage)
Limitations
- Remains brittle: limited impact resistance (prefer ABS)
- Slightly hygroscopic: light drying recommended before molding
- UV-sensitive without stabilizer
- Limited chemical resistance to chlorinated solvents and ketones
Common injection molding defects
- Weld lines — Very visible in transparency: raise melt temperature and injection speed
- Silver streaks — Residual moisture: lightly dry SAN at 70-80 °C before molding
- Jetting — Filling too fast at the gate: reduce initial speed and reposition the gate
Typical applications
Cosmetics, transparent household items, dashboards