ASA — Acrylonitrile Styrene Acrylate
Acrylonitrile Styrene Acrylate
ASA (acrylonitrile styrene acrylate) is an amorphous styrenic thermoplastic similar to ABS but with excellent UV and weathering resistance. It is the reference for aesthetic technical parts intended for outdoor use (mirror housings, gutters, garden furniture).
- Mold temperature: 50-80°C
- Melt temperature: 230-260°C
- Shrinkage: 0.4-0.7%
- Density: 1.06-1.08
- Manufacturer grades: Luran S 757R (INEOS Styrolution), Geloy ASA (SABIC)
Processing
ASA is hygroscopic: light drying of about 2 to 4 h at 80 °C before molding is recommended, otherwise residual moisture causes silver streaks. Run the melt between 230 and 260 °C with a mold regulated between 50 and 80 °C for good surface gloss and low shrinkage (0.4 to 0.7 %).
Advantages
- Excellent UV and weathering resistance: outdoor applications
- Good rigidity-to-impact-resistance balance (similar to ABS)
- Excellent surface finish, paintable and bondable
- Good dimensional stability (amorphous, low shrinkage)
Limitations
- Hygroscopic: light drying required before molding
- Limited chemical resistance to solvents and hydrocarbons
- Moderate continuous service temperature
- Higher cost than ABS for indoor applications
Common injection molding defects
- Weld lines — Very visible on dark colors: raise melt temperature and speed
- Silver streaks — Residual moisture: dry ASA at 80 °C before molding
- Sink marks — On thick sections: increase holding and review rib design
Typical applications
Exterior automotive parts, outdoor electrical housings