ABS and ASA are two common styrenic engineering plastics. They look and process very similarly, so knowing the difference matters, especially for outdoor applications.
The structural difference
ABS consists of acrylonitrile, butadiene and styrene. The butadiene rubber phase that provides impact strength tends to degrade over time under sunlight and oxygen. In ASA this phase is replaced with acrylate rubber, which makes the material far more stable against UV and weathering.
Which one for which application?
- ABS: Electronic housings, interior automotive parts, appliances, toys and 3D printing filament. It has good surface quality and can be painted and plated.
- ASA: Exterior profiles, mirror housings, garden and outdoor products, satellite dishes and other parts exposed to constant sunlight. Color fading and yellowing develop much more slowly.
Cost balance
ASA is generally more expensive than ABS. If the part is used indoors, ABS is often sufficient and economical. If the part must keep its appearance outdoors for many years, the extra cost of ASA pays for itself.
UV-stabilized ABS grades exist for outdoor use as an alternative, but where long-term color and surface stability is required, ASA remains the first choice.