A Practical Guide to Identifying ABS and PS Plastics

  Distinguishing between ABS (Acrylonitrile Butadiene Styrene) and PS (Polystyrene) is a common need in the plastics industry. Several methods, from simple to more observational, can be employed. A definitive new method involves using ethyl acetate as a solvent; when wiped, ABS will not show silking, whereas HIPS (High-Impact Polystyrene) will form silky strands, though this test is most reliable for pure materials. Common identification methods rely on visual and physical properties. ABS typically has a superior surface brightness and significantly better toughness than PS. When set on fire, ABS burns with a yellow flame without dripping and leaves a surface with densely packed small holes, emitting a faint, sweet smell. PS, on the other hand, has several types: the crisp and transparent GPPS, the tougher HIPS, and the foam-grade EPS. HIPS has average brightness and lower toughness compared to ABS. It burns with an orange-yellow, sparkling flame, producing dense black smoke and a distinct styrene smell, and the surface remains bright after the fire. A key visual differentiator is that the cut surface of HIPS appears whitish, which GPPS does not. In specific applications like TV housings, which use both ABS and HIPS, identification is often based on these surface and physical characteristics. A surface with higher brightness is usually ABS. Furthermore, when attempting to break with pliers, ABS demonstrates higher hardness and requires more force, after which one can further distinguish by the flame and smell.