The burning test and the density float test are the two most effective methods for differentiating automotive exterior plastics. Using them together can quickly and accurately identify common material types.
1. Burning Test: Precisely Identifying Chemical Properties By observing the flame color, smoke, odor, and melting behavior during combustion, different plastics can be effectively distinguished:
PP (Polypropylene): Yellow flame at the top and blue at the bottom, with a paraffin-like smell, obvious dripping after melting, similar to burning candle.
ABS: Yellow flame with black smoke, emitting a pungent styrene smell (similar to burning rubber), dripping slowly.
PC (Polycarbonate): Yellow flame, lots of black smoke, with a fruity odor, melts but does not drip.
ASA: Yellow flame, black smoke, odor similar to ABS but milder, does not drip easily.
It is recommended to only test with small samples of scrap material in a well-ventilated environment to avoid inhaling harmful gases.
2. Density Float Test: A Simple and Efficient Physical Method
PP: Density approximately 0.9 g/cm³, floats on water, making it one of the few engineering plastics capable of floating.
ABS, PC, ASA, TPO: Densities are all greater than 1, sink in water, and can be quickly distinguished from PP.
3. Comprehensive Judgment is More Reliable
A single method may carry the risk of misjudgment. It is recommended to combine appearance, gloss, tactile elasticity, and sound when tapped as auxiliary indicators:
PP feels soft and elastic, and produces a dull sound when tapped;
ABS is hard, has a high gloss, and produces a crisp sound when tapped;
PC is highly transparent, has strong impact resistance, and is not easily scratched.
