Appearance identification method
（1） PE, PP, PA, etc. have different bendability. The hand touch has a hard wax like smoothness, and there is soft horny sound when tapping. In comparison, PS, ABS, PC, PMMA, etc., have no extensibility, and the hand touch is rigid and sexy, and the sound is clear and crisp when knocking.
（2） The relative density of PE and PP is less than 1, so they float in water; most other plastics are greater than 1, so they sink in water.
（3） Before dyeing, LDPE plastic particles are milky white, transparent, soft, soft and tough, slightly elongated, easy to bite and deform with teeth. HDPE is milky white, opaque, slightly hard in texture, and can be deformed by teeth. PP is white and translucent, higher than PE transparency and lighter, more rigid, extremely difficult to deform with teeth.
（4） The main difference between PS, hips and ABS is that PS is brittle, hips and ABS are ductile, so PS is easy to brittle fracture during bending. The latter two are hard to break and turn white in the bending part. PS is transparent, hips is milky white, ABS is light tooth color.
Combustion observation method
Different materials have different combustion behaviors during combustion, such as flame color and smell (in the actual processing process, plastics will degrade due to heat, and there will be low molecular flavor), which is also the basic method to identify common materials.
The burning condition of the smoke is different from that of the flame
PE is inflammable, with yellow top and blue bottom, and little smell of falling stone and wax
PP is inflammable and continuous burning, with yellow on the top and blue at the bottom with less oil smell
PS is inflammable and continuous burning, with yellow upper and lower blue, more smoke without dripping and foaming styrene smell
ABS flammable continuous burning all yellow smoke coking rubber smell
Hips is inflammable, continuous burning, full yellow smoke without dripping and foaming rubber smell
PMMA has light blue top, white top and foamy flowers and fruits under continuous combustion of PMMA
PA is inflammable, continuous burning, little drop burning hair smell
POM can burn continuously without any pungent taste
Pet is inflammable, with little vinegar smell
PC slow burning non continuous burning yellow and black smoke carbon beam foaming flower and fruit odor