1. Density method: examine the density of various plastics, use liquid as the medium, check the ups and downs of the plastic in the liquid medium, and roughly distinguish the major types of plastics, such as a piece of plastic in water, floating on the surface of the water, it can be concluded that the raw material is not PVC (due to the density of PVC>1).

2. Combustion method: mainly examines the color of the flame and the smell and smoke emitted during combustion. Generally speaking, the burning flame of polyolefin materials is mostly blue or light blue, the smell is relatively gentle and light, and the smoke is white. Most raw materials with benzene or chlorine will easily emit black smoke after burning, and the smell will be strong. In addition, such as PE and PP have dripping burning phenomenon, while PVC etc. have no dripping burning, but have self-extinguishing phenomenon.

3. Optical method: It mainly examines the transparency of raw materials. Commonly used transparent raw materials are: PS, PC, PMMA, AS; translucent raw materials are: PE, random copolymer PP, homopolymer PP, soft PVC, transparent ABS, etc. The other raw materials are basically opaque.

4. Color discrimination method: Generally speaking, raw materials without additives, if they contain double bonds, the color will be slightly yellow, such as ABS, because of the copolymerization of butadiene, the polymer still contains double bonds after polymerization. So it will be slightly yellow.

Most of the other identification methods rely on various instruments, such as infrared spectroscopy, mass spectrometry, nuclear magnetic resonance, differential thermal scanning, thermal analysis, etc.