Plastics can be divided into two categories according to their own properties: thermosetting plastics which can be processed repeatedly and can basically maintain their properties and thermosetting plastics which can only be molded once. According to their use, they can be divided into general plastics, which are widely used, cheap and have better comprehensive properties, such as PEPP-PVCPS, and Amine plastics, which have good physical and mechanical strength, and may replace engineering plastics such as: ABS, nylon, which are used in construction machinery by metals. Polyester POMN TPX-1 et al. And a class of engineering plastics having particular properties, such as Not good radiation resistance, high temperature resistance and other special plastics, such as: polyaryl sulfone, liquid crystal polymer, etc. Thermoplastic plastics can be divided into amorphous polymers and crystallized polymers according to the molecular crystallization size of thermoplastic resins.