Generally, plastics are divided into three types: general plastics, engineering plastics and special plastics. There are five types of general plastics, namely polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and acrylonitrile-butadiene styrene copolypolymer (ABS). Engineering plastics generally refer to the ability to withstand a certain external force, Special plastics with good mechanical properties and high and low temperature resistance, good dimensional stability, can be used as engineering structures. Special plastics generally refer to the plastics with special functions, which can be used in aviation, aerospace and other special application fields, such as fluorine plastics, silicone, foam plastics, according to the different physical and chemical properties of various plastics. Plastics can be divided into two types: thermosetting and thermoplastic. (1) Thermoplastic: refers to the plastic that will melt after heating, can flow to the mold for cooling and forming, and will melt again after heating (2) Thermosetting plastic Thermosetting plastic refers to the plastic that can cure or has insoluble (melting) characteristics under heat or other conditions, such as phenolic plastic, epoxy plastic, etc