There are hundreds of types of industrially produced plastics, of which more than 60 are commonly used. The common classification method is as follows: According to the performance after heating. 1. Thermosetting plastic. The characteristic of this type of plastic is that it is cured and formed after a certain time of heating or adding a curing agent at a certain temperature. The cured plastic is hard in texture and insoluble in any solvent, and it cannot be softened again by heating. It will decompose if the heating temperature is too high. Common thermosetting plastics include bakelite, electric jade, decorative panels and unsaturated polyester plastics. 2. Thermoplastic. The characteristics of this kind of plastics are softened by heat and hardened by cooling. Generally, there are only physical changes during processing to maintain their chemical nature. Most of the resins of this type of plastic are made by addition polymerization. Common thermoplastics are: nitrocellulose plastics, cellulose acetate plastics, polyethylene plastics, polypropylene plastics, polystyrene plastics, polyvinyl chloride plastics and so on. For example, our common mineral water bottles, plastic bags, etc. According to the scope of application. 1. General-purpose plastic. This type of plastic mainly refers to a type of plastic with large output, wide use and low price. They account for about 80% of total plastic production. The main varieties are: polyethylene, polyvinyl chloride, polypropylene, polystyrene, phenolic and amino plastics, etc. 2. Engineering plastics. Generally refers to plastics that can be used as structural materials in engineering technology. The remarkable feature of this type of plastic is high mechanical strength, chemical corrosion resistance and high temperature resistance, which can replace metal or be used for other special purposes. The main varieties are: polyamide, polycarbonate, polyoxymethylene, polysulfone, ABS, polyphenylene ether, fluoroplastics, etc. Divided by the degree of flammability. 1. Flammable plastic. This type of plastic burns violently after encountering an open flame and is not easy to extinguish. Such as nitrocellulose plastics, which are classified as dangerous goods. 2. Flammable plastic. This kind of plastic burns in an open flame and has no self-extinguishing property, but the burning speed is relatively fast. Such as polyethylene, polypropylene, etc. 3. Flame-retardant plastic. This type of plastic can burn in a strong open flame, and will extinguish soon after leaving the fire. Such as phenolic plastic, cellulose acetate plastic, polyvinyl chloride plastic and so on