Polyethylene (PE) is a thermoplastic resin made by polymerizing ethylene. In industry, it also includes copolymers of ethylene and a small amount of α-olefins. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum use temperature can reach -100 ~ -70 ° C), good chemical stability, can withstand most acids and alkalis (not resistant to oxidation Nature acid). Insoluble in common solvents at room temperature, low water absorption, excellent electrical insulation
Polyethylene can be processed using general thermoplastic molding methods (see Plastic Processing). Very versatile, mainly used to manufacture films, packaging materials, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulation materials for TV, radar, etc.
Polyethylene is divided into high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE) according to the polymerization method, molecular weight and chain structure.
LDPE: Properties: odorless, odorless, non-toxic, matte surface, milky white waxy particles, density about 0.920 g / cm3, melting point 130 ℃ ～ 145 ℃. Insoluble in water, slightly soluble in hydrocarbons, toluene, etc. It is resistant to the erosion of most acids and alkalis, has low water absorption, can maintain flexibility at low temperatures, and has high electrical insulation. Processing methods such as injection molding, extrusion molding, and blow molding can be used. Mainly used as agricultural film, industrial packaging film, pharmaceutical and food packaging film, mechanical parts, daily necessities, building materials, wire, cable insulation, coating and synthetic paper, etc.
LLDPE: Properties: Because the molecular structure of LLDPE and LDPE are obviously different, the performance is also different. Compared with LDPE, LLDPE has excellent environmental stress cracking resistance and electrical insulation, high heat resistance, impact resistance and puncture resistance. Production process: LLDPE resin is mainly produced by full-density polyethylene equipment. The representative production processes are Innovene process and UCC Unipol process. 
Uses: Through the injection molding, extrusion, blow molding and other molding methods, production of films, daily necessities, pipes, wires and cables, etc.
HDPE: Properties: natural, cylindrical or oblate particles, the particles are smooth and clean, the size of the particles should be 2 mm to 5 mm in any direction, no mechanical impurities, and thermoplastic. The powder is a white powder, and qualified products are allowed to be slightly yellow. It is insoluble in common solvents at room temperature, but it can swell in aliphatic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons for prolonged contact. It is slightly soluble in toluene and acetic acid above 70 ℃. Oxidation occurs when heated in the air and under the influence of sunlight. Resistant to most acids and alkalis. Low water absorption, can maintain flexibility at low temperature, high electrical insulation.
Uses: use injection molding, blow molding, extrusion, rotomolding and other molding methods to produce film products, daily necessities and industrial various sizes of hollow containers, pipes, packaging calendering belts and ligatures, ropes, fish nets and braiding Fiber, wire and cable, etc.
High-pressure polyethylene: more than half of it is used in film products, followed by pipes, injection molded products, wire wrapping, etc.
Medium and low pressure polyethylene: mainly injection molded products and hollow products. 
Ultra-high pressure polyethylene: due to its excellent comprehensive properties, it can be used as an engineering plastic