The main raw material for foreign production is polyethylene (PE), and the domestic production is mainly polypropylene (PP), which is a thermoplastic resin produced 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 -70 ～ -100 ℃), good chemical stability, can withstand most acids and alkalis (not resistant to oxidation Acid), insoluble in common solvents at room temperature, low water absorption, excellent electrical insulation; but polyethylene is very sensitive to environmental stress (chemical and mechanical effects), poor heat resistance and aging. The properties of polyethylene vary from species to species, depending on the molecular structure and density. Different production methods can be used to obtain products with different densities (0.91 ～ 0.96g / cm3). Polyethylene can be processed using general thermoplastic molding methods (see Plastic Processing). It is widely used, mainly used to manufacture films, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulation materials for televisions, radars, etc. With the development of petrochemical industry, polyethylene production has developed rapidly, and its output accounts for about 1/4 of the total output of plastics. In 1983, the total production capacity of polyethylene in the world was 24.65Mt, and the capacity of equipment under construction was 3.16Mt.