It is a thermoplastic resin polymerized from ethylene. Polyethylene is a semi-crystalline thermoplastic material. Their chemical structure, molecular weight, degree of polymerization and other properties largely depend on the polymerization method used. The polymerization method determines the type and degree of branching. The crystallinity depends on the chemical structure and processing conditions of the polymer.

In industry, it also includes * * * polymers of ethylene and a small amount of α-olefins. Polyethylene is odorless and nontoxic, feels like wax, and has excellent low temperature resistance (the lowest service temperature can reach -70 ~- 100℃), good chemical stability, resistance to most acids and alkalis (oxidation-resistant acids), insolubility in general solvents at room temperature, low water absorption and excellent electrical insulation.

History of polyethylene research;

Polyethylene was first synthesized by ICI Company in England in 1922. 1933, British Bremen Chemical Industry Company discovered that ethylene can be polymerized under high pressure to produce polyethylene. This method was industrialized in 1939, commonly known as high-pressure method. In 1953, K. Ziegler of the Federal Republic of Germany found that ethylene can be polymerized at lower pressure with TiCl4-Al(C2H5)3 as catalyst.

This method was put into industrial production by Hearst Company of the Federal Republic of Germany on 1955, commonly known as low-pressure polyethylene. In the early 1950s, Philip Oil Company of the United States found that ethylene could be polymerized under medium pressure to produce high-density polyethylene with chromium oxide-silica-alumina gel as catalyst, and it was industrialized in 1957. In 1960s, DuPont Company of Canada began to prepare low density polyethylene from ethylene and α -olefins by solution method.

During the period of 1977, Union Carbide Company and Dow Chemical Company successively prepared low-density polyethylene by low-pressure method, which is called linear low-density polyethylene, and the gas phase method of Union Carbide Company is the most important. Linear low density polyethylene (LDPE) has similar properties to LDPE and some characteristics of high density polyethylene. In addition, because of its low energy consumption in production, it has developed rapidly and become one of the most striking new synthetic resins.