Polyethylene (PE) is a thermoplastic resin polymerized from ethylene. In industry, it also includes * * * polymers of ethylene and a small amount of α-olefins. Polyethylene is odorless and non-toxic, feels like wax, and has excellent low temperature resistance (the lowest service temperature can reach-100 ~-70℃), good chemical stability and resistance to most acids and bases (not oxidative acids). Insoluble in general solvents at room temperature, low water absorption and excellent electrical insulation.
Polyethylene 1922 was synthesized by ICI Company in England, and 1933 Brennemen Chemical Industry Company in England discovered that ethylene can be polymerized to produce polyethylene under high pressure. 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 -olefin 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.