Polyethylene, which we called PE, is the most popular product in the plastic industry. Polyethylene is a kind of thermoplastic obtained by ethylene. PE has following features:odorless, non-toxic, feeling like wax, excellent low temperature resistance(minimum operating temperature can reach -100 to -70℃）, good chemical stability and can resist most acid and alkali erosion(not resistant to oxidation nature acid), insoluble in common solvents at room temperature,low water absorption and excellent electrical insulation. PE is generally used in plastic wrap, plastic bag, milk bottles,pails, water bottles and etc.

PE was created by British company Imperial Chemical Industries(ICI) in 1922 and industrially produced in 1939 in the U.S. It was widely used for radar’s insulation materials and military supplies during WWII. After the WWII, Japan’s Mitsui Chemical and Sumitomo started to produce PE in 1958.

In 1933, British company Brunner Mond&Co found that PE could be polymerized by ethylene under high pressure. This method was industrialized in 1939 and was known as high pressure method. In 1953, Federal Republic of Germany’s chemist, K.Karl Ziegler found that PE cloud be generated under low pressure with TiCl4-Al(C2H5)3 as catalyst. This method was industrialized by Germany’s Hoechst company in 1955. Also, this method was called low pressure method.

In the early 1950s, Philips Petroleum Company of U.S. discovered that using chromium oxide-silica alumina as catalyst, ethylene could be polymerized to form high-density PE under medium pressure. This method was industrialized in 1957.

In the 1960s, DuPont company began to produce low-density PE with ethylene and α-olefin.

In 1977, Union Carbide Company and Dow Chemical Company of the U.S. used low pressure method to produce low-density PE. This product was called linear low-density PE. The performance of linear low-density PE was similar to the low-density PE, meanwhile it had some features of high-density PE. In addition, the cost of energy to produce linear low-density PE is lower than others, it became the most popular resin material.

The core technology of low pressure method was the catalyst. The TiCl4-Al(C2H5)3 was the first generation of catalyst for PE which had low efficiency(1g of titanium can only get 1kg of PE). In 1963, Solvay Company of Belgian created the second generation of catalyst with magnesium compound. The efficiency of this catalyst was improved a lot(1g of titanium can get 10kg-100kg PE). In addition, the use of the second generation catalyst can save the post-treatment process for removing catalyst residues.

In 1975, the Monte Edison Group of Italy developed a catalyst that can directly produce spherical PE without granulation. It was called the third generation catalyst, which was the revolution of high-density PE.

PE is a crystalline thermoplastic resin. Its chemical structure, molecular weight, degree of polymerization and other properties is largely dependent on the polymerization method. The polymerization method determines the type and degree of branching. The degree of crystallization depends on the regularity of the molecular chain of the part and its thermal history.

In 1983, the total production capacity of PE in the world was 24.65Mt, and the capacity of the units under construction was 3.16Mt.

In 2011, the global production capacity has reached 96Mt. The development trend of PE production showed that production and consumption were gradually shifting to Asia. China became the most important consumer market.