Polyethylene 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 (the minimum use temperature can reach -100~-70°C), has good chemical stability, and can withstand most acids and alkalis (not resistant to oxidation) Nature of acid). It is insoluble in general solvents at room temperature, has low water absorption and excellent electrical insulation.

Polyethylene is very sensitive to environmental stress (chemical and mechanical effects), and its resistance to heat aging is worse than the chemical structure and processing of polymers. Polyethylene can be processed by general thermoplastic molding methods. It has a wide range of uses, mainly used to make films, packaging materials, containers, pipes, monofilaments, wires and cables, daily necessities, etc., and can be used as high-frequency insulation materials for TVs, radars, etc.

With the development of petrochemical industry, polyethylene production has developed rapidly, and the output accounts for about 1/4 of the total output of plastics. In 1983, the total production capacity of polyethylene in the world was 24.65 Mt, and the capacity of installations under construction was 3.16 Mt. According to the latest statistics in 2011, the global production capacity reached 96 Mt. The development trend of polyethylene production shows that production and consumption are gradually shifting to Asia, and China is becoming the most important consumer market.

Polyethylene resin is a non-toxic, odorless white powder or granule, with a milky white appearance, a wax-like hand, and a low water absorption rate of less than 0.01%.

The polyethylene film is transparent and decreases with the increase of crystallinity. Polyethylene film has low water permeability but high air permeability, which is not suitable for fresh-keeping packaging but suitable for moisture-proof packaging. It is flammable and has an oxygen index of 17.4. It has low smoke during combustion, with a small amount of molten droplets, yellow on the flame and blue underneath, with a paraffin odor. Polyethylene has better water resistance. The surface of the product is non-polar, and it is difficult to bond and print. It is improved by surface treatment. Many branches have poor resistance to light degradation and oxidation.

Its molecular weight is in the range of 10,000 to 100,000.

Those with a molecular weight of more than 100,000 are ultra-high molecular weight polyethylene. The higher the molecular weight, the better the physical and mechanical properties and the closer to the required level of engineering materials. But the higher the molecular weight, the more difficult its processing. The melting point of polyethylene is 100～130℃, and it has excellent low temperature resistance. It can still maintain good mechanical properties at -60°C, but the use temperature is 80~110°C. [5]

It is insoluble in any known solvents at room temperature, and can be dissolved in toluene, amyl acetate, trichloroethylene and other solvents in a small amount above 70°C.