For Polyethylene PE, full name, is the most simple structure of high polymer organic compound, the world's most widely used polymer materials, composed of ethylene polymerization, depending on the density is divided into high density Polyethylene, medium density Polyethylene and low density Polyethylene. Low density polyethylene is soft and is used for high pressure polymerization. High density polyethylene has the characteristics of rigidity, hardness and mechanical strength and is used for low pressure polymerization. Hdpe can be used for containers, pipes, and high frequency electrical insulation for radar and televisions. Low density (high pressure) polyethylene is often used in large quantities. Polyethylene is waxy with a waxy smoothness. When not stained, low-density polyethylene is transparent while high-density polyethylene is opaque.
Polyethylene is a high polymer chain formed from repeated - CH2 - units through addition and polymerization of ethylene (CH2=CH2). The properties of polyethylene depend on the way it is polymerized. High density polyethylene (HDPE) was synthesized by ziegler-natta polymerization at medium pressure (15-30 atmospheres) catalyzed by organic compounds. Polyethylene molecules polymerized under these conditions are linear and have very long chains, with molecular weights up to several hundred thousand. Under the condition of high pressure (100-300 mpa), high temperature (190 -- 210 C) and peroxide catalyzing radical polymerization, the product is low-density polyethylene (LDPE), which is branched structure.
Polyethylene is insoluble in water, water absorption is very small, is to some chemical solvents, such as toluene, acetic acid, and only in the above 70℃ temperature slightly dissolved. However, particulate polyethylene can melt or solidify with the change of temperature between 15℃ and 40℃. When the temperature rises, it melts and absorbs heat. When the temperature drops, it solidifies and gives off heat. Because its water absorption is very small again, not easy and moist, have insulation property, it is very good building material accordingly.