Polyethylene
PE
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Definition:
A family of resins prepared from the polymerization of ethylene gas using a variety of catalysts. Density, melt index, crystallinity, degree of branching and cross-linking, molecular weight and molecular weight distribution can be regulated over wide ranges. Further modifications are obtained by copolymerization, chlorination, and compounding additives. Polymers with densities ranging from about 0.910 to 0.925 are called low density polyethylene, those of densities from 0.926 to 0.940 are called medium density, and those of densities from 0.941 to 0.965 and over are called high density polyethylene. The low density types are polymerized at very high pressures and temperatures, and the high density types at relatively low pressures and temperatures. Two other types are extra high molecular weight (EHMW) materials having molecular weights in the range 150,000 to 1,500,000 and ultra high molecular weight (UHMW) materials in the 1,500,000 to 3,000,000 range. When fully cross-linked by irradiation or by the use of chemical additives, they are no longer thermoplastics. Cured during or after molding they become true thermosets with good tensile strength, electrical properties and impact strength over a wide range of temperatures. Glass fiber reinforced polyethylene can be processed by injection molding, rotational molding, and blow moldings.
Definition Copyright ©1989 CRC Press LLC. All rights
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