The Plastics Collection

Polyethylenes are a family of resins obtained by polymerizing ethylene gas, creating a thermoplastic polymer consisting of long hydrocarbon chains. Polyethylene is made in different grades. By varying the catalysts and methods of polymerization, properties such as density, melt index, crystallinity, degree of branching and cross-linking, and molecular weight distribution can be regulated over wide ranges. Low molecular weight polymers of ethylene are fluids used as lubricants; medium weight polymers are waxes miscible with paraffin; and the high molecular weight polymers are the familiar, rough, leathery resins used in the plastics industry in the highest volume of all plastics. When fully cross-linked by irradiation or by the use of chemical additives, polyethylene is no longer a thermoplastic. When cured during or after molding, it becomes a true thermoset with good tensile strength, electrical properties and impact strength over a wide range of temperatures.
 
Many iconic plastic products, such as Tupperware, are made of polyethylene. Since the 1940's, polyethylene has been most visible in packaging, especially as plastic bags and plastic film. Polyethylene foam is used in packaging, vibration damping and insulation, as a barrier or buoyancy component, or as material for cushioning.
 
Polyethylene was first synthesized by the German chemist Hans von Pechmann who prepared it by accident in 1898 while heating diazomethane. His colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy, substance and recognized that it contained long -CH2- chains and termed it polymethylene. The first industrially practical polyethylene synthesis was discovered (again by accident) in 1933 by Eric Fawcett and Reginald Gibson at the Imperial Chemical Industries (ICI) works in Northwich, England.

See also Chlorinated PE (CPE), Cross-linked PE (XLPE), High Density PE (HDPE), Linear Low Density PE (LLDPE), Low Density PE (LDPE), and Ultra High Molecular Weight PE (UHMWPE).
 
Sources:
J. A. Brydson, Plastics Materials, 4th ed., 187-189.
Whittington’s Dictionary of Plastics, 2nd ed., 247-248.