Polyethylene (PE), light, versatile synthetic resin made from the polymerization of ethylene. Polyethylene is a member of the important family of polyolefin resins. It is the most widely used plastic in the world, being made into products ranging from clear food wrap and shopping bags to detergent bottles and automobile fuel tanks. It can also be slit or spun into synthetic fibres or modified to take on the elastic properties of a rubber.
Ethylene (C2H4) is a gaseous hydrocarbon commonly produced by the cracking of ethane, which in turn is a major constituent of natural gas or can be distilled from petroleum. Ethylene molecules are essentially composed of two methylene units (CH2) linked together by a double bond between the carbon atoms—a structure represented by the formula CH2=CH2. Under the influence of polymerization catalysts, the double bond can be broken and the resultant extra single bond used to link to a carbon atom in another ethylene molecule. Thus, made into the repeating unit of a large, polymeric (multiple-unit) molecule, ethylene has the following chemical structure:.
This simple structure, repeated thousands of times in a single molecule, is the key to the properties of polyethylene.