Polyethylene

Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most common plastic in use today. It is a linear, man-made, addition, homo-polymer, primarily used for packaging (plastic bags, plastic films, geomembranes, containers including bottles, etc.). As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market.

Many kinds of polyethylene are known, with most having the chemical formula (C2H4)n. PE is usually a mixture of similar polymers of ethylene, with various values of n. It can be low density or high density: low density polyethylene is extruded using high pressure (1000-5000 atm) and high temperature (520 Kelvin), while high density polyethylene is extruded using low pressure (6-7 atm) and low temperature (333-343 Kelvin). Polyethylene is usually thermoplastic, however it can be modified to become thermosetting instead, for example in cross-linked polyethylene.