Polyethylene, the largest volume thermoplastic polymer used today, is available in a wide variety of grades and formulations that have an equally wide range of properties. Some polyethylenes are flexible, others are rigid; some have poor impact strength, others are virtually unbreakable; some have good clarity; others are opaque. Service temperatures can range from -40° to +200°F. In general, however, polyethylenes are characterized by toughness, excellent chemical resistance and electrical properties, low coefficient of friction, near-zero moisture absorption, light weight (approximately one-eighth that of steel) and ease of processing.
Polyethylenes are classified into three categories, Low, Medium, and High density.
A fourth type, ultra-high-molecular-weight-polyethylene (UHMW-PE), is in the high-density range. In some cases, properties of this high-performance plastic are similar to other polyethylenes, but in other cases, can be dramatically different. Also available is crosslinked polyethylene, a special grade which, by chemical or irradiation treatment, becomes essentially a thermoset material with outstanding heat resistance and strength.