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 +200o F. In general, however, polyethylenes are characterized by toughness, excellent chemical resistance and electrical properties, low coefficient of friction, near-zero moisture absorption and ease of processing.
Polyethylenes are classified into three categories, according to density:
Low
Medium
High
A fourth type ultrahigh molecular weight polyethylene (UHMWPE) is in the medium to high density range. Properties of this high-performance plastic are entirely different from those of conventional polyethylenes. Also available is crosslinked polyethylene, a special grade which, by chemical or irradiation treatment, becomes essentially a thermoset material with outstanding hear resistance and strength.
