Polyethylene is one of the commonest thermoplastic resins in the world. It has excellent chemical and impact resistance.
Depending on the polymerisation process, polyethylenes can be "low density" (LDPE), "high density" (HDPE), linear (LPE) or high molecular weight (UHMWPE, for ultra high molecular weight).
LDPEs have good room temperature mechanical properties, good impact resistance and are good insulators even in damp environments. They also have good chemical inertia and can be used in the food industry (e.g. for bottled water).
HDPEs have similar properties to LDPE but are more rigid, have better creep and temperature resistance, a lower coefficient of friction and are more transparent.
LPEs have similar properties to HDPES, with better mechanical properties, still higher temperature creep resistance increased crack resistance.
UHMWPEs have the best mechanical properties. They are used in the field of composites to make reinforcing fibres with a density lower than 1 and enhanced mechanical properties, but unfortunately they have poor temperature resistance.