High-Molecular Weight / High-density polyethylene
Polyethylene has very good impact properties in cold and hot weather. It has high molecular weight and good environmental stress crack resistance (ability to contract and expand numerous times before cracking). Polyethylene is a very stable molecule, so it provides good chemical resistance. Polyethylene does have a high coefficient of expansion, meaning that it has large dimensional changes in different temperature conditions; this must be accounted for in product design. Paint and adhesives do not adhere well to polyethylene, unless extensive surface treatment has occurred.