Polyethylene is a thermoplastic polymer consisting of long hydrocarbon chains. De­pending on the crystallinity and molecular weight, a melting point and glass transi­tion may or may not be observable. The temperature at which these occur varies strongly with the type of PE. For common commercial grades of medium — and high — density polyethylene (MDPE, HDPE) the melting point is typically in the range 120 to 130 °C (248 to 266 °F).

Most LDPE, MDPE and HDPE grades have excellent chemical resistance, meaning that it is not attacked by strong acids or strong bases. It is also resistant to gentle oxidants and reducing agents. PE burns slowly with a blue flame having a yellow tip and gives off Adour of paraffin. The material continues burning on re­moval of the flame source and produces a drip. Crystalline samples do not dissolve at room temperature. PE (other than cross-linked polyethylene) usually can be dis­solved at elevated temperatures in aromatic hydrocarbons such as toluene or xylene, or in chlorinated solvents such as trichloroethane or trichlorobenzene.