A linear polymer, High Density Polyethylene (HDPE) is prepared from ethylene by a catalytic process. The absence of branching results in a more closely packed structure with a higher density and somewhat higher chemical resistance than LDPE. HDPE is also somewhat harder and more opaque and it can withstand rather higher temperatures (120o Celsius for short periods, 110o Celsius continuously). High density polyethylene lends itself particularly well to blow molding, e.g. for bottles, cutting boards, dipping baskets, dippers, trays and containers.