The most common use for polyurethanes in major appliances is rigid foams for refrigerator and freezer thermal insulation systems. Rigid polyurethane foam can be a cost-effective material used to meet required energy ratings in consumer refrigerators and freezers. The good thermal insulating properties of rigid polyurethane foams result from the combination of a fine, closed-cell foam structure and cell gases that are poor heat conductors. Modern refrigerators and freezers consist of a sheet metal outer casing and an inner liner made of ABS. In between these is a layer of rigid polyurethane foam that acts as both a structural and an insulating material that is applied and cured in appliance manufacturers’ assembly line. The adhesive properties of polyurethanes ensure a firm bond between the inner and outer walls, and also helps prevent heat exchange between the interior and exterior.