In order to analyze the failure phenomenon of plastic liners in freezers and refrigerators the mechanical properties of the freon blown polyurethane (PU) foam insulator material and the acrylonitrile‐butadiene‐styrene (ABS) plastic liner are determined. The properties considered essential for this problem are the elastic modulus, the tensile strength and the fracture toughness over the temperature range −40 to 20°C. By laminating a layer of the polyurethane foam to the ABS liner and depending on the test temperature brittle to semi‐brittle fractures are promoted and the maximum load fracture toughness of the liner material is reduced. The reduction is more severe for notched bend than for single‐edge notched tension specimens. Based on these mechanical properties plausible reasons for liner fractures are discussed.