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The temperature dependence of impact properties of polyurethane mouldings made by Reaction Injection Moulding (RIM), which are integral-skin foams with a sandwich structure consisting of high density skin and low density core layers, were investigated by instrumented Charpy impact tests. A remarkable difference in failure mode was observed depending on the layer composition and temperature. the failure modes obtained were classified as 1. tensile fracture-type and 2. buckling fracture-type. As the density ratio of the skin layer to the core layer increased or the temperature rose, the failure mode changed from the tensile fracture to the buckling fracture. Then the Charpy impact value became over two times greater with the change of failure mode, because the strain after the maximum impact load point increased remarkably. In addition, it was shown that there existed the density ratio that maximised the Charpy impact value and the fracture stress of the mouldings made by RIM when the overall density was kept constant. the results obtained here provide an important guide to determine the optimum layer composition concerning impact properties in the structural design of mouldings made by RIM, when such mouldings are applied to lightweight and thermal-insulating structural materials.

Temperature dependence on impact properties of rigid polyurethane moldings mode by RIM.