plastic molding term
plastic molding term Heat-distortion temperature (°F) at fiber stress of 264 psi (ASTM D 648) is a statement of the temperature required to permit an arbitrary standard amount of deflection by a standard load, in a test in which the specimen is subjected to a gradually increasing temperature. It is thus an indication of the ability of a material to retain its stiffness, or resistance to deformation, against the weakening influence of high temperature. A similar test，under the lower load of 66 psi (ASTM D 648), in which, of course, a higher temperature is recorded, has similar significance for material subjected to lighter load. Values determined by this second test are shown, for some materials, in the 6th column of the table. A large difference between heat-distortion temperatures in these two tests gives warning of the need to pay particular attention to designing so as to minimize the stress in service of articles subjected to heat. Impact strength , Izod {ft-lb per iti. of notch...