2004 Volume 32 Issue 3 Pages 145-147
For evaluation of thermal endurance in foamed plastics, temperature and time characteristics of compression dynamic modulus of four hard polyurethane foams were investigated by the dynamic viscoelastic measurements. Compression dynamic modulus of each polyurethane foams lessened gradually with time, probably due to a decrease of inner pressure of closed-cell, which influenced stiffness of foam skeletons. Logarithm of time t, at which the compression dynamic modulus came to be 50% of its initial value at the beginning of the dynamic measurement has been found to be a linear function of reciprocal of the absolute temperature T− 1. Thermal endurance characteristics can be evaluated from the linear relations between log t and T −1.
