THERMOELASTIC EFFECT IN GLASSY POLYMERS

In the reported experiments, the thermoelastic effect has been measured in compression on four glassy polymers; namely, polystyrene, poly(methyl methacrylate), polycarbonate, and epoxy resin. The polymers are shown to obey the classical Thompson equation for thermoelasticity in solids over the temperature range studied (ca. 220-350 degree K). By inference such materials can be expected to behave classically in general. The results have been used, as first suggested by Trainor and Haward, to obtain values for the linear thermal expansion coefficient and the values so obtained are shown to be in excellent agreement in general, with literature values obtained by more conventional methods. Results are given for a range of stress from 5 MN m** minus **2 to between 25 and 50 MN m** minus **2 according to ambient temperature. The method affords a measurement of parameters, in particular, linear thermal expansion coefficient. Values of specific heat for the four plastics have been measured by differential scanning calorimetry and the results compared with published data.