Temperature and pressure dependence of thermal conductivity measurement of polystyrene and polycarbonate

The thermal conductivity of polymers in the solid and molten phases, as functions of temperature and pressure, is an essential parameter to permit simulation of polymer processing by computer-aided engineering (CAE). A key factor for the thermal conductivity when used in CAE is the Bridgman parameter (g) as a function of temperature. This is experimentally examined for polystyrene (PS) and polycarbonate (PC) in this paper. It was demonstrated that the thermal conductivity results under pressure were well described by the Eiermann's equation. First, the product of the Bridgman parameter (g) and the compressibility (beta) as a function of temperature was calculated by fitting the experimental values with the Eiermann's equation. Second, the compressibility (beta) as a function of temperature was estimated from the slope, in a plot of specific volume as a function of pressure. Finally, the Bridgman parameter (g) as a function of temperature was obtained from the two previous figures. The Bridgman parameters from the experiments are discussed by comparing them with those from Eiermann's theoretical model.