LOW-TEMPERATURES LATTICE THERMAL-CONDUCTIVITY OF NONCRYSTALLINE POLYMERS - APPLICATION TO POLYCARBONATE

The density fluctuation model is used to analyze the lattice thermal conductivity data of two samples of polycarbonate between 0.04 and 1K. The study is carried out by calculating the lattice thermal conductivity of a noncrystalline polymer as the sum of two contributions as K = K(BM)+ K(EM), where K(BE) is attributed to phonons which interact with the crystal boundaries, K(EM) is due to phonons which interact with the empty spaces. The relative importance of each contribution has also been examined by estimating their percentage contributions to the lattice thermal conductivity. An excellent fit to the experimental data was obtained over the whole temperature range.