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

The density fluctuation model is used to analyze the lattice thermal c onductivity data of two samples of polycarbonate between 0.04 and 1K. The study is carried out by calculating the lattice thermal conductivi ty 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 t he empty spaces. The relative importance of each contribution has also been examined by estimating their percentage contributions to the lat tice thermal conductivity. An excellent fit to the experimental data w as obtained over the whole temperature range.