LOW-TEMPERATURE THERMAL-PROPERTIES OF AMORPHOUS POLYCARBONAT

The thermal conductivity lambda, the specific heat c and the thermal e xpansion alpha of isotropic Polycarbonat (PC) and of PC after stretchi ng were measured in the temperature ranges between 0.1 K and 80 K (lam bda, c) and between 4 K and 300 K (alpha). The measurements show the t ypical low-temperature behavior of amorphous solids. Below 20 K the re sults can be explained in the framework of the soft potential model. A bove 20 K with increasing temperature the thermal conductivity and the thermal expansion show between 30 K and 50 K a distinct decrease in s lope of the temperature dependence. PC, stretched at 438 K with a load of 2 kN, shows a high anisotropy in these two thermal properties.