Thermal Properties of Crystalline Polymers at Low Temperatures

In comparison with inorganic solids there have been few studies of the low temperature thermal properties of polymers, even though these properties are of considerable interest in scientific research and cryogenic technology. From the three important thermal quantities, heat capacity Cp, thermal conductivity K and thermal expansion α, the heat capacities of polymers have been most widely studiedi1. Most of the studies on thermal conductivity of polymers are confined to the range between liquid nitrogen and room temperature. Recently, however, the situation has improved and thermal conductivity data2 for polymers are now available in the temperature range 0.1 to 300K. In contrast, there is a lack of data on thermal expansion measurements at low temperatures. On the other hand there has been a growing theoretical interest in the lattice dynamics of polymers representing a rather extreme form of anisotropy in the crystalline state3.