The Thermal Transport Properties of Polymers

Values of thermal diffusivity and thermal conductivity are needed for heat-flow calculations, for the determination of structure-property relationships, and for material selection and comparison. However, all aspects are hampered by a dearth of reliable data and anything more than a superficial glance at the literature is apt to be discouraging for the uninitiated. Hardly any thermal diffusivity data exist, and the reported values of thermal conductivity show very large scatter. The present state of confusion can be seen, for example, in Figures 1 and 2, which show the reported thermal conductivity values for polystyrene and gum natural rubber. Not only do the values differ at some temperatures by more than 100%, and in the case of rubber by almost 300%, but different trends are indicated throughout the temperature range. Discrepancies of this size cannot be due to sample variations, and they give some indication of the experimental difficulties associated with thermal property measurements.