Dependence of the thermal conductivity on mechanical stress in polymers

Abstract

Abstract An examination of the theory of thermal conductivity of amorphous dielectrics as applied to polymeric materials indicates that it is reasonable to expect that the conductivity is stress dependent. An experimental investigation was undertaken to determine the validity of this hypothesis for a number of plastics at temperatures below their respective glass transition points. Poly(methyl methacrylate), nylon, and Delrin were chosen as representative of a wide range of percentage crystallinity and were tested at compressive stresses up to 140 kg./cm. 2 and temperatures between 4 and 38°C. The results indicate that the conductivity may increase as much as 20% and that the dependence on stress is a function of temperature and the type of polymer examined.