Thermal conductivity of polypyromellitimide film with alumina filler particles from 4.2 to 300 K

Abstract

The thermal conductivities of several types of a commercial polyimide (namely polypyromellitimide, PPMI) film were measured over a range of temperatures from 4.2 to 300 K with an unguarded steady state parallel-plate apparatus. Specimens were made by stacking multiple layers of film together. Conductive grease was used between the layers of film to reduce thermal contact resistance. Two specimens were made from two different types of neat film with a thickness of 76 μm, and three specimens were made from films that contained two different amounts of alumina filler and had thicknesses of 25 or 76 μm. The conductivity of PPMI film increases with the amount of alumina filler present. The thermal conductivity of specimens made from film of the same type but of different thickness is independent of film thickness, within the limits of experimental uncertainty. The conductivity of a specimen subjected to a simulated curing process by being held at a temperature of 150°C for 90 min was indistinguishable from that of a similar, control specimen not subjected to such treatment.