Thermal and mechanical properties of polyimide nanocomposites

Interest has grown in recent years on the effects of nano-sized fillers on the thermal, mechanical, and electrical properties of polymeric systems. In particular, we are interested in studying the changes in mechanical and thermal properties of thermosetting polyimides as nano-sized fillers are added in increasing levels of concentration. The results are compared to micron-sized filled polyimides of similar compositions. We have observed dramatic increases in elongation to failure, scratch hardness and thermal conductivity while the tensile modulus does not change significantly. A change in stress state around nanoparticles during deformation is the possible reason for the observed improvement in tensile properties. Thermal conductivity of the filled polymer systems seemed to be most affected by the surface treatment of the nano-fillers. Improved interactions between the filler and the matrix is suggested as a possible explanation for these conductivity differences.

Introduction

Fillers are generally incorporated into the polymeric insulation for various. reasons, including discharge resistance, matching of the coefficient of thermal expansion, thermal conductivity enhancement, mechanical reinforcement and abrasion resistance [1]. The study of the effects of nanoparticles on dielectric properties of electrical insulation has grown significantly in recent years. Freschette and Lewis have reviewed the need and rational for the work [2], [3]. Nelson has examined the effects of nanofillers on space charge accumulation [4]. However, the understanding of insulation integrity of these nanocomposites is still in its infancy.