Non-linear Field Grading Materials and Carbon Nanotube Nanocomposites with Controlled Conductivity

Abstract

Coincident with many applications requiring dielectric materials is the need for filled polymers with tailored conductivity and non-linear resistivity as a function of electric field. For example, in cable terminations, field grading materials are used to reduce the field concentrations at the joint. The field grading materials can be materials with high capacitance, or materials that exhibit non-linear resistivity with field. Applications requiring electromagnetic interference shielding also take advantage of filled polymers with high conductivity. This chapter focuses on the electrical properties of semiconducting nanoparticle filled polymers and carbon nanotube filled polymers with an emphasis on the effect of particle size, shape, dispersion, alignment, and percolation state on the behavior. A brief introduction to relevant applications is followed by a review of relevant percolation theory. This is followed by a discussion of the field grading literature and an introduction to the potential mechanisms leading to non-linearity. Finally, a brief review of conductivity in nanotube filled polymers with a focus on the control of conductivity is provided.