Applications of polymeric materials in electrical engineering increasingly require improvements in operating voltages, performance, reliability, and size reduction. However, the resulting increase on the electric field in electrical systems can prevent achieving these goals. Polymer composites, functionalized with conductive or semiconductive particles, can allow us to reduce the electric field, thus grading the field within the system. In this paper, a comprehensive review of field-grading materials, their properties, and recent developments and applications is provided to realize high-performance high-voltage engineering applications.

A graphene composite material suitable for facile drop-casting into flexible, conductive thin film electrodes from aqueous solution under ambient conditions is reported. This composite was applied to a polyethylene terephthalate substrate obtained from soda bottles. A solution of reduced graphene oxide with few layers (∼6 layers) was synthesized. The composites were prepared in two steps, first applying the reduced graphene oxide with surfactant and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) and then, solutions of poly-3-hexylthiophene with three different concentrations. Mild annealing was required only for the first step. The composite films exhibit more stability (mechanical and electrical) in bending tests when an intermediate amount of poly-3-hexylthiophene is applied. This composite is found attractive for flexible optoelectronic applications, promoting the reuse of one-use plastics.