Dielectric breakdown of an epoxy/quartz composite and a nanostructured epoxy/quartz/Montmorillonite composite. Influence of electrode geometry

Microcomposites epoxies are widely used as high voltage insulation. A new way to improve such materials is to add nanoparticles to the epoxy matrix, thus forming a nanostructured microcomposite. For this study, epoxy composites films filled with 60% wt of quartz microparticles were prepared, reinforced or not by 0.45% wt of organically modified Montmorillonite C30B. The dielectric breakdown strength of the samples was studied using two types of electrode and the statistical analysis of the breakdown data was performed using the Weibull distribution. The use of different electrode geometries implied a different distribution of the electrical field magnitude both in the dielectric sample and in the surrounding medium. Rigid films with a typical thickness of 1 mm are set between electrodes embedded in oil and AC voltage was increased at a constant rate until breakdown occurs. No significant difference was found in the breakdown data for microcomposites and nanostructured composites. The use of a more uniform electrical field decreases slightly the measured dielectric breakdown strength. The shape factor associated with the distribution dispersion is unchanged for both studied cases, but very low compared to classical industrial materials. Finally, the thus obtained results warrant the use of smaller-area samples if non-uniform field conditions are used.