The impact of nanocomposite formulations on electrical voltage endurance

Previous work in which a conventional micron-sized filler was replaced by nanomaterials in an epoxy matrix has shown significant, and encouraging enhancements in the electric strength of the composites. The advantages gained were associated with the mitigation of Maxwell-Wagner polarization and the internal associated space charge, and an optimum particulate loading established. This contribution seeks to extend the previous work, by examining the electrical voltage endurance and partial discharge in a divergent field geometry. The voltage endurance tests demonstrate that significant improvements in endurance are also indicated. Similar results are seen in the partial discharge measurements. In order to gain a mechanistic understanding, the same electrode configuration has also been subjected to electroluminescence experiments in which both the steady-state and temporally-resolved light emission has been compared in these materials. Changes in the magnitude and onset field of the emission suggest that both the enhanced scattering of the nanocomposite and the mitigation of internal charge play a pivotal role in the enhanced voltage endurance obtained. Microscopy, dielectric spectroscopy and free volume measurements are also introduced to provide insight into the possible underlying mechanisms involved.