Electrical properties analysis of nano-filled epoxy by space charge characterization

Numerous studies have shown that the presence and/or development of electric charges within polymers affect their properties with a significant order. These charges, intrinsic or extrinsic, that are called space charges, have been first observed for polymers used for electrotechnical applications, thus, at high electric fields. In many other studies, it has been observed that space charges are present into the polymers, even if these polymers were not exposed to additional stresses other than those associated with their synthesis and making. Moreover, the increase of the space charges seems directly linked with the deterioration of the physical properties of these materials since charge trapping is mainly associated with structure defects. These defects may have several origins, namely fabrication, interfaces, and stresses applied to the material. In this work, electrical properties of epoxy microcomposites with and without nanoclay are investigated under different conditions: without initial stress, and with subsequent electrical and thermal stresses. Correlating space charge measurements obtained by the Thermal Step Method with results observed in thermally stimulated-current experiments, the nature of the observed electric charges and the influence of the nanostructures can be discussed. Results and their scattering for cases including samples with and without nanoclay point certainly at the importance of the quality of the fabrication process.