The effects of high electric fields on an Epoxy resin

The aim of this work was to determine some of the effects caused by the application of a high electric field on a filler-free epoxy resin material. Two types of sample geometry were moulded. Films (55 to 300μm) were prepared to work under uniform field configurations. A frame of parallel wires (5 to 25μm radius) was introduced into the bulk to work under divergent fields. Three non-destructive complementary methods of investigation were used. In all cases the first measurements were performed before the application of thermal-electric stress to define the properties of the material itself. Measurements were repeated after a controlled period of stress. Dielectric spectroscopy measurements were used to determine the main relaxation processes. To evaluate the impact of charge injection and localise the build up of space charge, the pulsed-electro acoustic method was chosen. Luminescence experiments were carried out to investigate the luminescence excitation parameters and pathway of radiative relaxation that are found to be directly linked with the charge injection and extraction phenomena. In addition spectral analysis was performed to complete the investigation. Light emission is associated with relaxations dependent on the chromophores that are present and that are likely to be affected by an external stress. After thermal-electric stress one relaxation processes was detected by dielectric spectroscopy that was dependent on the stress. This was associated with a change in the local arrangement of the chemical network, which is altered by the field. A mechanism of trapping and de-trapping of charge was determined by the analysis of the PEA response, light emission analysis coupled with external current. The studies were completed by a computer simulation of the effect of injected charge on the electric field. The three techniques were found to be useful complementary tools to determine the effects of stress on this insulation material.