Surface degradation studies in polymer dielectrics with nano-sized fillers

Recent research has indicated that dielectric properties of polymer insulating materials might be improved by the inclusion of nano-sized particles dispersed through the polymer matrix. Dielectrics in power apparatus are often exposed to surface discharges in the course of normal operation. Surface degradation due to continued exposure to such discharges may cause deterioration of the surface, and could ultimately lead to catastrophic failure. The current work investigates the manner in which inclusion of nanometric particles affects the resistance of the polymer to surface degradation. Bisphenol-A type epoxy resin was selected as the polymer matrix. The filler material used in the dielectric composite was spherical alumina powder of average diameter 40 nm. Surface discharge tests were carried out on the specimens. The degraded specimens were studied using a high resolution camera and a scanning electron microscope (SEM). Surface roughness measurements were taken using a surface laser profilometer. It was observed that degradation was greater for unfilled epoxy specimens. The effect of variation of the nano-filler content was also studied. Clearly, addition of nano-particles helped prevent surface degradation due to surface discharges.