Erosion Suppression of Zinc Borate Filler in HTV Silicone Rubber under AC Dry-Band Arcing

This article investigates the erosion suppression mechanisms of zinc borate (ZB) in high-temperature vulcanized silicone rubber (SiR) using the IEC 60587 inclined plane test and simultaneous thermogravimetric (TGA)-differential thermal analysis (DTA). Alumina tri-hydrate (ATH) is employed in this study as a reference filler for comparison with ZB filler. The dehydration of ZB is reported to start around 350°C, whereas ATH starts dehydration at lower temperatures around 230°C. An insignificant difference is shown in the erosion resistance between the ATH and ZB-filled composites. Both fillers are shown viable in preventing the tracking and erosion failure in the IEC 60587 inclined plane test under the critical 4.5 kV ACrms voltage. ZB is found to suppress failure with the formation of residue acting as a shield against the progression of erosion. Whereas, ATH alleviates surface temperature by promoting an internal oxidation mechanism that suppresses combustion of SiR. This study's findings highlight the potential application of ZB as a cost-effective filler in high-temperature vulcanized SiR for outdoor insulation, particularly in regions where this filler is readily available.