Tracking and Erosion of Polydimethlysiloxane With Different Molecular Weight for Outdoor Insulation

In this article, the degradation mechanisms of unfilled polydimethylsiloxane with different molecular weights are investigated under dry-band arcing using the inclined plane tracking and erosion test and material characterization techniques. Tracks of carbonaceous residue formed as byproducts of radical-based crosslinking are prevalent over erosion as the molecular weight increases. Erosion becomes dominant with polydimethylsiloxane that undergoes mainly depolymerization during degradation at lower molecular weights. Accordingly, tracking due to a progressive carbonaceous residue formed on the surface is the degradation pattern observed under the dry-band arcing for the polydimethylsiloxane with higher molecular weights (45 000 and 28 000 g/mol) during the inclined plane test (IPT), whereas erosion due to depolymerization is more evident on the polydimethylsiloxane surfaces with lower molecular weights (17 200 and 9400 g/mol). This study highlights the possibility to tune the tracking and erosion tendency of silicone rubber outdoor insulation by controlling the molecular weight of the organosiloxane base, without the sole reliance on fillers as commonly perceived.