Enhancement of tracking and erosion resistance of silicone rubber with platinum/amino-silane by modulation of crosslinking density

Tracking and erosion resistance of silicone rubber with N-[3-(trimethoxysilyl)propyl]aniline (NTSPA) and Karstedt catalyst (Pt) was improved significantly by increase of crosslinking density through incorporation of polymethylvinylsiloxane with high vinyl content of 2.93 mol% (HPMVS). Silicone rubber with 15 phr of HPMVS passed the incline plane test (IPT) at 4.5 kV with eroded mass of merely 0.65 wt%, whereas silicone rubber without HPMVS failed the test. TGA and TG-FTIR results indicate that increase of crosslinking density facilitated radical crosslinking reactions induced by Pt/NTSPA at elevated temperature. Residues from silicone rubbers after IPT were characterized via Raman spectroscopy,
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Si NMR and SEM. The results reveal that highly crosslinked network promoted formation of a compact silicon oxycarbide ceramic barrier to protect inner material from further degradation during dry band arcing. Moreover, conductive graphitic carbon in the residue decreased remarkably, thereby inhibiting the formation of conductive path.