Synergistically Improving Tracking Resistance of Addition-Cure Liquid Silicone Rubber with Aminepropyltriethoxysilane-Immobilized Silica and Platinum Catalyst

The tracking-resistant silicone rubber with superior water resistance is very essential for outdoor high-voltage transmission field. In this work, aminepropyltriethoxysilane-immobilized silica (APTES-SiO₂) was prepared through dehydration condensation between the ethoxy groups of aminepropyltriethoxysilane (APTES) and hydroxyl groups on the SiO₂ surface. The effects of APTES-SiO₂ on the vulcanization, mechanical properties, thermal stability and tracking resistance of addition-cure liquid silicone rubber (ALSR) were studied. The results revealed that APTES-SiO₂ and platinum catalyst (Pt) synergistically improved the tracking resistance of ALSR, and APTES-SiO₂/ALSR also possessed excellent water resistance. When the content of APTES and Pt was 0.15 phr (parts per hundreds of rubber) and 15 ppm (parts per million), respectively, APTES-SiO₂/ALSR reached 1A4.5 level. Furthermore, the tracking resistance of ALSR showed little deterioration even after immersion in water for 30 days. The results of thermogravimetry (TG) and thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) indicated that APTES-SiO₂ and Pt synergistically promoted the radical crosslinking of ALSR chains at high temperature, which was favorable to the formation of compact ceramic protected layer, thus significantly improved the tracking resistance of ALSR.