Aging mechanism of HTV silicone rubber loaded with hybrid nano/micro silica and alumina exposed to concurrent multistress

Due to their many benefits, especially their high hydrophobicity, silicone rubber-based composite materials gradually substitute conventional porcelain and glass insulators. However, polymeric-based materials are degraded when subjected to various external environmental stresses, which deteriorates their anticipated qualities and shortens their lifetime. This study investigates the aging characteristics of five types of high-temperature vulcanized silicone rubber (HTV-SR) filled with nano-silica/micro-alumina. Samples of materials with different specifications were subjected to various environmental conditions in a specialized weather chamber for 5000 h. The degree of deterioration was analyzed using multiple diagnostic methods: hydrophobicity categorization, fourier transform infrared spectroscopy, leakage current, mechanical property testing, and thermogravimetric analysis. The experimental results showed that SR impregnated with low-level nano silica filler revealed superior anti-aging properties compared to its high concentration and unfilled counterpart. SP-3 (2% nano-silica and 10% micro-alumina) displayed the lowest surface roughness and the best hydrophobicity among the composite test samples. In addition, the highest tensile strength (4.1 MPa) and lowest leakage current (2.5 μA) were recorded. The composite containing 2% nano-silica appears to be the highest resistance candidate to the multi-stress aging test, which can be explained by the strong molecular contact amongst nano-silica and SR.