Aging Mechanism of Silicone Rubber Under Thermal–Tensile Coupling Effect

Silicone rubber (SR) is widely used as insulation for cable accessories and the aging behavior significantly affects the cable operation. This study aimed to investigate the aging performance and mechanism of SR subjected to thermal effect and different mechanical tensions for up to 1000 h. We measure the crosslink density, mechanical and electrical properties to evaluate property variations, and material characterization methods, such as Fourier transform infrared spectrum and X-ray photoelectron spectroscopy (XPS), are conducted to explore the aging mechanism. Based on comprehensive analyses, competitive effects and synergistic effects between thermal aging and tensile aging are demonstrated. Thermal aging increases the crosslink density and improves the dielectric property, while tensile aging exhibits the opposite effects. Nevertheless, the effects of tensile aging on mechanical properties, especially stress relaxation, are significantly promoted by thermal aging. These complex effects can be attributed to the destruction of physical crosslink and the orientation of molecular chains induced by tensile stress.