Influence of vulcanization factors on UV-A resistance of silicone rubber for outdoor insulators
Ying Lin, Fanghui Yin, Yuhao Liu, Liming Wang, Kangning Wu
Abstract
High temperature vulcanized silicone rubber (HTVSR) used outdoors is often deteriorated by ultraviolet (UV)-A radiation. UV-A resistance of HTVSR is related to network structures affected by vulcanization conditions (temperature, time, and pressure). To improve the UV-A resistance of HTVSR, an orthogonal experiment about vulcanization conditions was established. Mechanical properties, electrical properties, crosslink density, and Fourier transform infrared spectroscopy (FTIR) of a total of 747 HTVSR samples were measured during the UV-A aging process. Based on the change rates of the above properties, a comprehensive change degree index was proposed to assess the UV-A resistance. It was found that HTVSR vulcanized at 170°C, for 15 min, and under 12 MPa was endowed with excellent UV-A resistance due to the high crosslink degree, low content of -OH groups, and evenly dispersed fillers. They decreased the diffusion of oxygen and free radicals generated during the UV-A aging, the activity of silicone rubber to UV-A radiation, and the surface area of silicone rubber exposed to UV-A radiation. This statistical analysis result was verified by comparing HTVSR vulcanized under this condition with that vulcanized under other conditions in practice. This paper provides a potential approach to optimize UV-A resistance of HTVSR at the initial fabrication process.