Influence of vulcanization factors on UV-A resistance of silicone rubber for outdoor insulators

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.