Performance evaluation of alumina trihydrate and silica-filled silicone rubber composites for outdoor high-voltage insulations

In recent years, silicone rubber-based composites have been widely investigated for outdoor applications due to their promising insulating properties. However, mechanical, thermal, and tracking properties of pure silicone rubber are very poor, which restrains its application for long-term performance. In this research work, the influence of microsized alumina trihydrate (ATH) and micro/nanosized silica (SiO2) fillers on mechanical, thermal, and electrical properties of room temperature vulcanized silicone rubber (RTV-SiR) has been studied. SiR-blends with varying amounts of ATH and SiO2 particles were prepared by blending in a two-roll mixing mill, compression molding, and postcuring processes in sequence. In order to evaluate relative tracking and erosion resistance of SiR-blends, an inclined plane test (IPT) was conducted in accordance with the ASTM D2303 standard procedure. Surface temperature distribution was recorded using a Fluke-Ti25 infrared camera during IPT experiments. Thermogravimetric analysis was carried out to analyze the thermal stability of ATH and silica-filled silicone rubber samples. Tensile strength, percent elongation at break, hardness, erosion, tracking resistance, and thermal properties were also investigated and discussed. Results showed that the mechanical, thermal, tracking, and erosion performances of SiR-blends are improved by the incorporation of ATH and silica particles, which is governed by filler type, size, and wt.% in the polymer matrix.