2004 zyxwvutsr Annual Report Conference on Electrical Insulation and Dielectric Phenomena Comparison between Silicone Rubber containing Micro- and Nano- Size Silica Fillers A. H. El-Hag S.H. Jayaram E.A. Cherney Electrical and Computer Engineering Department University of Waterloo Waterloo. Ontario, Canada Abstract: In this study the influence of nanesize silica filler is compared with micro-size filler in silicone rubber using the ASTM 2303 inclined plane tracking and erosion test. Silicone rubber samples filled with 5 pm mean size ground silica are compared with silicone rubber filled with zyxwvutsrq 12 nm average size fumed silica. Both the low frequency components of leakage current and eroded volume are used to evaluate the performance of the two types of composites. While the fundamental component of leakage current does not correlate with the erosion, the third harmonic component of the leakage current shows good correlation to the erosion, in terms of volume, and for both composites. Based on the results of the eroded volume, it is observed that 10% by weight of nano-size filler in the silicone rubber gives a performance that is similar to that obtained with 50% by weight of micro-size filler. The paper discusses the merits of nano-size filler in silicone composites. Introduction Silicone tubber (SIR) has been used as an insulating material for outdoor applications for more than 30 years. Compared to ceramic insulators, SIR insulators have advantages of g o d pollution performance, reduced weight and lower cost [I]. However, aging is still considered the main problem facing SIR insulators. To improve the aging performance of silicone rubber insulators various types of fillers are needed. Fillers are added to silicone rubber to reduce cost, improve dry band arcing resistance and to improve mechanical properties. Extensive research zyxwvut has been conducted to study the influence of filler size, concentration and type on the aging performance of SIR insulators f3-51. However, much of the previous efforts have concentrated on micro-size fillers. With the growing interest in using nano-size tillers in polymeric materials, the use of these fdlers could have a strong influence on the performance of SIR insulators. Although fumed silica has been extensively used for reinforcement of silicone rubber, its role on the erosion and tracking resistance has not been studied. This paper presents a comparison between nano-size silica filled SIR with micro-size silica filled SIR samples using the ASTM 2303 standard inclined plane tracking and erosion test zyxw (IPT). A companion paper discusses the underlying physicochemical properties of fumed silica filled SIR composites zyxw [7]. Materials and Methods The test procedure followed the ASTM 2303 standard, with an initial voltage of 2.0 kV and a constant contaminant flow rate of 0.15 mVmin for four hours [SI. The voltage was increased at a rate of 250Vhour. At the end of the test, the samples were taken from the test bay and the eroded volume was estimated by filling the eroded volume with a soft putty of known density. The weight of the putty was determined using a microbalance and used in the eroded volume calculations. The base rubber (elastomer) used was a two-component room temperature vulcanized (RTV) SIR material which contained no inorganic filler of any type. The filler typelconcentration used is presented in Table 1. Table I: Chemical composition of zyxwv the zyxwv tested samples in IPI test. A PC based data acquisition system, composed of voltage dividers, overvoltage and overcurrent protection circuits, and a 100 IcHz, 16-channel data acquisition card, recorded the source voltage, and voltage and current for each sample. During the test, for every second, four 60 zyxw Hz cycles of data were acquired at a sampling rate of 7580 samples per second. These four cycles were processed by the Fast Fourier Transform (EFT) technique for the leakage current (LC). Then, the LC current data were averaged and smoothed using the moving average technique. The software for analyzing 0-780585845/04/$20.00 m004 I EEE 385