Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: Part I-contact angle and surface chemical properties

The effects of liquids immersion and subsequent drying on the surface properties of filled high temperature vulcanized (HTV) silicone rubber have been reported in this series of paper. In this first paper, the surface hydrophobicity characterized by static contact angle and surface chemical properties characterized by a comprehensive analysis of Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and thermal desorption gas chromatography mass spectrometry (TD-GC/MS) have been studied. The liquids employed in this study were deionized water, NaCl solution and nitric acid solution, which represented the actual liquids that composite insulators could encounter in practice use. As for the NaCl solution, the lower the concentration, the greater its impact on the hydrophobicity of the silicone rubber (the deionized water can be considered as the NaCl solution of concentration of 0 mol/L). As for the nitric acid solution, the higher the concentration, the greater its impact on the hydrophobicity of silicone rubber. During the permeation process of deionized water and NaCl solution into HTV silicone rubber, some Alumina Tri-hydrate (ATH) filler and low molecular weight (LMW) could be dissolved into the liquids. Nitric acid solution not only dissolved the ATH filler, but also interacted with the ATH filler and degraded the polymer matrix.