PROJECT TITLE :
Aging characterization of high temperature vulcanized silicone rubber housing material used for outdoor insulation
During the sphere service of composite insulators, high temperature vulcanized (HTV) silicone rubber (SIR) material used for insulator's sheath and sheds is gradually aging, and so the way to effectively evaluate its aging state has become an inevitable issue. In this paper, artificially corona-aged and naturally web site-aged SIR materials are used as samples, and their properties such as hydrophobicity, leakage current, trap density/energy level, surface microstructure and chemical composition are investigated for comparative study. With the increasing of corona aging intensity, the contact angle of SIR samples drops gradually and recovers more slowly. The hydrophobicity of web site-aged insulators conjointly declines, from HC1 for 2-year service to HC5 for fifteen-year service. The leakage current of corona-aged and website-aged samples each increase with aging, that indicates that aging induces the increase of surface conductivity of SIR material. The peak trap density of corona-aged and web site-aged samples increases with the aging length or service period remarkably. The changes of these properties are attributed to the changes of micro-structures and compositions in the surface layer of SIR. The scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) analysis results mirror that a hardened inorganic silica-like (SiO2) layer with many polar chemical groups and distributed micro-pores is made on the surface of SIR material after corona aging. As a result of of this silica-like layer, the hydrophobicity decreases while surface conductivity and entice density of SIR material will increase. Besides the ancient properties like hydrophobicity and surface conductivity, the lure density is predicted to be a completely unique parameter for effective evaluation of aging state of HTV silicone rubber material.
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