Characteristics of powdered layer on silicone rubber surface

Abstract

In recent years, varying degrees of surface pulverization had been found on composite insulators running for years in severe outdoor environment such as dry, high altitude, salt fog and intensive ultraviolet radiation. Research on the basic characteristics of powdered substance is essential to maintain a high reliability of the power grid. In this study, the characteristics of the powdered layer of the composite insulator sheds aged for more than 10 years under three different environmental stresses are analyzed. The results show that powdered substance of each composite insulator sample contains two parts: the organic silicon which is oxidative degradation product of the original material polydimethylsiloxane (PDMS), and the partially dehydrated and deteriorated flame retardant filler aluminum hydroxide (ATH). However, the thickness of the powdered layer, the particle size distribution of the powdered substance and the composition ratio between the two components are different. The average particle size of powdered substance is between 2–7 μm. The content of Al element is 31.8–34.5%, the content of Si element is 12.7–17.5%, and the mass fraction ratio of two types of powdered substance is about 1/2–1/3. The essence of pulverization is finally concluded that the composite insulator is severely oxidized and degraded under the effect of various aging factors. The organic component silicone rubber is decomposed to fragments, and the bonding between inorganic flame retardant filler and polymer become weak. They will be detached from the main body skeleton and lost partly, then build up at the surface, forming powdered layer.

Keywords

• Silicone rubber
• Pulverization
• Properties test
• Material analysis