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Effects of heating on the presence of fluid in EPDM

One of the important properties of ethylene propylene diene monomer (EPDM) is its inherent low surface energy which inhibits the spread of water on the surface even in the presence of pollution. This reduces the development of leakage current and flashover. The water repellency (hydrophobicity) of the surface is maintained as a result of diffusion of low molecular weight (LMW) fluid from the bulk to the surface. A study of the generation and the loss of the LMW fluid in EPDM has been conducted as a function of temperature in order to simulate the effects of the heat of the dry band discharges on the surface. The amount of LMW fluid on the surface and in the bulk of the material determines the maintenance of the hydrophobicity during the lifetime of the EPDM material used as insulators. In this paper, the generation and the loss of LMW fluid in EPDM is determined after subjecting the specimens to different combinations of temperatures and durations of heating. The contact angle of EPDM is determined before and after different heat treatments and is correlated to the presence of the fluid. The temperature is varied from 23 to 380/spl deg/C and the duration of heating from 1 to 11 h. The fluid within the EPDM is extracted using analytical hexane. The effect on the decomposition of the alumina trihydrate filler at different temperatures is also studied. The fluid is identified using a Nuclear Magnetic Resonance (NMR) techniques.