Effects of heating on the generation of fluid in an alloy of EPDM/SIR

Ethylene propylene diene monomer (EPDM), silicone rubber (SIR) and their alloys have good performance when used as outdoor insulators. The hydrophobicity of the surface is maintained in wet conditions as a result of diffusion of low molecular weight (LMW) fluid from the bulk to the surface. The amount of LMW fluid on the surface and in the bulk of the material determines the hydrophobicity during the lifetime of the alloy of EPDM/SIR used as insulators. A study of the amount, loss and generation of the LMW fluid in an alloy of EPDM/SIR used for outdoor insulators has been performed as a function of temperature in order to simulate the effects of the heat of the dry band arcings on the surface. In this alloy, the highest amount of LMW fluid is determined to be 7wt% by extraction in hexane. The loss of LMW fluid is also determined after subjecting the specimens to different combinations of temperatures and durations of heating. The temperature is varied from 23 to 300°C and the duration of heating from 0.5 to 32 h. The effect on the decomposition of the alumina trihydrate filler is also studied.