The mechanisms of hydrophobic recovery of polydimethylsiloxane elastomers exposed to partial electrical discharges

Silicone elastomers exposed to electrical discharges can be rendered hydrophilic, and the loss of water repellency is related to the energy level and number of the discharge pulses on the surface. However, the silicone surface has the unique ability to recover the hydrophobicity and enhance the performance of a polymer insulator. Most of the studies of the loss and recovery of hydrophobicity on elastomer surfaces have been carried out at high discharge energies experienced under severe service conditions. Despite numerous studies, the mechanisms contributing to the loss and recovery of hydrophobicity under lower energy partial discharges are not fully elucidated. The current study was done with partial discharge pulses in the range 10-10000 pC and by using a needle-to-plane electrode configuration. At very low levels of energy pulses, the recovery is primarily caused by the migration of preexisting fluids from the bulk to the surface of the elastomer. At higher levels of partial discharges, the fluids no longer play the same role, but the dominant mechanism in the recovery becomes the migration of in situ produced low molecular weight (LMW) species in the elastomer. These studies were done under dry and wet conditions. (C) 2001 Academic Press.