Hydrophobic recovery of polydimethylsiloxane elastomer exposed to partial electrical discharge

The hydrophobic recovery of polydimethylsiloxane elastomers was studied aft er exposure to partial electrical discharge. Silicone elastomers that were thoroughly extracted of free oligomeric impurities as well as those deliber ately contaminated with low molecular weight (LMW) silicone fluids were use d for these studies. Contact angle and X-ray photoelectron spectroscopy rev ealed that the recovery rates of the oxidized extracted samples are strongl y influenced by the applied voltage, humidity, and aging condition. The rec overy rates increase considerably as the applied voltage and the humidity d uring discharge increase. Remarkably, the oxidized samples stored under hig h vacuum (10(-7) Torr) exhibit lower recovery rates than those aged in air. Free silicone fluid, when added to the elastomer, affects the recovery rat e as well; however, significant recovery is seen even without any added flu id. These results imply that the LMW species that are formed in situ during electrical discharge are sufficient to cause the hydrophobic recovery of o xidized PDMS elastomers. (C) 2000 Academic Press.