Silicone rubber (SIR) shows superior performance when used outdoors

but its surface can be transformed frominherently hydrophobic to hydrophilic by the adsorption of contaminants. Al(OH)3

Al2O3

quartz powder and active carbonwere selected as authentic contaminants. Hydrophobicity of the surface was determined using contact angle measurement.The results indicate that the adsorbability of the contaminants can strongly affect the hydrophobicity of contaminated SIR surface. The incrrasing rate of contact angle of specimens contaminated by Al(OH)3 was much faster than that by Al2O3 and quartz due to the adsorption of migrated low molecular weight (LMW) polydimethylsiloxanes.Specimens contaminated by active carbon could achieve surface hydrophobicity within 15 min because active carbon has high adsorbability.Surfaces of contaminated ultrapure SIR

polytetrafluoroethylene(PTFE) and glass remain hydrophilic because they contain no mobile LMW components.The addition of oligomeric polydimethylsiloxanes has little effect on the hydrophobicity of contaminants covered on SIR surface.