Search

This thesis presents a laboratory study on the aging mechanisms responsible for loss and recovery of hydrophobicity of high temperature vulcanized silicone rubber used as a high voltage insulator. The effects of different stresses of heat and water salinity on the hydrophobicity were determined as a function of time, by measuring intermittently the static contact angle, the weight and average surface roughness during aging as well as recovery. The SEM, EDS and ATR-FTIR spectroscopy were utilized to study the physical and chemical changes on the surface. In addition, the surface free energies γ s, γsl and W sl of the specimens were calculated from the measured data of the contact angles of &thetas;W and &thetas;MI. The loss and recovery of hydrophobicity of the specimens due to migration of the low molecular weight (LMW) fluid from bulk to the surface under different stress conditions was investigated. The contents of the extracted LMW fluid were characterized by mass spectrometry, IR and NMR spectroscopy.