Evaluation of surface degradation of silicone rubber using gas chromatography/mass spectroscopy

Abstract

Analysis using Gas Chromatography/Mass Spectroscopy (GC/MS) was performed for evaluation of surface degradation of silicone insulating materials. Silicones are used as coatings for porcelain insulators and shed material for high voltage composite insulators. A comparison between virgin silicone rubber and aged silicone rubber samples, which were aged either on actual power lines or during a field exposure test, was made by GC/MS analysis. The GC/MS spectrum of siloxane in silicone rubber has a series of peaks which corresponds to the number of dimethylsiloxane units in the molecule. We found that the aged samples had a larger concentration of low molecular weight siloxane species than the virgin samples. The top shed surfaces generated more low molecular weight siloxane species than the bottom shed surfaces. Since GC/MS analysis can determine the molecular weight distribution of polymer insulating materials, evaluation of the degree of surface degradation and estimation of the remaining life of insulators may be possible.

Effects of electric partial discharges on the rheological and chemical properties of polymers used in HV composite insulators after railway service

“…Additionally, it is impossible to generalize the experimental observations without clarifying the exact nature of the silicone studied and its physical state (prepolymer or crosslinked). In the framework of this study, the results obtained are consistent with the experimental data obtained by Homma et al on both RTV and HTV silicones [47,48]. Using gas chromatography/mass spectrometry (GC-MS) technique, the authors clearly demonstrated that field aged silicones suffered from depolymerization and oxidation when they are used in HV equipments.…”

Surface Modification of Silicone Rubber After Corona Exposure

“…The column temperature was varied from 35 to 300 °C at 15 °C · min −1 . Then, the output from the GC column was passed to an MS for chemical identification and quantification of the volatile components 23. Figure 9 shows the profile of GC for virgin and corona‐aged samples.…”

Effect of aluminum hydroxide on low‐molecular‐weight siloxane distribution and microstructure of high‐temperature vulcanized silicone rubber

“…This result was further verified by observing the retention time using the standard D 4 . Usually, successive peaks in the gas chromatogram correspond to a unit increase in the number of dimethylsiloxane units . Peaks appearing at 8.70, 10.39, 11.88, 13.20, 14.32, 15.32, 16.23, 17.06, 17.82, 18.53, 19.20, 19.95, 20.82, 21.87, 23.17, and 24.83 min have been assigned to cyclic dimethylsiloxane oligomers (from D5 to D20, respectively) by GC–MS.…”