Fabrication of Ultraviolet Aging Chamber and Testing of Polymeric Insulators /

Abstract

Epoxy and its composites have expressed exceptional qualities for usage in high-voltage outdoor insulation applications. However, the organic structure of epoxy based insulators is deteriorated due to UV-A radiations in the outdoor environment. By fabricating three sample compositions consisting of pristine epoxy (NEP), 15 weight percent epoxy microcomposite (EPMC), and 5 weight percent epoxy nanocomposite EPNC, the influence of UV radiations on the physiochemical properties of epoxy was studied. An ultraviolet aging chamber was fabricated to conduct the aging of prepared samples. Inside the chamber, 5mW/cm intensity of UV-A radiations was maintained. The performance of the samples was analyzed with visual inspection, hydrophobicity classification by the Swedish Transmission Research Institute’s (STRI) hydrophobicity classification, Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FTIR) spectroscopy. Physiochemical degradations were observed in the samples due to severe oxidation which resulted in the formation of ester and carbonyl groups on the surface of the samples. Color changes were observed due to surface oxidation. Hydrophobicity of all the samples was degraded with neat epoxy, EPMC and EPNC expressing HC-3, HC-3 and HC-2 classes after 1000 hours of aging. SEM micrographs expressed holes and loss of material. Filler exposure was also seen in micrographs however degree of filler exposure was less in case of nanocomposite. Statistical analysis of results of FTIR expressed decrease in absorption peaks of hydrophobic methyl groups due to chain scission which consequently resulted in increment of carbonyl and ester groups’ absorption peaks. For NEP, EPMC, and EPNC, the FTIR peaks of carbonyl group at 1726 expressed an increase of 158 percent, 75.86 percent, and 33.33 percent, respectively. Similarly C=C stretching at ~1606.52 increased by 56 percent, 37.25 percent and 5.12 percent for NEP, EPMC and EPNC, respectively. This demonstrates that EPNC outperformed EPMC and NEP in terms of resistance against surface oxidation. Fillers improved the chain integrity of the polymer, whereas nano fillers performed significantly better due to their larger surface area and surface energy.