Estudo da fotodegradação de borracha de silicone utilizada em isoladores para rede elétrica

Abstract

The combination of properties provided by the silicone rubber (SR) makes this material widely used in the energy sector, especially in manufacturing insulators for transmission and distribution lines, replacing porcelain and glass materials. Mechanical and thermal resistance in conjunction with high insulating capacity and hydrophobic surface characterize the performance of this elastomers class. Such equipment must maintain the properties over time of use, remembering that they will be subjected to multiple requests as: solar radiation, humidity, temperature cycles and pollution, which directly affect the lifespan of the polymeric material and may lead to failure in the power supply. Therefore, this work evaluated the photodegradation of SR coating applied in insulators on electric grid. For this, there was the extraction of low molecular weight (LMW) polymer chains of the samples with toluene. Samples without prior extraction together with the samples with solvent extraction, they were subjected to aging in an artificial weathering chamber Weather-Ometer, for 2000 hours. It evaluated the effect of aging by making withdrawals every 500 hours, monitored to hydrophobicity, hardness, LMW chains extracted content and chemical changes by energy dispersive spectroscopy (EDS). The results showed that after aging there was a reduction in the percentage of LMW chains extracted, which may be attributed to leaching of LMW compounds during the test. Slight increase was observed in the content of LMW chains in the samples that had been subjected to extraction and recovery of hydrophobicity to a certain aging period, which can be attributed to the breaking of the chains during photodegradation and/or migration of residual LMW chains. The hardness of the samples increased during aging, indicating the occurrence of crosslinking process between chains concurrently with the breaking mechanisms. The results obtained by EDS reinforce this statement, they showed a tendency of reduction of carbon content and increased the oxygen content in the course of aging.