Characteristic change of sealing rubber due to usage time

Gas insulated switchgear (GIS) is a compact metal encapsulated switchgear consisting of high-voltage components such as circuit-breakers and disconnectors, which can be safely set up in confined spaces. However, some GISs have been used for more than 40 years, so characteristic of sealing rubber is considered to be degraded. We find possibility of aging of the sealing rubber by comparing surface characteristics of an aging sealing rubber and that of a new one. We used three methods to analyze the characteristics of aged sealing rubber and that of a new one. The methods we used are SEM-EDX analysis, FTIR spectroscopy and tensile test. From the SEM-EDX analysis, we found that the unevenness appeared on the surface of aging one as the filler of the rubber material may appear on the surface. From the FTIR spectroscopy, we found that a new peak appears at wave number 1050 nm, 1250 nm and 1750 nm so we consider that 1050 nm and 1250 nm are a bond of C-O, so oxidative deterioration is proceeding possibly. And the peak near the wavenumber 1750 is disappeared for aged sample of No.46. Since the peak near wave number 1750 shows a double bond, there is a possibility that the double bond was cleaved by the addition reaction. From the tensile test, we found that the aging one is breaking with a smaller strain than the new one but the slope of the graph (Young's modulus) is approximately equal, so we consider that tensile stress leading to breaking of aged one is smaller than that of new one but the elastic force of the sealing rubber has not changed greatly since the Young's modulus is approximately equal. Therefore, although the surface is oxidized probably, we found that there is little influence on the gas sealing performance since the elastic force of the sealing rubber is not decreased so much.