Thermal ageing assessment of EPDM-chlorosulfonated polyethylene insulated cables using line resonance analysis (LIRA)

Two cables with chlorosulfonated polyethylene jackets and EPDM core insulations, but having different designs and geometries, were aged at 140 degrees C for different periods of time mimicking ageing at 50 degrees C for an exposure time of more than one hundred years. The cable samples were aged in dry air and dry nitrogen. The cable samples were studied with indenter modulus measurements, tensile tests, infrared spectroscopy and line resonance analysis (LIRA). The main question was whether universal correlations could be established between the two classical methods (indenter and tensile testing) and LIRA. The global ageing indicator (CBAC2) obtained by LIRA showed good correlation with the indenter modulus of the jacketing and with the mechanical properties of the core insulation. Almost universal CBAC2 values were obtained for samples reaching a critical state; the latter being defined according to a criterion based on LOCA test data. Infrared spectroscopy showed that the core insulation degraded by an essentially oxygen-free mechanism, with a gradual increase in the concentration of vinyl and vinylene groups. (C) 2010 Elsevier Ltd. All rights reserved.