Non-Arrhenius behavior for oxidative degradation of chlorosulfonated polyethylene materials

We have carried out oven aging studies on eight different commercial chlorosulfonated polyethylene cable jacket materials at temperatures ranging from 80degreesC to 150degreesC utilizing ultimate tensile elongation as the degradation parameter. For each material, the elongation results were time-temperature superposed at the lowest aging temperature. When the resulting empirical shift factors were tested for Arrhenius behavior, it was found that the eight materials were Arrhenius at similar to100degreesC and higher with very similar activation energies averaging similar to107 kJ/mol. Longer-term aging results at temperatures lower than 100degreesC for three of the materials provided evidence for curvature to lower activation energies. For one of these materials, we conducted oxidation rate measurements at six temperatures ranging from 37degreesC to 108degreesC. The results offered further evidence for a small drop in activation energy below 100degreesC. Chemical evidence supporting this change in activation energy was derived from analysis of the production rates of CO2 during oxidation. As the temperature was lowered, the amount of CO2 produced relative to the O-2 consumed dropped substantially, implying that the chemistry leading to CO2 becomes less important at lower temperatures. (C) 2004 Elsevier Ltd. All rights reserved.