Oxidative degradation aging mechanism

Estane/NP binder was aged under inert atmosphere at 65, 75 and 85°C for the oxidative degradation study. These samples were analyzed by H NMR and GPC analysis. The first order kinetics was examined based on the relative amount of oxidation in Estane. Mechanical properties of this aged binder were examined and were correlated to the amount of Estane oxidation. 

Oxidative degradation dominates when Estane/NP is thermally aged in the absence of water and oxygen. Through NMR analysis, the oxidation of the bridging methylene group was quantified. These data contributed to the development of kinetic models for prediction of oxidative degradation. We observed a correlation between oxidation and mechanical properties. 

In addition, oxidative degradation related to poor consolidation has been found in both in vivo and shelf-aged prostheses that were either gamma sterilized or ethylene oxide gas (EtO) sterilized (Costa et al. 2002). When oxidation related to consolidation occurs, the oxidation profile through the cups section is inhomogeneous and the maximum oxidation is observed near the center of the prosthesis. It is worth mentioning that this consolidation-related oxidation mechanism is often accompanied by whitening of the material, visible to the naked eye. 

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