Characterization of radiation-induced aging in silica-reinforced polysiloxane composites

Changes in crosslink density and chemical structure of silica-reinforced si licone polymer composites due to aging in gamma radiation environments were examined in this study. Solvent swelling was utilized to determine the ind ividual contributions of the matrix polymer and filler phase to the overall crosslink density of silica-reinforced silicone polymer composites. The re sults show how polymer-filler hydrogen bonding dominates the overall crossl ink density of the material. Air-irradiated samples displayed decreased hyd rogen bonding at the polymer-filler interface, while vacuum irradiation rev ealed the opposite effect. These results were supported by solid-state NMR experiments that correlated the motional dynamics of the polymer chains wit h crosslink density through T-2 relaxation time measurements. GC/MS analysi s was used to identify degradation products formed as a result of irradiati on and speculate upon likely degradation mechanisms. Published by Elsevier Science Ltd.