The effects of γ-radiation on the thermal, mechanical, and segmental dynamics of a silica filled, room temperature vulcanized polysiloxane rubber

RTV-5370 is a filled polydimethylsilxoane-polymethylphenylsiloxane copolymer system originally developed by Dow Coming and now supplied by Rhone Poulenc. There is a desire to develop lifetime assessments of this material for certification programs and as a model system for understanding other filled siloxane polymer systems. We have initiated aging studies on these materials by employing accelerated aging tests with exposure to Co-60 gamma-radiation. The effects of radiation exposure have been investigated by thermal (differential scanning calorimetry), mechanical (dynamic mechanical analysis), chemical (solvent swelling), and segmental dynamics (nuclear magnetic resonance) methods. The data show that RTV-5370 undergoes predominately radiation-induced crosslinking reactions over the dose range investigated. These reactions reduce the molecular weight between crosslinks, thereby hardening the composite and reducing the motional dynamics of segmental motion. DSC studies show dose dependent crystallization phenomena. Published by Elsevier Science Ltd.