Evolution of EPDM networks aged by gamma irradiation - Consequences on the mechanical properties

Different Ethylene-Propylene Diene Monomer (EPDM) elastomers with different crosslink densities have been processed in order to evaluate the influence of gamma irradiation on their properties. In the case of a major phenomenon of chain scissions, the consequences are a decrease in the modulus and also a decrease in the strain at break. This decrease in the strain at break is opposite to what is expected for materials with increasing average chain length between crosslinks. To gain more insight into the network architecture, which is presumed to be responsible for this behavior, Charlesby's approach is applied. In tandem, a computational model of the degradation is developed for improved prediction of the evolution of the elastic modulus. Using these calculations, a novel interpretation of the ultimate properties of the elastomer as a function of its architecture is proposed. (C) 2009 Elsevier Ltd. All rights reserved.