Effect of combined gamma and neutron irradiation on EPDM and FPM elastomers

The effect of mixed gamma and neutron radiation on the properties of O-rings made of elastomeric materials differing for composition and declared radiation resistance, a fluoroelastomer and an ethylene-propylene diene rubber, was investigated experimentally. The O-rings were subject to mixed gamma and neutron irradiation for various hours, leading to significant changes in the mechanical behaviour. These variations were further explored with tests that allowed highlighting the changes in the macromolecular architecture: solvent swelling tests, to evaluate the occurrence of two competitive phenomena of crosslinking and cleavage, and dynamic mechanical thermal analysis, to better interpret the mechanical response as due to the evolution of the crosslinked structure and of the temperature dependence.