Molecular mobility of crosslinked elastomers stretched above Tg

A uniaxial deformation is performed on a styrene–butadiene elastomer and two nitril butadiene elastomers with two different crosslinking densities in their rubbery state. The slow α-relaxation process is investigated under constant deformation using low frequency dynamic mechanical analysis. No effect is observed in the stretched elastomers although microstructural changes are detected thanks to tensile tests and wide angle X-ray scattering experiments. A possible explanation of these results is that the inter-molecular interactions are not significantly modified in the stretched network.