Strain Softening of Bimodal Isoprene Rubber Vulcanizates

Isoprene rubber (IR) vulcanizates soften upon large-amplitude oscillational shear and large-strain cyclic tensile deformation. The mechanisms of these two strain softening behaviors remain unclarified and methods for reducing the accompanied mechanical dissipations are not well established. Herein IR/liquid isoprene rubber bimodal blends are cured into vulcanizates with similar cross-linking densities. The results indicate that, in comparison with the pure IR network, the bimodal networks demonstrate lowered loss modulus and loss tangent at low strain amplitudes during oscillational shear and reduced loading-unloading dissipation energy at large strains during cyclic tensile deformation. The latter is ascribed to the weakened strain-induced crystallization (SIC) as disclosed by in situ wide angle X-ray diffraction. To the best of the current knowledge, the depression of SIC and thus dissipation energy in cyclic deformation is seldom reported for rubber materials. This work provides a new perspective for preparing rubber materials with balanced deformation resistance and mechanical hysteresis.

Automated summary

This study examines the vulcanizates of IR/liquid isoprene rubber bimodal blends and finds that compared to pure IR networks, bimodal networks exhibit lower loss modulus and loss tangent during oscillational shear at low strain amplitudes, as well as reduced loading-unloading dissipation energy during cyclic tensile deformation at large strains, attributed to the weakened strain-induced crystallization (SIC). This work offers a new perspective for preparing rubber materials with balanced deformation resistance and mechanical hysteresis.