Deformation and Failure Mechanisms of Natural/Waste Rubber Blends Under Mechanical and Thermal Cycles: A Synchrotron In Situ Study

This study investigates the deformation and failure mechanisms of natural rubber (NR) and waste rubber blends under mechanical and thermal cycles using in situ synchrotron wide-angle X-ray diffraction (WAXD). The incorporation of ground tire rubber (GTR) into NR enhances strain-induced crystallization (SIC), reducing the onset strain for crystallization and increasing mechanical reinforcement. Cyclic loadings reveal significant hysteresis and residual deformation, influenced by GTR content. Moreover, the strain at complete melting of SIC crystals is found to decrease with GTR content, suggesting a higher stability of SIC crystals. Under combined tensile stress and high temperature, NR/GTR blends exhibit failure likely due to decohesion at the NR/GTR interface and growth of cavities in the NR matrix. Nonetheless, the temperature at fracture is increased by 15°C with the GTR content at a strain of 300%. As SIC crystals promote resistance to crack growth, failure is delayed under high stress and temperature owing to the nucleating effect of GTR on SIC. In spite of the limitations imposed by the interface between NR and GTR, the study highlights the role of GTR in the promotion of SIC in reinforcing NR-based composites.