Deformation and failure mechanisms of natural/waste rubber blends under mechanical and thermal cycles: a synchrotron in situ study

Abstract

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.

The authors acknowledge the group eb-POLICOM: Polímers i Compòsits Ecològics i Biodegradables, a research group of the Generalitat de Catalunya (Grant 2021 SGR 01042). These experiments were performed at BL11-NCD-SWEET beamline at ALBA Synchrotron with the collaboration of ALBA staff, Marc Malfois, and Cristian Huck Iriart. We acknowledge the project EcoPolyRub PID2023-151338NB-I00 funded by the Ministerio de Ciencia, Innovación y Universidades (MICIU), the Agencia Estatal de Investigación (AEI), and the FEDER funds. This work is part of María de Maeztu Units of Excellence Programme CEX2023-001300-M / funded by MICIU/AEI /10.13039/501100011033. The authors acknowledge the project RubNatCell from the ERASMUS SEED FUNDING UNITE program cofounded by the European Union.

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Postprint (published version)