A mechanistic analysis of the crack initiation and growth in rubbers composites containing sustainable thermoplastic elastomers

• Evaluating the window of experimental procedures to incorporate TPE into rubbers • Outstanding flex cracking resistance for a NR/SBS system due to viscoelasticity • Reporting a change of crack growth from smooth to knotty tearing for SBR/SBS • Detecting signs of TPE-induced mobility augmentation for NR chains containing silica • Reporting a better suitability of SBR, compared to NR, to be reinforced by the TPE Recycling challenges in rubber have driven research into recyclable thermoplastic elastomers (TPEs) to extend the life cycle of conventional rubbers. This study investigates the impact of Styrene-Butadiene-Styrene (SBS) TPEs on the crack growth behavior of silica-reinforced NR and SBR rubber compounds. Crack growth analyses, including trouser tearing, fatigue flex cracking resistance, and tearing patterns, were conducted alongside morphological and viscoelastic non-linear tests to establish a mechanistic understanding. Results revealed a critical TPE loading level at which crack growth behavior improves. NR exhibited enhanced crack resistance at low TPE content, with 20 phr SBS providing exceptional fatigue resistance—showing no cracking damage even after 100,000 dynamic loading cycles. This improvement was attributed to enhanced silica dispersion which creates stronger filler-polymer interactions, increased energy dissipation in the interphase layer, and physical barriers to crack propagation. However, excessive TPE in NR led to property deterioration due to increased chain mobility. For SBR, crack growth resistance improved with higher SBS content, particularly at 40 phr. These findings highlight the potential of TPEs in sustainable engineering applications by optimizing crack resistance in rubber composites.