Dynamic Ionic Crosslinking of Epoxidized Natural Rubber for Rebonding and Reprocessable Carbon Black–Reinforced SBR/BR Composites

Abstract

This study presents a dynamic ionic crosslinking strategy for developing self-healing and reprocessable elastomeric composites based on epoxidized natural rubber (ENR) containing 50 mol% epoxide which was chemically modified with imidazole (IM) to generate reversible ionic interactions and used as a functional modifier in carbon black (CB)-filled styrene–butadiene rubber (SBR)/butadiene rubber (BR) blends commonly applied in tire and general rubber products. The imidazole-modified ENR (mE50) introduces dynamic imidazolium–epoxy ionic crosslinks that enable autonomous self-healing, while CB reinforcement provides mechanical strength, thermal stability, and efficient stress transfer. The compounding sequence is critical, as preferential adsorption of SBR/BR onto CB surfaces optimizes rubber–filler interactions without compromising the healing capability of the ENR phase. Mechanical, dynamic mechanical, temperature scanning stress relaxation (TSSR), and reprocessing evaluations demonstrate that optimized mE50–CB composites exhibit a tensile strength of ∼10 MPa, elongation at break above 400%, and self-healing efficiency exceeding 100% based on modulus recovery, together with good reprocessability after damage. The synergistic combination of dynamic ionic networks and well-dispersed CB enhances energy dissipation, molecular mobility, and stress redistribution. This work establishes ionically crosslinked ENR as an effective modifier for improving durability, healing efficiency, and recyclability in CB-filled composites, offering a viable pathway toward sustainable high-performance elastomers.