Cystamine Coupling Agent-Modified Waste Tire-Derived Pyrolysis Carbon Black as a High-Performance Rubber-Reinforcing Filler

Abstract As a bulk solid waste, the reuse of waste tire-derived pyrolysis carbon black (CBp) as a rubber reinforcing filler is vital for resource recycling and environmental protection. However, compared with commercial carbon black, its high ash content, low surface activity, and poor reinforcing performance limit its practical application. Herein, we propose a novel coupling agent─cystamine (SN)─to enhance the interfacial forces between deashed pyrolysis carbon black (CBpf) and natural rubber (NR) molecules. The amino groups of SN react with oxygen-containing functional groups on the carbon black surface, while disulfide bonds cross-link with rubber chains, creating a molecular bridge between CBpf and NR. The results show that CBpf-5SN/NR exhibits the optimal stress at 300% elongation, with the stress at 300% elongation increasing from 8.1 to 14.5 MPa, outperforming that of N660/NR (12.7 MPa). Furthermore, the loss factor tan δ decreases to 0.033, the cross-link density rises from 0.27 mmol·cm–3 to 0.43 mmol·cm–3, and the bound rubber content increases from 30.26% to 54.46%. This study provides a new, promising coupling strategy for the high-value utilization of CBp with enhanced mechanical performance.