Achieving Modulus Matching and Enhanced Fatigue Resistance in Chloroprene Rubber/Trans-1, 4-poly(isoprene-co-butadiene) Nanocomposites: A Study on the Balance Between Crosslinking and Crystallinity in Dispersed Domains

Improving the fatigue resistance and service life of chloroprene rubber (CR) nanocomposites through cost-effective rubber blending technology is a highly desirable goal for both academic research and industrial applications. However, critical challenges remain, particularly in optimizing the structure of the secondary component within CR matrix, which significantly affects mechanical durability. In this study, the incorporation of trans-1,4-poly(isoprene-co-butadiene) (TBIR) as a secondary component with CR was explored to produce CR/TBIR (90/10) vulcanizates with different TBIR domain structures, achieved by varying sulfur content. The results demonstrated that increasing sulfur content significantly enhanced crosslinking density in TBIR domains with a high proportion of disulfidic and polysulfidic bonds, and reduced TBIR crystallinity. Additionally, filler dispersion was significantly improved. At an optimal sulfur content (1.0 phr), the CR/TBIR-1.0 vulcanizate achieved an optimized TBIR domain structure with balanced crosslinking and crystallinity, leading to improved modulus matching between CR and TBIR domains. This resulted in superior mechanical properties, including enhanced tensile strength, elongation at break, abrasion resistance, and greatly improved tensile fatigue life, with damping properties remaining almost unchanged compared to CR vulcanizate. The optimized TBIR domains exhibited synergistic effects from adequate crosslinking density, moderate crystallinity, and improved filler dispersion through the whole matrix, facilitating modulus matching for superior stress transfer, inhibited crack initiation and enhanced fatigue resistance. Compared with conventional CR-based rubber blends, this study provides a novel structural optimization strategy, demonstrating that precisely tuning crosslinking density and crystallinity of TBIR domains offers a promising route to develop durable, high-performance elastomeric damping nanocomposites.