Enhanced Properties of Sulfur‐Vulcanized Natural Rubber via Post‐Cure‐Induced Polymerization of Bismaleimide

ABSTRACT This work demonstrates a novel approach to utilize a minor network damage due to reversion in a natural rubber (NR)/accelerated‐sulfur system by incorporating a thermally polymerizable bismaleimide, Perkalink 900 (PL), as a reactive modifier. For that, a blend of NR/PL: 90/10 is prepared and crosslinks the rubber phase using a conventional vulcanization (CV) system. The curing time is extended to 2 h to facilitate two key processes: (i) the Diels‐Alder reaction between the in situ formed diene‐backed NR at the point of reversion and PL, and (ii) thermal polymerization of PL within the damaged network. The 2 h cured NR/PL: 90/10 composition at 160°C exhibits exceptionally enhanced mechanical properties—including tensile strength, modulus, hardness, crosslink density, and compression set—compared to the unmodified (NR/PL:100/0) counterpart. A plausible chemical mechanism is proposed to explain the observed improvements, highlighting the effective integration of PL into the NR matrix in the post‐curing phase.