Enhancing the dispersion and adhesion of short aramid fibers in bromo‐isobutylene‐isoprene rubber using maleated polybutadiene resin via co‐vulcanization with 4, 4’ bis(maleimido)diphenylmethane

Composites based on brominated isobutylene‐isoprene rubber (BIIR) and 5‐mm short aramid fiber were prepared by varying the fiber content from 1 to 10 phr using 4, 4’ bismaleimido diphenyl methane (BMDM) and zinc oxide as the vulcanizing agent. Morphological analysis revealed that the fiber dispersion becomes inferior even at 5 phr loading due to fibrillation during mixing. As a result, the 10 phr fiber‐filled composite showed a brittle failure under a tensile deformation. To solve this problem, maleic anhydride‐grafted polybutadiene (MA‐g‐PB) resin was treated with the aramid fibers in the 1:1 ratio prior to mixing with the rubber matrix. Excellent fiber dispersion could be seen in both the visual image of the molded sheet and the scanning electron microscope image of the fractured surface. The stress–strain curve of the 10 phr fiber‐filled composite after the resin treatment showed a tough deformation behavior with a breaking elongation >100% indicating an enhanced fiber‐matrix adhesion. From the vulcanization studies of the fiber‐filled BIIR before and after the MA‐g‐PB resin treatment, it has been identified that a co‐crosslinking reaction between the MA‐g‐PB‐treated fiber and the BIIR matrix with BMDM via Alder‐ene and Diels‐Alder reactions is responsible for the enhanced fiber–matrix adhesion. POLYM. COMPOS., 40:2993–3004, 2019. © 2018 Society of Plastics Engineers