Sulfur Co-polymer as a universal adhesive to construct segregated structure in cross-linked rubber toward improved conductive and mechanical properties

Abstract

Creating segregated structure within composites can significantly improve electrical conductivity but usually compromises mechanical properties. In this contribution, we introduced a straightforward and universal method to fabricate segregated rubber composites with a rare integration of high electrical conductivity and mechanical robustness by utilizing an inverse vulcanized copolymer (SP) as an adhesive to bind the segregated domains. Specifically, sulfur-crosslinked butadiene styrene rubber (SBR) granules were mixed with SP and carbon nanotubes (CNTs), followed by compression molding. CNTs embedded within SP are strategically dispersed along the boundaries of SBR granules, and the reaction of SP with SBR granules creates covalent bonding among the segregated domains and increases their crosslinking density. The segregated skeleton constituted by highly interconnected CNTs is robust, which imparts the composites with high electrical conductivity that is stable upon deformations and is able to heal after damage. In addition, the rigid segregated skeleton preferentially ruptures to dissipate enormous energy, and the cohesive interphase facilitates chain finite extensibility in the highly crosslinked segregated domains, resulting in remarkable enhancements on the tensile strength and modulus of the composites. The universality of this strategy is further demonstrated by using ground waste tyre rubber as matrix and boron nitride sheets as filler.