A highly stretchable disulfide-crosslinked epoxidized natural rubber by one-step method

Disulfide bond has unique advantages in the preparation of recyclable rubbers since it not only shows similar sulfur structure to the crosslinks of traditional sulfide rubber systems but also can rearrange and exchange itself under mild external conditions. However, the reported disulfide bond-crosslinked rubbers often exhibit weak tensile strength or poor elongation because of the inappropriate disulfide bond content. Although some disulfide bond incorporated dual-crosslinked rubbers can combine good tensile strength with high elongation, the dual-crosslinked design always requires multi-step chemical modification in the solvent, which is complex and difficult for industrial operation. In this work, aromatic disulfide bonds are introduced into epoxidized natural rubber (ENR) as the vulcanizing agent by a simple one-step method. It is found that the elongation of rubbers can be more than 1100 % with the tensile strength up to 7 MPa when 2.1 phr of 2,2′-dithiosalicylic acid is added. The quantitative relationship between the content of aromatic disulfide bonds and the mechanical properties of ENR is systematically studied, as well as the exchangeable behaviors of disulfide bonds. The research results of this work will not only provide a facile route for preparing rubbers with easily industrial operation and high stretchability, but also contribute to the in-depth understanding of the mechanism of disulfide bonds.