Multiple cross-linked networks enhanced ENR-based composite with excellent self-healing properties

Self-healing property is an excellent feature that can improve the reliability and durability of the materials. In this study, carboxylic multi-walled carbon nanotubes (S-CNTs) and 2,2′-dithiodibenzoic acid (DTSA) were introduced into epoxidized natural rubber (ENR) to prepare a self-healing rubber. S-CNTs and DTSA could react with epoxy groups of ENR to effectively cross-link ENR, in which the cross-linked network consisted of reversible disulfide bonds, β-hydroxyl ester bonds, and hydrogen bonds. The reconfigurable cross-linked network endowed the ENR/S-CNTs/DTSA composites with great self-healing behavior with efficiency up to 99.7%. The multiple cross-linked networks also enhanced the mechanical properties of the composite, whose tensile strength reached more than 400% of the neat ENR. Additionally, optical microscope and scanning electron microscopy disclosed the evolution of the damaged area during the self-healing process, and the crack could be completely repaired after the healing process. This work provides an effective and concise method to prepare self-healing ENR-based elastomer, and it may expand the research scope of self-healing materials.