Dual Cross-Linked Self-Healing and Recyclable Epoxidized Natural Rubber Based on Multiple Reversible Effects

Generally, self-healing research based on commercial rubber is of great significance in sustainable development by extending the lifetime of materials. However, it is still a great challenge so far to prepare recyclable rubber that combine excellent self-healing properties with good mechanical strength and is also recyclable. Herein, we report the use of epoxidized natural rubber (ENR), a reactive polymer presenting dual functional groups (unsaturated double bonds and epoxy sites) available for cross-linking, to prepare a dual cross-linked self-healing ENR based on dynamic disulfide metathesis and thermoreversible hydrogen bonding. Specifically, different structures of aromatic disulfide compounds are introduced into the same system to promote the disulfide metathesis and thus improving the self-healing efficiency of the material. As a result, the dual cross-linked ENR shows high mechanical strength (9.3 ± 0.3 MPa), high self-healing efficiency (up to 98%), and ideal recyclability. In addition, cyclic fatigue tensile test shows that the self-healing properties of the present material are not affected by the damage forms, whether it is complete fracture or cyclic fatigue damage. These outcomes are expected to promote the development of self-healing technology in the sustainable application of cross-linked rubber materials.