Second Natural Rubber with Self-Reinforcing Effect Based on Strain-Induced Crystallization

Natural rubber (NR) has a strategic position in the rubber industry due to its excellent properties, but it faces the problem of insufficient output and difficulty in recycling. Here, a high-performance elastomer was prepared by the simple epoxidation modification of bio-based Eucommia ulmoides gum (EUG). For the first time, it was found that epoxidized EUG (EEUG) with an epoxy degree of 12.3%–17.4% no longer crystallized at room temperature but had the ability to strain-induced crystallization (SIC). As a result, its vulcanizates showed excellent tensile strength (17 MPa), toughness (37.8 MJ m–3), and elasticity (strain recovery values >97%) without filler reinforcement, which is comparable with vulcanized NR. The SIC of EEUG was studied by synchrotron radiation wide-angle X-ray diffraction (SR-WAXD), and its performance was also compared with NR under the reinforcement of carbon black. In addition, through cross-linking by disulfide bonds, EEUG could be used to prepare high-performance (tensile strength of 10.5 MPa, toughness of 30.7 MJ m–3), recyclable green elastomers. This new kind of elastomer can be used as the second natural rubber, which is of great significance to solve the problem of insufficient production and difficult recovery of NR.