Exploring the unique UV-thermo-oxidative resistance characteristics of natural rubber induced by non-rubber components

Diene rubbers are prone to aging due to their unsaturated structure, a key factor limiting their industrial applications. Nevertheless, although natural rubber (NR) and synthetic cis-polyisoprene (PI) are both diene rubbers with similar molecular chain structures, NR exhibits markedly superior aging resistance compared to PI. In our recent studies, we found that removing non-rubber components (NRCs) results in a 4.68-fold (from 58.10 % to 12.42 %) decrease in the retention of mechanical properties in NR samples after 96 h of UV-thermo-oxidative aging, confirming that NRCs contribute to NR's excellent aging resistance. To elucidate the underlying mechanism from the molecular level, we analyzed the evolution of the crosslinking network in NR with different NRCs content using FTIR and XPS, and monitored free radical dynamics through EPR. The results demonstrate that NRCs improve aging resistance by modifying crosslinking bond types, inhibiting network degradation, and scavenging free radicals to suppress chain scission reactions. Interestingly, by incorporating acetone extract (AE) and its key antioxidant component α-tocopherol into PI, the superior UV-thermo-oxidative resistance of NR is effectively replicated in synthetic rubber. By incorporating AE, the mechanical properties retention of PI improved by 2.30-fold after 72 h of aging. Furthermore, the addition of 1.0phr α-tocopherol enhances the tensile strength retention of PI from 45.77 % (9.37 MPa) to 69.89 % (14.30 MPa) after 48 h of aging, indicating its significant contribution to improving UV-thermo-oxidative resistance. This work not only provides innovative strategies for designing biomimetic rubbers but also proposes a green and sustainable strategy for enhancing the durability of diene rubbers.