Antioxidative Behavior of an Eco-Friendly Chitosan-Based Biomass Macromolecular Antioxidant for Styrene–Butadiene Rubber (SBR)/Silica Composites

In this work, an eco-friendly chitosan-based biomass macromolecular antioxidant containing double bonds and polyphenol structure (COS-UC-GA), prepared by coupling 10-undecenoyl chloride (UC) and gallic acid (GA) onto chitosan (COS), was employed as an antioxidant for styrene–butadiene rubber (SBR)/silica composites. Its effects on the anti-aging properties of SBR/silica composites were systematically explored. The corresponding small molecular organic compound gallic acid (GA), commercial antioxidant butylated hydroxytoluene (BHT), and N-isopropyl-N′-pheny-p-phenyl-ene diamine (4010NA) were used as control samples. The results of the accelerated thermal-oxidative aging test, crosslinking density test, and thermogravimetric (TG) test demonstrated that the chitosan-based biomass macromolecular antioxidant COS-UC-GA can significantly enhance the anti-aging properties, thermal stability, and apparent activation energy (E) of SBR/silica composites. Moreover, the results of the extraction resistance test indicated that the chitosan-based biomass macromolecular antioxidant COS-UC-GA can present better migration resistance and extraction resistance in SBR/silica composites compared to the corresponding small molecular organic compound GA, commercial antioxidant BHT, and 4010NA. The superior antioxidative properties of the chitosan-based biomass macromolecular antioxidant COS-UC-GA for SBR/silica composites originated from the synergistic antioxidative effects between amine or amide groups of COS-UC-GA and polyphenol structure as well as the outstanding migration resistance and volatilization resistance of COS-UC-GA. The eco-friendly chitosan-based biomass macromolecular antioxidant COS-UC-GA can be used as a promising green candidate in the rubber industry to replace traditional small molecular antioxidants.