Sustainable natural rubber composites: masterbatch development of epoxidized natural rubber grafted to designed enzymatic polysaccharides

Abstract

Designed polysaccharides obtained from the enzymatic polymerization of sucrose, are employed as a sustainable, and functional reinforcing additive for rubber composites. The designed enzymatic polysaccharide used in this study is a semicrystalline, water-insoluble alpha 1,3-glucan. To facilitate the dispersion and bonding of an inherently polar filler in a nonpolar natural rubber matrix, this work employs an in situ melt process grafting of epoxidized natural rubber (ENR) onto the polysaccharide to achieve enhanced material properties. The temperature and shear-mediated melt grafting in the presence of two catalysts (i.e., sodium hydroxide (NaOH) and dicumyl peroxide (DCP)) were studied. Analytical characterization techniques, such as Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and solvent swelling was employed to validate the formation of covalent bonds between alpha1,3-glucan and ENR. Results indicate that the ENR–glucan composite using DCP provides improved properties. This formulation can be employed as a functional masterbatch for general NR composite formulations. The resulting NR–glucan–ENR formulation provided superior mechanical properties compared to incumbent reinforcing filler-based rubber formulations. These results suggest the potential utility of the polysaccharide for commercial deployment in products that benefit from improvements in mechanical and dynamic properties, in addition to overall composite weight reduction (e.g., transportation, shoe soles). Furthermore, the combination of a biosourced elastomer with a biobased reinforcing filler material technology provides an option to transition to a non-fossil composite system aligned with overall sustainability goals.