Preparation of a precursor complex containing lignin/silica hybrids and styrene-butadiene rubber via a one-pot method to fabricate high-performance rubber materials

Lignin/silica hybrids are promising rubber-reinforcing fillers because of their low cost and renewability. Phosphorylated kraft lignin (PKL), Na₂SiO₃·9H₂O, and styrene-butadiene rubber (SBR) were used in this study to prepare a PKL-SiO₂/SBR complex via a simple one-pot method. The PKL-SiO₂/SBR complex was subsequently processed to produce rubber composite materials. PKL was successfully synthesized, as shown by the results of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). The as-prepared lignin/silica hybrid "PKL-SiO₂" formed microspheres with an average particle size of 447.5 nm, a mass ratio (PKL:SiO₂) of 43.6 %, and weak hydrophilicity. Compared with carbon black-filled rubber, the PKL-SiO₂/SBR composites had better mechanical properties but lower rolling resistance and dynamic heat generation. These characteristics were attributed to the fact that the small PKL-SiO₂ fillers were uniformly dispersed in the rubber matrix and exhibited strong interfacial affinity for the rubber matrix. Moreover, PKL-SiO₂ contributed to the formation of an insulating layer on the rubber surface, thereby reducing the total heat release and total smoke production. This study provides scalable and cost-effective ways to fabricate rubber composite materials that are reinforced by renewable biobased functional fillers.