Dual-functionalization of lignin towards superior reinforcement for styrene-butadiene rubber

Developing lignin-based fillers for reinforcing rubber materials has been recently spotlighted. This work modified lignin via a simple amination and a silylation reaction in a one-pot two-step manner. The molecular structure of aminated lignin (LN) was verified using 2D-HSQC, XPS and elemental analysis. The following silylation on LN results in dual-functionalized lignin (LNSi). LN and LNSi show improved hydrophobicity, reduced Hansen solubility parameters and morphology of nanoparticles (<50 nm). Styrene-butadiene rubber (SBR) composites containing 40 phr of fillers were prepared through latex compounding. SBR-LNSi presents comparable tensile strength to the references with carbon black and silica, and enhanced hardness. These remarkable mechanical performances correlate with its high dispersity and affinity with SBR matrix, and the improved rigidity and structuredness due to the self-condensation of silanol groups. This study provides a proof-of-concept for designing lignin-derived fillers with superior reinforcing effect on rubber materials.