Formation of Ligno-Polyols: Fact or Fiction

The physical and chemical characteristics of several lignin-polyol blends were investigated by qualitative and quantitative methods from the view of biobased polyurethane applications. Four differently isolated biomass lignins from forestry and agricultural residues were blended with polyester polyol, and one was blended with polyethylene glycol. The isolated products were examined thoroughly to elucidate the subsequent lignin and polyol interactions during the premixing stage of biobased polyurethane formulation. Polyol was detected in lignin even after vigorous washings with several organic solvents and Soxhlet extraction. The experimental data coupled with two-dimensional heteronuclear multiple quantum coherence (HMQC) and nuclear magnetic resonance (NMR) spectroscopy confirmed the formation of ligno-polyols via strong intermolecular attractions, as well as some linkages between several lignin hydroxyl and polyol functional groups.