Hemicellulosic Sugars and Lignin: A Synergistic Combination for the Synthesis of High-Performance Bioresins

To render biorefineries economically viable, it is important to maximize the value of all of the processed lignocellulosic biomass. However, the hemicellulose fraction is often overlooked in current biorefinery strategies. In this study, we demonstrate the valorization of lignin and sugars, both obtained through dilute acid solvolysis of lignocellulosic biomass, for the production of lignin/sugar-based polyurethane (LSPU) films as partial substitutes for petroleum-derived polyols. LSPU films were prepared using a four-component system, comprising lignin, hemicellulose-derived sugars, polytetrahydrofuran, and hexamethylene diisocyanate isocyanurate trimer. Our study involved optimizing the sugar content in the LSPU film formulations to investigate how the presence of sugar impacts the films' structural, thermal, and mechanical properties. The results showed that as the concentration of sugar increased, the mechanical properties of the LSPU films were improved in comparison to those of sugar-free samples. Additionally, the LSPUs were evaluated as PU adhesives, where the mechanical properties of the bonded joints, comprising wood substrates, were measured using single-lap shear tests. The shear strength values obtained were comparable to or even higher than those of a commercial PU glue. Our findings demonstrate the potential of incorporating hemicellulose-derived sugars in LSPUs for improved mechanical and adhesion properties, offering new possibilities for the valorization of lignocellulosic derivatives.