High bio-content polyurethane composites with urethane modified lignin as filler

Abstract In order to improve the compatibility between lignin fillers and polyurethane matrix, two different chemical strategies were used to modify the lignin macromolecules. Modified lignin was incorporated into vegetable oil-based polyurethanes to produce composites with high bio-content. Lignin modified with octadecyl isocyanante (lignin urethane) was found to be more compatible with the polyurethane matrix than lignin modified with butyric anhydride. The effect of lignin urethane loading on the thermo-mechanical properties, thermal resistance, and dielectric properties were investigated. High lignin content (up to 30 wt. %) increased the Young's modulus and lowered the onset of thermal degradation. Incorporation of lignin urethane did not change the glass transition temperature of the polyurethane composites significantly, but it increased the dielectric constant compared to neat polyurethane. This work provides an effective way of using lignin as a low-cost bio-renewable resource in the polyurethane industry.