Kraft Lignin-Based Rigid Polyurethane Foam

Abstract

Kraft pine lignin was derivatized to a liquid polyol through oxypropylation. The resulting polyol was characterized by GPC, FT-IR, H1, C13, and P31 NMR and was compared to commercial polyols in view of the mechanical property of the corresponding rigid polyurethane foams for the first time. A series of lignin-based PU was synthesized by replacing varying weight percentages of the amount of sucrose polyol and glycerol polyol, two commonly used commercial polyols employed in the control foam preparation. All foams had a low density of ∼30 Kg m−3 and showed typical linkages of PU in the FT-IR spectra. The diameter of closed-cells was ∼650 μm for most of the foams as revealed by SEM images. The optimal compressive property of rigid PU foams was obtained using lignin polyol without the addition of any other commercial polyols primarily attributed to the rigidity of lignin aromatic structure and the high functionality of lignin hydroxyl groups.