Polyurethanes (PU) were synthesized from lignin by first preparing a prepolymer from esterified sugar-based trihydroxyl compound xylaric acid and a 20 mol % excess of methylene diphenyl diisocyanate. The prepolymer was crosslinked with 5, 10, and 15 wt % of an industrial soda lignin, and polyethylene glycol was used to bring soft segments into the material structure. The total amount of bio-based starting materials was as high as 35%. Evidence for the reaction between the prepolymer and lignin was observed using Fourier transform infrared spectroscopic analysis and 13 C nuclear magnetic resonance spectroscopy. The thermal properties of the materials were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The mechanical and viscoelastic properties of the materials were determined by dynamic mechanical analysis (DMA).

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