Dual-feedstock bio-based polyurethane elastomers from lignin polyol and PHB-diol with enhanced mechanical and thermal...

Growing concerns over plastic waste and fossil-based polymers highlight the need for sustainable elastomers. Conventional polyurethane elastomers exhibit limited degradability, while bio-based alternatives using lignin or poly(3-hydroxybutyrate) (PHB) alone often compromise mechanical performance or processability. This study introduces a dual-feedstock strategy incorporating liquefied organosolv lignin polyol and PHB-diol as co-reactive polyols within a poly(ethylene glycol)-isophorone diisocyanate (PEG-IPDI) network. Elastomer films with varying PEG/IPDI ratios were synthesized and characterized by FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, atomic force microscopy, and tensile testing. FTIR carbonyl deconvolution confirms covalent incorporation of both biopolyols and quantifies a high degree of urethane hydrogen bonding (DU% = 83.1-85.6%) in the dual-feedstock LPPU series, consistent with a well-developed hard-segment domain structure. The optimized LPPU2 formulation (PEG600:IPDI = 1:4, 1 g each lignin polyol and PHB-diol) exhibits markedly improved thermal stability, with a 5% weight-loss temperature of 260.2 °C and 2.80 wt% char residue at 600 °C, compared with 158.9 °C and 1.75 wt% for neat PU. Tensile measurements show that LPPU2 achieves an ultimate tensile strength of 40.1 ± 5.6 MPa at 281 ± 24% elongation at break - a nearly four-fold strength increase over neat PU while maintaining elastomeric extensibility. AFM phase imaging confirms that PHB-diol co-incorporation yields the most uniform domain morphology (Ra = 2.38°) among all formulations, correlating with LPPU2's superior toughness. Overall, this study demonstrates that rational co-incorporation of chemically distinct bio-based polyols enables dual-crosslinked polyurethane networks that synergistically balance stiffness, elasticity, and thermal stability.