Fabrication of Bio-Based Flexible Polyurethane Foam with Biodegradation by Etherification of Kraft Lignin

Polyurethane foam (PUF) is highly valued in various industrial applications due to its excellent specific strength and thermal insulation properties. As we pivot toward sustainable development, bio-based PUF has emerged as a promising alternative. Central to this transformation is the synthesis of biopolyols, which facilitate the preparation of biodegradable PUF. In this study, we successfully synthesized lignin-based polyols (LP) by introducing hydroxyl groups into Kraft lignin. The resulting LP remained in liquid form at room temperature and exhibited high reactivity, as evidenced by a hydroxyl content of 6.38 mmol/g. We further developed lignin-based polyurethane foam (LPUF) by substituting conventional petroleum-based polyols with LP, in proportions ranging from 20 to 100%. The presence of a rigid benzene ring in LP imparted enhanced mechanical and thermal properties to the LPUF. Remarkably, the stress at 70% strain of LPUF reached 86.80 kPa when 60% of LP was used as a substitute, approximately nearly four times better than that of conventional petroleum-based PUF. Additionally, biodegradation experiments revealed that LPUF with 100% LP substitution degraded by 17.36% over 180 days, a rate significantly higher than the 4.36% observed in petroleum-based PUF.