Synthesis and Characterization of Lignin-Based Polycarbonate Polyols for Flexible Polyurethane Foam Application

With the rising demand for sustainable materials, lignin-based polyols offer a promising renewable alternative to traditional petroleum-based polyols in flexible polyurethane (PU) foams. This study focuses on synthesizing novel high-performance lignin-based polycarbonate polyols via transesterification with dimethyl carbonate. The resulting lignin polyols exhibited hydroxyl values ranging from 111 to 179 mg KOH/g and viscosities of 12,000-26,000 mPa·s, thereby enhancing the suitability of lignin for flexible foam formulation. An in-depth structural analysis using proton, carbon, phosphorus, and 2D nuclear magnetic resonance confirmed the grafting of long polyether chains and the introduction of multiple carbonate linkages onto the lignin structure. Foams were formulated by replacing up to 60% of petroleum-based polyols with either synthesized lignin polyol or a mixture of lignin and soy polyols. Formulated foams demonstrated superior mechanical properties, including enhanced tensile strength and load-bearing capacity, compared to petroleum-based foams. Additionally, the developed foams with biobased polyols exhibited improved thermal stability, shock absorption, and partial biodegradability.