Synthesis and Characterization of Innovative Polyurethane Foams from Cellulose and Citric Acid-Derived Bio-Based Polyols

Abstract The limited availability of fossil resources and the environmental problems they cause have made the development of bio-based raw materials for producing polyurethane (PU) foam a priority. In the literature, glycidol and ethylene carbonate are commonly used for cellulose liquefaction. However, glycidol has the disadvantages of toxicity and high cost, while ethylene carbonate has the disadvantage of high cost. In this study, an environmentally friendly, safe, and economical bio-based polyol synthesis method based on the esterification of citric acid and glycerin was developed as an alternative. The resulting bio-based polyol was used in place of conventional polyol at 25%, 50%, and 75% replacement levels to produce rigid PU foam. The microstructure, crosslink density, water absorption capacity, flexural strength (three-point bending test), thermal stability, and flame-retardancy performance (UL-94 V) of the foams were evaluated. The results showed that as the amount of bio-based polyol increased, the maximum decomposition temperature increased to 423 °C. The water absorption capacity, which was 748.1% for the standard PU foam, decreased to 197.2% and 196.1% in the formulations containing 50% and 75% bio-based polyol, respectively. The formulation containing 50% bio-based polyol demonstrated the best performance in terms of mechanical, physical, and thermal properties, with a 166.6% increase in flexural strength compared to that of the standard PU foam. In addition, the 50 and 75% bio-based formulations met the UL-94 V1 and V0 flame-retardancy ratings, respectively. The findings indicate that cellulose-based biopolyols synthesized through the esterification of citric acid/glycerin/cellulose represent a promising alternative for developing sustainable, high-performance PU foams.