Synthesis of rigid polyurethane foam from bio-based polyol obtained from microwave-assisted depolymerization of corn cob waste

This study presents an innovative upcycling methodology for the production of rigid polyurethane (PUR) foams using a biopolyol (BioPol) synthesized from corn cob lignocellulose waste. The BioPol was obtained through microwave-assisted (MW) irradiation under acidic catalysis, followed by neutralization of the acidic medium. Rheological characterization of the lignocellulose-derived BioPol was conducted to evaluate its suitability for industrial applications. The PUR foam formulation was designed based on the hydroxyl number of the BioPol, as determined by ASTM D4274. BioPol was combined with a commercial trifunctional polyol derived from the oxypropylation of glycerol, enabling the entire polyol component of the formulation to be classified as bio-based. Increasing the BioPol content in the formulation enhanced the cross-linking density of the resulting foams, which also led to a reduction in the average pore diameter. Uniaxial compressive strength tests revealed superior mechanical properties, with maximum resistance recorded at 3.18 MPa compared with the blank sample. The resultant high-density rigid PUR foams exhibit excellent thermal stability, mechanical robustness, and ease of processability, establishing a promising pathway for developing durable and eco-friendly bio-based polyurethane products.