Novel synthesis of a soy-based polyol for a polyurethane rigid foam

A novel soy-based polyol was synthesised using a novel method. First, an allylic oxidation reaction was performed in a conventional flask. This step was followed by an epoxidation-hydroxylation reaction in a microflow system referring to the reported method, which was established by our team and could reduce the oligomerisation side reaction to improve the polyol quality. During the allylic oxidation process, hydroxyl groups were introduced to the oil main chain, which was confirmed by NMR, FTIR, and the determination of the hydroxyl number. The obtained soy-polyol labeled Polyol-a possessed a hydroxyl number of 378 mg KOH per g and a viscosity of 8825 mPa s. A corresponding soy-based polyurethane rigid foam labeled PU-a was also prepared. Compared with the previously obtained soy-based polyol without allylic oxidation treatment (i.e. Polyol-m), Polyol-a had a higher hydroxyl number. In addition, PU-a had a fine, uniform, and closed-cell morphology and exhibited excellent compression strength, thermal insulation, dimensional stability, and thermal stability. These properties were attributed to the high hydroxyl number of the soy-polyol, which created a high degree of crosslinking.