Chemolysis of Bio-Based Polyurethane Foams with Different Biopolyol Contents: Recovery and Possibility of Rebiopolyols Reuse in Sustainable Polyurethane Systems

Rigid polyurethane foams obtained using different amounts of biopolyol synthesized via transesterification of rapeseed oil with triethanolamine were subjected to glycolysis in order to obtain rebiopolyols. It was demonstrated that the biopolyol content in the parent foam influences both the chemical structure and the properties of the recovered rebiopolyols. FTIR and GPC analyses confirmed changes in the proportions of urethane, ester, and ether linkages. They also revealed the release of free triethanolamine and the formation of monoglycerides resulting from partial cleavage of fatty acid ester groups originally present in the biopolyol. Increasing the biopolyol content led to a reduction in the viscosity and the number-average molecular weight, along with an increase in the amine number. The rebiopolyols were preliminarily evaluated in polyurethane formulations, and FOAMAT measurements indicated an increase in the foaming reactivity with a higher amine content. Complete replacement of the petrochemical polyol with rebiopolyols was possible only when the starting foam contained up to 50 wt% biopolyol, while higher biopolyol contents resulted in excessive reactivity. These results demonstrate that the biopolyol content in the foam subjected to glycolysis is the key factor determining the suitability of rebiopolyols for reuse in the synthesis of new polyurethane foams.