Green Polyol Synthesis via Glycolysis and Aminolysis for Conversion of Waste Polyurethane and Polyethylene Terephthalate Into Flame‐Retardant Insulation Foam

ABSTRACT Polyurethane (PU) and polyethylene terephthalate (PET) have been extensively used for the production of plastic bottles, elastomers, and insulation foam. Through depolymerization processes, these plastic wastes can be converted into valuable monomeric and oligomeric compounds. In this study, bis(2‐hydroxyethyl) terephthalate (BHET), bis(2‐hydroxyethyl) terephthalamide (BHETA), and 4,4ˊ‐methylenedianiline (MDA) monomers and oligomers, as well as amide compounds, were obtained via glycolysis and aminolysis, serving as recycled polyols for synthesizing high‐value polyurethane foams (PUFs). The reaction products of depolymerization were directly utilized in the synthesis of repolymerized rigid PUFs without requiring any purification or separation processes, ensuring an economical approach. Deep eutectic solvents, composed of choline chloride and urea, along with zinc acetate catalysts, were employed for the depolymerization of waste PU and PET, achieving conversion rates of 98% for glycolysis and 100% for aminolysis. The resulting PUFs exhibited a total heat release of 18.4 kJ/g and a limiting oxygen index of 33.7%. This study highlights the successful production of high‐value functional materials from mixed green polyols derived from PET and PU depolymerization, offering an efficient and sustainable recycling method for potential mixed plastic wastes.