Solvent-, Catalyst-, and Heating-Free Mechanochemical Depolymerization of Polyurethane

Polyurethane (PU) is one of the most versatile synthetic polymers; however, its cross-linked structure and inherent durability present significant challenges for recycling. Conventional depolymerization methods, such as glycolysis, aminolysis, and hydrolysis, typically require high temperatures, prolonged reaction times, or additional catalysts, thereby limiting their sustainability and scalability. In this study, we report a solvent-, catalyst-, and heating-free mechanochemical method for the depolymerization of commercial PU under ambient conditions using only sodium hydroxide. Reaction parameters were optimized using a model urethane compound to enable efficient urethane bond cleavage, with reaction progress monitored by NMR and HPLC. The method was subsequently applied to commercial PU products, including kitchen sponges and household insulation foam. Up to 69% polyol recovery was achieved within 3 h of ball milling without external heating. This mechanochemical approach markedly reduces solvent usage while simplifying the depolymerization process, offering a practical route for polyol recovery from PU waste. These findings highlight the potential of solid-state mechanochemistry as a viable platform for sustainable polymer valorization.