Closed-Loop Recycling of Polyols from Thermoset Polyurethanes by tert-Amyl Alcohol-Mediated Depolymerization of Flexible Foams

The production of thermoset materials makes up 12% of global plastic production. With increasing demands for plastics and with emphasis on the legacy burden of thermoset polymers, new solutions are indispensable to shift our society from the current linear make–use–dispose mindset to a scenario where materials are utilized in a more circular fashion. In 2020, the production of polyurethane (PU) reached approx. 24 million tons, making it the sixth most produced polymer. However, the inherent stability of PU renders chemical recycling difficult, often providing a secondary feed with different characteristics and properties from the original polyol and isocyanate. In our previous work, we demonstrated how tert-amyl alcohol could be used as a solvent and reagent for the simple chemical recycling of PU via a solvolysis process. Herein, our efforts are presented for attaining a recycled polyol (recyclate) via chemical recycling of flexible thermoset PU foams using the tert-amyl alcohol-mediated solvolysis process and scaling it to produce new flexible thermoset PU foams. The produced recyclate is similar to virgin polyol, allowing for 100% substitution of virgin polyol for the recyclate while maintaining both mechanical and physical properties of the foams containing up to 64 wt % of recycled materials. Moreover, the foams prepared from the recyclate were also deconstructed to retrieve the recycled polyol, showcasing for the first time the possibility to form closed-loop polyol recycling processes for flexible PU foams. Finally, the recyclate was applied as a substitute for virgin polyols in the formulation of PU resins, where the recycled content amounted to 81 wt % while still attaining mechanical properties comparable to those of materials prepared with virgin polyol.