Recycling of polyurethanes: where we are and where we are going

Polyurethanes (PUs) represent a family of useful synthetic polymers (thermoplastic or thermosetting) obtained from diisocyanates and diols/polyols via polycondensation reactions. Within the circular economy concept and also considering the current need for limiting the environmental impact of plastics, several methods have been designed, assessed, and exploited for the recovery at the end-of-life of polyurethanes and for their recycling. Indeed, the processing of polyurethane wastes can be significantly beneficial not only from an ecological but also from an economic point of view. At present, feedstock (namely, glycolysis) and mechanical recycling are the two most important strategies to recover and recycle polyurethanes; notwithstanding, “biological recycling”, an approach that exploits the biological degradation of the polymer, is gaining interest. This review aims to elucidate the recycling processes of both thermoplastic and thermosetting polyurethanes, providing the reader with some perspectives about their possible future developments.