Solvent- and catalyst-free bio-conversion of waste polyurethane foams into high-performance 3D printing resin

The end-of-life treatment of thermoset polyurethane foam (PUF) is an environmental challenge that has remained unresolved for decades. Current chemical recycling strategies are economically prohibitive to implement due to the complex multi-step process and use of catalyst/solvent. Here, we report a one-step upcycling strategy that transforms PUF waste into 3D photo-printing resins without using any catalyst or solvent. Our process employs bio-based itaconic acid as a single reagent that not only degrades PUF into fragments but also generates photocurable vinyl end-groups in situ. Incorporation of additional bio-based monomers (tetrahydrofurfuryl methacrylate and l-lysine diisocyanate) allows formulation of a photo-sensitive resin. The corresponding 3D photo-printed polymer, made entirely from PUF waste and bio-monomers (excluding the photo-initiator), exhibits exceptional mechanical performance (tensile strength: 26.3 MPa, toughness: 16.2 MJ m^-3) relative to other commercial 3D photo-printed polymers. Our simple process that upcycles polymer wastes using solely bio-derived reagents points to a promising direction towards sustainable development of polymer materials.