Carbamate‐Containing Decrosslinkers for Reactive Melt Extrusion Deconstruction of Crosslinked Polyurethane Composites

The covalently crosslinked nature of polyurethane (XPU) composites prohibits common melt reprocessing methodologies, further complicated by the fillers added. State‐of‐the‐art solvolytic depolymerization methods, including glycolysis, typically require high temperatures/pressures/energy‐intensive separation techniques and largely fail to recover viable PU precursors at high purity. Reactive melt extrusion deconstruction (RMED) emerges as a novel approach to transform XPU thermosets into reprocessable thermoplastics. This process leverages catalyzed dynamic carbamate exchange in a twin‐screw extruder, where low‐molecular‐weight carbamate decrosslinkers (DX) simultaneously decrosslink XPU and functionalize the deconstructed PU in the melt state. Our previous work used a library of low‐molecular‐weight carbamates to decrosslink neat XPU. This study expands the RMED materials pallet to include XPU composites synthesized with Al 2 O 3 fillers and investigates how Al 2 O 3 inclusion affects RMED kinetics and structure‐property‐processing relationships. Primarily, RMED offers an efficient, rapid process to deconstruct difficult‐to‐dispose XPU composites into melt‐processable slurries with high filler content. Furthermore, the RMED kinetics remain rapid in the presence of both fillers and emerging non‐toxic catalysts. Adjusting DX concentration and structure modulates gel content and molecular weight (thus viscosity) of deconstructed PUs. Overall, this manuscript reports a robust RMED platform for XPU composite upcycling, potentially applicable to many other thermosets/composites with dynamic exchange capabilities.