Cosolvent‐Enhanced Dissolution of Long‐Chain Polyamides: Toward Room‐Temperature Material Recycling of Sustainable Composites

Polyamide 11 (PA11) is a fully bio‐based plastic featuring heat resistance and mechanical properties superior to polyolefins and carrying a relatively low carbon footprint (2–4 kg CO ₂ ‐eq). However, the high resistance of PAs to many common solvents such as alcohols and hydrocarbons makes them difficult to recycle by dissolution under mild conditions. In this work, a formic acid (FA)‐based cosolvent system exhibiting synergistic solvation through hydrogen bonds and dispersive interactions is shown to rapidly dissolve long‐chain PAs such as PA11 and PA12 at room temperature, which is not possible in pure FA due to its long alkyl segment. The regenerated PA11 shows no change in chemical structures or properties, and sufficient selectivity toward PA allows for facile separation and recovery of non‐PA materials from mixtures and composites, such as polypropylene (layered films) and carbon fiber cloth (woven laminates). This cosolvent strategy has the potential to change the thermoplastic recycling landscape by facilitating low‐energy recycling protocols of long‐chain PAs commonly found in bio‐based varieties.