Sustainable Waterborne Polyurethane Adhesive With Superstrong Adhesion Performance and Excellent Weatherability from Biomass Lignin and CO 2 ‐Based Polyols

Abstract Utilizing biomass and CO 2 to synthesize biodegradable and reusable polymeric materials is critical for addressing the dual challenges of petrochemical resource depletion and environmental pollution. Among emerging alternatives, CO 2 ‐based polyols (PPC) exhibit exceptional promise in replacing petroleum‐based polyols; while, lignin stands as the most abundant aromatic biomass resource. However, integrating these feedstocks to produce high‐performance polymeric materials with combined biodegradability, recyclability, and reusability remains technically demanding. In this work, a lignin‐based waterborne polyurethane adhesive (LWPU) is developed using PPC and low‐molecular‐weight lignin (AOH), achieving a high solid content (53.2%) and outstanding overall properties. The incorporation of lignin strengthens hydrogen‐bonding networks and increases crosslinking density, thereby enhancing cohesive energy density. The optimized LWPU demonstrates robust adhesion on diverse substrates, with lap shear strengths reaching 14.7 MPa (wood), 10.6 MPa (steel), and 9.0 MPa (aluminum). Notably, it maintains structural integrity under extreme thermal variations (–30 °C to 100 °C), high‐humidity (95% ± 5% RH), and prolonged ultraviolet (UV) irradiation conditions. Further, the lignin‐reinforced dynamic covalent and hydrogen bonds impart exceptional recyclability and reusability to the adhesives. This methodology establishes a sustainable pathway for designing high‐performance bio‐adhesives that synergistically utilize biomass and CO₂‐derived feedstocks.