Upcycling of Epoxy Resin in Wind Turbine Blades into High-Strength Adhesives

The recycling of waste wind turbine blades is the most important part of the green, low-carbon, and circular development of the wind power industry chain. The matrix polymers in wind turbine blades are mostly epoxy resin (EP) characterized by a stable crosslinked structure, which is insoluble, non-melting, and resistant to natural degradation. Although some advanced chemical recycling methods demonstrate the ability to structurally deconstruct EP into value-retained oligomers and show great potential for upcycling, problems such as harsh reaction conditions and low utilization and value addition of the degraded products (DEP) still exist. Herein, we present an innovative catalytic oxidation system in which EP is completely degraded using only 4 wt% catalyst at 100 °C for 6 h. Furthermore, this methodology enables the selective cleavage of C‒O bonds in EP, yielding hydroxy-rich DEP. DEP can be completely and directly used as adhesives with an adhesive strength of 10.34 MPa, which exceeds that of commercially available adhesives and some adhesives prepared by copolymerization of fresh raw materials. Moreover, this adhesive is also resistant to acids and alkalis and is easy to remove. In addition, the reaction reagents, catalysts, and reinforcing fibers in the composites within the degradation system can all be recovered. In particular, the recovered catalysts can be recycled up to 5 times. This gentle, efficient, and green system not only has important reference significance for the sustainable development of the wind power industry but also provides new ideas for the design of high-strength adhesives.