Development of reprocessable structural adhesives based on covalent adaptable networks for wind turbine blade

Abstract

Since the 2000s, the increasing installation of wind turbines has highlighted the challenges associated with the disposal of decommissioned turbines at the end of their service life. This study investigates solutions for enhancing the recyclability of composite materials generated during wind turbine decommissioning, while also addressing issues related to adhesive removal and disposal. This study addition of disulfide epoxy additive (DEA) into structural adhesives to introduce covalent adaptive networks (CANs). An optimal formulation was developed to ensure reprocessability while maintaining mechanical properties. The addition of DEA resulted in a decrease in mechanical strength and T_g, while reprocessability was enhanced. Reprocessing experiments showed that specimens with more than 15 wt% DEA recovered mechanical properties, with 20 wt% achieving the highest recovery (73 % of initial shear strength) after two cycles. Fracture surface analysis revealed a shift from brittle to ductile failure with increasing DEA. Fatigue testing also confirmed improved durability, with strength loss reduced from 57 % (0 wt%) to 26 % (20 wt%) after 1000 cycles. This phenomenon is attributed to the flexibility of the aliphatic structure, which reduces crack propagation rates while simultaneously promoting reversible bond dissociation and reformation. This study provides fundamental data for wind turbine blade waste management and recycling technology development. The findings are expected to contribute to the advancement of sustainable wind turbine materials.