Recyclable High-performance Carbon Fiber Reinforced Epoxy Composites Based on Dithioacetal Covalent Adaptive Network

Abstract

Recycling of carbon fiber reinforced composites is important for sustainable development and the circular economy. Despite the use of dynamic chemistry, developing high-strength recyclable CFRPs remains a major challenge due to the mutual exclusivity between the dynamic and mechanical properties of materials. Here, we developed a high-strength recyclable epoxy resin (HREP) based on dynamic dithioacetal covalent adaptive network using diglycidyl ether bisphenol A (DGEBA), pentaerythritol tetra(3-mercapto-propionate) (PETMP), and vanillin epoxy resin (VEPR). At high temperatures, the exchange reaction of thermally activated dithioacetals accelerated the rearrangement of the network, giving it significant reprocessing ability. Moreover, HREP exhibited excellent solvent resistance due to the increased cross-linking density. Using this high-strength recyclable epoxy resin as the matrix and carbon fiber modified with hyperbranched ionic liquids (HBP-AMIM⁺PF₆⁻) as the reinforcing agent, high performance CFRPs were successfully prepared. The tensile strength, interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the optimized formulation (HREP20/CF-HBPPF₆) were 1016.1, 70.8 and 76.0 MPa, respectively. In addition, the CFRPs demonstrated excellent solvent and acid/alkali-resistance. The CFRPs could completely degrade within 24 h in DMSO at 140 °C, and the recycled CF still maintained the same tensile strength and ILSS as the original after multiple degradation cycles.