Fully Recyclable Aramid Fiber-Reinforced Composites with Superior Tearing Resistance Enabled by Reversibly Cross-Linked Poly(boron-urethane) Elastomer

Developing fully recyclable aramid fiber-reinforced composites (AFRCs) with satisfactory mechanical properties combined with excellent and facile recyclability remains a significant challenge. In this study, we report fully recyclable AFRCs with substantially improved mechanical properties by using a poly(boron-urethane) (PBU) elastomer as the matrix. The PBU elastomer network dissipates energy efficiently through the breakage and reformation of reversible hydrogen bonds. As a result, the designed composites (denoted as AFx-PBUy, where x:y denotes the mass ratio of AFs to PBU elastomer) achieve a high mechanical strength of ∼498 MPa and good tear resistance, with a fracture energy of ∼621.4 kJ m–2. Moreover, the reversible hydrogen bonds allow the AFx-PBUy composites to be fully recycled under mild conditions. Through this process, both the pristine AFs and the PBU elastomer can be recovered quantitatively without loss of performance. The recovered materials can be readily reassembled into regenerated AFx-PBUy composites, which display properties comparable to those of the original composites.