Engineering of Reversibly Cross‐Linked Elastomers Toward Flexible and Recyclable Elastomer/Carbon Fiber Composites with Extraordinary Tearing Resistance

Abstract Carbon fiber (CF)‐reinforced polymers (CFRPs) demonstrate potential for use in personal protective equipment. However, existing CFRPs are typically rigid, nonrecyclable, and lack of tearing resistance. In this study, flexible, recyclable, and tearing resistant polyurethane (PU)‐CF composites are fabricated through complexation of reversibly cross‐linked PU elastomer binders with CF fabrics. The PU‐CF composites possess a high strength of 767 MPa and a record‐high fracture energy of 2012 kJ m −2 . The high performance of the PU‐CF composites originates from the well‐engineered PU elastomer binders that are obtained by cross‐linking polytetrahydrofuran chains with in situ‐formed nanodomains composed of hierarchical supramolecular interactions of hydrogen and coordination bonds. When subjected to tearing, the force concentrated on the damaged regions of the PU‐CF composites can be effectively distributed to a wider area through the PU binders, leading to a significantly enhanced tearing resistance of the composites. The strong interfacial adhesion between PU binders and the CF fabrics enables the fracture of the CF in bundles, thereby significantly enhancing the strength and fracture energy of the composites. Because of the dynamic nature of the PU elastomer binders, the PU‐CF composites can be recycled through the dissociation of the PU elastomer binders.