Synergistic Optimization Tribological and Mechanical Properties of Carbon Fiber-Reinforced Recyclable Indole-Based Poly(hexahydrotriazine) Composites via FeOOH Nanoparticles and Fe3+–π Interaction

The sturdy and stable unique polyhedral structure of FeOOH nanoparticles facilitates stress and load transfer, thereby forming a tighter mechanical interlock at the carbon fiber–matrix interface. In this work, the FeOOH nanocrystal layer in situ grown on flexible carbon fiber cloth was rationally designed and fabricated through hydrothermal synthesis. Then, the non-covalent cation–π bond was constructed at the interface between the iron ion-loaded FeOOH nanoparticles and indole-based poly(hexahydrotriazine) (In-PHT). Owing to the collaborative effects of physical anchoring and chemical bonding, the resultant composite exhibited an outstanding tensile strength of 322 MPa, and the friction coefficient significantly decreased by 63% compared with the composites without FeOOH nanoparticles. Moreover, the resultant worn composite showed an excellent self-healing property owing to the introduction of polyethylene wax (PEW) with a low melting point, and the healed friction coefficient remained almost unchanged. Extensive analyses verify that the phase-separated structure and Fe3+–π interactions across multiscale interfaces achieve the combined advantages of wear resistance and durability for recyclable carbon fiber-reinforced poly(hexahydrotriazine) composites (PHT-CFRPs).