Enhanced interfacial strength of carbon fiber/PEEK composites using a facile approach via PEI&ZIF-67 synergistic modification

As a kind of metal-organic frameworks (MOFs) which possess large specific surface area and excellent thermal stability, zeolitic imidazolate framework-67 (ZIF-67) shows great application potentials because it can be synthesized in aqueous solutions at room temperature. In this work, we propose a synergistic strategy by taking advantages of polyetherimide (PEI) and ZIF-67 to enhance the interfacial strength of carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites via a facile route. The bare CF is simply immersed into PEI solution and the aqueous solution of ZIF-67 precursors stepwise at room temperature to wrap PEI intermediate sizing layer and in situ grow ZIF-67 crystals. The surface morphology of CF indicates that regulating the concentration of PEI sizing agents can control the relative amount of ZIF-67 adhered onto CF surface. After modification, the tensile strength of single CF shows no deterioration and the interfacial shear strength (IFSS) of as-prepared modified CF/PEEK reveals an increase of 40.5%. Besides, the enhanced interfacial interaction mechanism might be ascribed to miscible feature of PEI with PEEK and rough structure from ZIF-67. This work may shed some light on establishing a facile and effective synthetic approach to modify CF and improve the performance of composites without degrading the mechanical property of pristine CF.