A Mild Interfacial Grafting Strategy for Enhancing Carbon Fiber‐Reinforced Polyamide 6 Composites

Surface grafting modification of carbon fiber (CF) faces the challenges due to complex reaction conditions and prolonged reaction time. It is urgent to develop mild and efficient methods for CF modification to meet industrial applications. Herein, we report a novel grafting CF modification technique at room temperature, where polyethyleneimine (PEI) is grafted to the activated CF, followed by amidation via interfacial polymerization. The modified CF is systematically characterized by surface chemical analysis and morphology evaluation. Mechanical testing reveals that the flexural strength and interlaminar shear strength (ILSS) of the modified CF reinforced polyamide 6 (CF‐PEI/PA6) composites reach 685.29 and 65.98 MPa, respectively, which are 68.42% and 62.01% higher than those of the desized CF composites. These enhancements are attributed to the synergistic effects of strong covalent bonding, rich active sites, and distributed cross‐linking regions brought by the continuous grafting layer at the interface. This method innovatively constructs the resin‐like structure on CF surface through fully covalent bonding, offering a mild and efficient pathway for interface modification of composite materials with potential for industrial‐scale application.