Polyphosphazene Nanotubes/carbon Fibers Hierarchical Hybrid Reinforcement for Improving Interfacial Adhesion of Polyamide 6 Composites

Continuous carbon fibers (CFs) reinforced thermoplastic composites have been gradually used as lightweight structural components for their excellent mechanical performances. However, the interface debonding and earlier damage of the composites tend to occur under external loading due to the inherently poor interfacial bonding between CFs and thermoplastic matrix. Herein, a layer of hierarchical poly(cyclotriphosphazene-co-4,4′-sulfonyldiphonel) (PZS) coating combining with nanotubes (PZSNTs) was assembled uniformly surrounding CFs surfaces to enhance the interface adhesion of the CF-reinforced polyamide 6 (CF/PA6) composites. Atomic force microscopy (AFM) and dynamic contact angle (DCA) measurement demonstrated that the PZSNTs coating significantly improved the surface roughness, wettability and surface energy of the modified CFs. An evident enhancement of interfacial shear strength (IFSS) was obtained from 37.68 to 52.32 MPa for CF-PZSNTs reinforced PA6 composites, showing an increase of 38.8