Effect of hybrid polysphosphazene coating treatment on carbon fibers on the interfacial properties ofCF/PA6composites

Carbon fiber (CF) reinforced polyamide 6 (PA6) composite has an extensive application. However, the performances of CF/PA6 composite are constrained by the poor interfacial adhesion between CF and PA6 matrix. In this article, in order to strengthen the interfacial adhesion of CF/PA6 composite, a layer of poly(cyclotriphosphazene-co-4,4 '-sulfonyldiphonel) (PZS) hybrid coating with plenty of PZS microspheres (PZSMS) was successfully introduced onto CF surface through facile in situ polymerization. After surface modification, the surface morphologies and the surface chemical structures of fibers changed distinctly. On one hand, the PZSMS provided more contact points and increased mechanical interlocking between CF and PA6 matrix. On the other hand, numerous hydrogen bonds between CF and PA6 were formed due to a great amount of unique polar groups on modified CF surface. Consequently, in comparison with untreated CF, the interfacial shear strength of CF-PZSMS/PA6 composites was improved from 37.68 +/- 3.16 to 53.79 +/- 3.38 MPa, by 42.75 +/- 3.02%. The results indicated that PZS hybrid coating on fiber surface effectively improved the interfacial adhesion of CF/PA6 composites, and the stronger hydrogen bonding and the enhanced mechanical interlocking synergistically played a major role in such significant improvements.