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Graphene oxide (GO) was grafted onto the surface of carbon fiber (CF) by two synthetic routes with hexamethylene diisocyanate (HDI) tripolymer as the coupling agent. The first one was to use HDI tripolymer to modify the surface of GO, named GO-NCO, and then graft GO-NCO onto the oxidized carbon fiber surface. The other route was to use HDI tripolymer to modify the oxidized carbon fiber surface, named CFO-NCO, and then graft GO onto the CFO-NCO surface. The chemical compositions of the CF surface were confirmed by infrared spectroscopy (FTIR) and X-ray photoelectron spectra (XPS). The surface morphologies of CF after modification and debonding from matrix were examined by scanning electron microscopy (SEM). The interfacial shear strength (IFSS) of CF/PA6 composites was also investigated by microbond test. It is found that the interfacial properties of GO modified carbon fiber reinforced polyamide 6 (CF-g-GO/PA6) composites are better by using the first route. The IFSS of CF-g-GO/PA6 composites reaches 61.4 MPa, is an increase of 40.2% compared with that of unmodified CF/PA6 composites. Moreover, the interfacial enhancement mechanism was further analyzed in detail.

Introducing nanoscale reinforcements into the interface between carbon fiber (CF) and resin is an effective approach to improve the interfacial adhesion of CF composites. In this paper, a facile one-pot polymerization process provides a rapid and efficient method for preparing polyphosphazene microspheres/CF hybrid reinforcement using hexachlorocyclotriphosphazene (HCCP) and bis(4-hydroxyphenyl) sulfone (BPS) as monomers. By the in situ polymerization modification, HCCP and BPS were successfully cross-linked and deposited on the CF surface. Scanning electron microscope and atomic force microscopy images show that poly(cyclotriphosphazene- co -4,4′-sulfonyldiphonel) microspheres were introduced onto the CF surfaces and the surface roughness of fibers is enhanced obviously. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm that the polymerization between HCCP and BPS has been successfully carried out. The surface modification can significantly increase the fiber roughness, polarity, wettability and surface energy, thus improving the interfacial shear strength of CF/epoxy composites. Meanwhile, the single fiber tensile strength of CF also shows an increase after modification.

To improve the interfacial properties of carbon fiber (CF) reinforced composites, an innovative and simple functionalized strategy has been proposed by grafting 4,4'-oxydianiline (ODA) onto carbon fiber surface using hexachlorocyclophosphazene (HCCP) as a novel coupling agent at mild reaction conditions. The chemical composition of the CF surface was confirmed by X-ray photoelectron spectra (XPS). The surface topography and surface energy of CF were examined by atomic force microscope (AFM) and dynamic contact angle tests (DCA), respectively. The interfacial shear strength (IFSS) of CF reinforced composites was studied by microbond test. The tensile strength of CF was measured by single filament tensile test. After functionalization treatment, the grafted amine groups on the fiber surface enhanced the surface wettability of modified CF and formed strong chemical bonding between fiber and matrix, improving the interfacial adhesion strength of composites. The interfacial shear strength of modified CF reinforced composites increased by 71.2% compared with that of desized CF. The interfacial enhancement mechanism was also discussed in detail. Moreover, the modified CF almost kept the original mechanical properties after functionalization. (C) 2014 Elsevier B.V. All rights reserved.