Electrode Potential Regulation of Carbon Fiber Based on Galvanic Coupling and Its Application in Electrochemical Grafting.

The reaction behavior of carbon fiber in electrochemical grafting is related to its electrode potential. In this paper, carbon fiber and metals with different electrode potentials were used to form combined electrodes to regulate the electrode potential of carbon fiber. The results showed that galvanic coupling was formed in the combined anode when the potential difference between carbon fiber and the metal (Δϕ = ϕCF0 - ϕmetal) was higher than 0.05 V. The electrode potential of carbon fiber was reduced due to cathodic polarization. The electrode potential of carbon fiber after galvanic coupling was proportional to the self-corrosion potential of metals. By applying the electrode potential regulation of carbon fiber in the electrochemical grafting of poly(glycidyl methacrylate) onto the carbon fiber surface, the grafting effect was significantly improved with the decrease of the electrode potential of carbon fibers. The grafting amount of carbon fibers increased from 0.83 to 69.86% as the electrode potential of carbon fibers dropped from 0.55 to -0.72 V. Consequently, the interfacial shear strength of the carbon fiber composite was remarkably promoted from 47.59 to 81.41 MPa, increasing by 71.07%.

Electrochemical grafting of poly(glycidyl methacrylate) on a carbon-fibre surface.

In this work, glycidyl methacrylate (GMA) was polymerised and grafted onto the surface of carbon fiber (CF) by using electrochemical grafting to improve the interfacial properties between the fibre and epoxy resin. The optimised conditions for electrochemical grafting and the reaction mechanism were also investigated. Results showed that GMA was covalently grafted to the CF surface by the assistance of aluminium chloride, which is a good electrolyte for electrochemical grafting. The GMA grafting ratio on the CF surface increased with electrolyte concentration and reaction time, and an optimal current intensity for the electropolymerisation was determined. On the basis of the strong correlation between the grafting ratio and the carboxyl content in the CF, a two-step mechanism of electrochemical grafting on the CF surface was proposed: first, the surface of CF was anodised to produce oxygen-containing functional groups, mainly including COOH, OH and C[double bond, length as m-dash]O. Next, when CF was used as the anode in the electrical grafting reaction, the COOH on the surface of CF would lose electrons and then remove carbon dioxide to generate carbon radicals on the surface of CF. The carbon radical would attack the carbon-carbon double bond in GMA to initiate the radical polymerisation of GMA monomers and graft polymers would be formed on the CF surface. Compared with untreated CF, the interfacial shear strength (IFSS) test proved the improvement of the interface adhesion of the modified carbon fibre (mCF) composites. This work provided a controllable electrochemical approach that could simply and quickly graft poly(glycidyl methacrylate) (PGMA) on the surface of CF.