The Surface Functional Coating Preparation On Carbon Fiber/Resin Composites

In order to improve the media corrosion resistance of carbon fiber/resin composites in special application conditions, the functional coating on carbon fiber/resin composites were prepared by the plasma surface technology. Because of the weak surface polarity and film bonding strength, plasma surface treatment of carbon fiber/resin composites was provided by Hall discharge plasma, then Al coating was deposited on the composites by DC magnetron sputtering. The effect of different plasma treating parameters and types on the surface wettability, microstructure, functional groups and mechanical property of the carbon fiber/resin composites, and the best plasma treating technological parameter were researched by contact angle measurement, tensile test, scanning electron microscope (SEM), metallographic microscopic analysis and infrared spectroscopic analysis (IR). The Al coating was characterized with X-ray diffraction (XRD) and scanning electron microscope (SEM). The influence of plasma treating powers on the film bonding strength measured by self-designed vertical pulling device, and the film bonding strength of Al coatings with different thickness before and after plasma treatment were evaluated. By the fluoride media corrosion resistance test, the property of fluoride media corrosion resistance of the carbon fiber/resin composites was learned before and after plasma treatment. The results are as follows:(1) After the plasma treatment, the contact angle of carbon fiber/resin composites decreases significantly while the surface wettability and free energy increases. The plasma treating result is closely related to technological parameters and plasma types. The contact angles decrease first and increase with plasma treating current and pressure, also reduce quickly and then tend to stability with the extension of plasma treating time. The best wettability of carbon fiber/resin composites is acquired when plasma treating current is1A, treating pressure is1Pa and treating time is10min respectively. For the same plasma treating technological parameter, the treating effect is improved for the three kinds of plasma in this study is O2>N2> Ar.(2) The plasma treating effect of carbon fiber/resin composites decrease gradually with the time going on, and it is related to the preservation surrounding and type of plasma. Although the treating effect will reduce over time, preservation in distilled water of room temperature can delay this reduction. The treating effect of O2plasma is superior to Ar plasma, and the effect of N2plasma is the worst.(3) The result of the metalloscope and SEM observation show that the surface granular impurities of carbon fiber/resin composites decrease, surface become rough and have obvious plasma etching trace after plasma treatment. The adhesion between carbon fiber and resin is enhanced. The result of the IR indicates that the quantities of C-C and C-O bonds on the surface of carbon fiber/resin composites treated by Ar plasma are decreased and increased respectively. Besides, carboxyl groups, ketone groups and alcoholic hydroxyl groups are increased, while ester groups are decreased. After N2and O2plasma treatment, the methyl and ester group of carbon fiber/resin composites are broken, accordingly CH2-O-CH2and C=N、C=N are formed respectively.(4) The film bonding strength of carbon fiber/resin composites are significantly enhanced after plasma treatment, and increases first and decreases with the rise of plasma treating current and reaches the best value when it is1.0A. The tendency of film bonding strength decreases with increasing the coating thickness moves downward, and the film bonding strength is2.88MP&, still large when the coating thickness reaches to25μm, but it is only1.22MPa before plasma treatment.(5) The fluoride media corrosion resistance test result shows that the average corrosion rate of carbon fiber/resin composites deposited with Al films in the fluoride media is4.17×10-3g/m2·h-1, and is perhaps an order of magnitude lesser than it without Al films, which is3.78×10-2g/m2·h-1. The fluoride media corrosion resistance of carbon fiber/resin composites is improved remarkably.