Study On Anodic Oxidation Surface Treatment Of PAN-Based High-Modulus Carbon Fibers By Cyclic Voltammetry

Anodic oxidation is widely used in carbon fiber surface modification for its advantages of controllable, stable effect and so on. Homemade PAN-based high-modulus carbon fibers (HMCF) were electrochemically oxidized by cyclic voltammetry multi-scans in several different electrolytes. The nature of electrolyte and theory of anodic oxidation was studied by analyzing the differences between scanning curves, and then carbon fibers were treated with the method of continuous constant-current anodic oxidation. Performance of carbon fiber surface and CFRP were investigated, the chemical titration method and SEM were used to study the changes of functional groups and morphology of carbon fibers surface; the adhesive properties of carbon fibers/epoxy resin were characterized in terms of interlaminar shear strength (ILSS), and the conclusions were as follows:â‘ PAN-based high-modulus carbon fibers were electrochemically oxidized by cyclic voltammetry multi-scans in several different electrolytes, The results show that there is much difference of CV curves in each electrolyte solutions. In the solution of H2SO4, there are three oxidation peaks in the CV curve, three kinds of functional groups such as carboxyl,hydroxyl and ester on the fiber surface treated in H2SO4 are much more than untreated. In the solution of NH4H2PO4, there is one oxidation peak in the CV curve, and oxidation peak current is growing with the process of scanning, three kinds of functional groups such as carboxyl,hydroxyl and ester on the fiber surface treated in NH4H2PO4 are more than untreated but less than treated in H2SO4. The back-ground current in KOH is higher than those in other electrolytes, and the roughness of fibers surface have been changed most after treated. These results show that oxidation peak on CV curves can be used to express the nature of different electrolytes and the performance of carbon fiber oxidation process, while the background current can be used to indicate physical etching to the fiber surface. This conclusion shows that cyclic voltammetry can be used to study nature of electrolyte and filtrate proper electrolyte for treating carbon fiber.â‘¡In the same scanning conditions, if scan range was limited to-0.3 0.6V, there will no oxidation peaks appear in CV curves in solution of NH4HCO3, NH4H2PO4. It proves that oxidation progress will not occur on the fiber surface if there isn't active oxygen reaction in the system. This result correspond the present mechanism of anodic oxidation. It considered that high activity oxygen which separate out from water in the progress electrochemical oxidation attached to fiber surface to promote chemical reaction to produce oxygen-containing functional groups. These results also proved cyclic voltammetry curves have close relationship with oxidation process, and it is feasible that cyclic voltammetry be used to study mechanism of anodic oxidation.