Study On Microwave-induced Oxidation Of Carbon Fibers Surface

Carbon fibers have a lot of advantages, and the application of carbon fibers and composite materials in the aerospace, transportation, military and sports equipment reflects the great superiority. The interface between carbon fibers and matrix plays a critical role in controlling the overall properties of the composites. However, due to the inert surface of the carbon fibers, there are little reactive functional groups, which greatly affect the composite compose of the carbon fibers and the matrix. So surface treatment of carbon fiber is necessary.A new method of surface treatment for carbon fibers, i.e. oxidization with hydrogen peroxide under microwave radiation, was developed by our group. The surface of different types of carbon fibers, such as PAN based and mesophase pitch based carbon fibers (MPCF), and the same kinds of carbon fibers made by different carbonation temperature, which is T1(MP1), T2(MP2) and T3(MP3), were treated by the way above. The physical and chemical properties on fiber surfaces were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-Vis spectroscopy. Besides, The interface property of carbon fibers and epoxy resin was studied by thermal mechanical analysis (TMA), so that to evaluate the modification effect on the carbon fibers.The oxygen on the surface of carbon fibers was increased by the results of XPS, while the extent of increase was different. Compared with different kinds of carbon fibers, the oxygen of MPCF is greater than the increase of amplitude of PAN based carbon fibers; Compared with different carbonation temperatures of carbon fibers, MP2 carbon fibers increase the sharpest. It is the carbonation temperature and kind of carbon fibers influence the modification effect. Comparing the surface morphology of the carbon fibers after different oxidized treated time and ultrasonic, it found grooves of PAN and MPCF were etched with graphite flake desquamating to result in the surface became smooth and roughness decreased. However, the etched of smooth isotropic pitch based carbon fibers was very homogenous and the roughness of surface increased after treatment due to the its intrinsic property. But the smooth surface of isotropic pitch based carbon fibers, due to the nature of the fiber itself makes the surface more uniform etching, and after treatment the surface becomes rough. In addition, the graphite sheet flaked off from the surface of graphite and carbon fibers by ultrasonic became thinner and the content increase with the increase of oxidation treatment time.Dynamic mechanical properties of carbon fiber/epoxy resin composite material (CFRP) was studied by TMA. The glass transition temperature (Tg) of treated carbon fibers/epoxy resin composite increased by 5.6 ? than untreated, and the loss tangent reduced by 11.3%. The interface property of carbon fibers/epoxy resin composites was improved. The treated carbon fibers/epoxy resin composite average thermal expansion coefficient (at30-100?) is 2/5 and 1/10 of untreated and pure epoxy resin, respectively.