The Study Of Surface Treatments To Pan-Based Carbon Fibers

The properties of carbon fiber reinforced composites are always limited by the interfacial bond between fibers and matrix, Electrochemical treatment, carbon nanotubes depositing, Meldrum’s acid grafting were investigated to improve PAN-based carbon fiber surface activity, enhance carbon fiber/epoxy resin composite interfacial strength and preserve carbon fiber tensile strength in this study. X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), infrared spectroscopy (FTIR), atomic force microscope (AFM), Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were utilized to detect surface chemical composition, surface morphology and micro crystal structure of carbon fibers after treatments. Single fiber tensile strength and interlaminar shear strength (ILSS) of carbon fiber composite were tested to study carbon fiber mechanical property after treatments. Meantime, the changes of chemical and physical properties of different carbon fiber work flows in industrial were studied and the high temperature carbonized fibers were compared with the samples from Japan in compositions and structures.The surface functional groups changed after different oxidized time, the quantities of C-OH, C=O and COOH were increased during initial stage and then degraded to CO2 during late stage, the ILSS of carbon fiber/epoxy resin was sharply increased during initial stage and slightly increased during late stage. Carboxylic multi-walled carbon nanotubes (COOH-CNTs) mixed with sizing agent were uniformly deposited on carbon fiber surfaces, the wetting performance between fibers and epoxy resin was improved, ILSS of carbon fiber/epoxy resin was increased by 67% and fiber tensile strength was slightly increased by 6%. Meldrum’s acid was grafted with carbonyl group on carbon fiber surface to obtain carboxylic functionalized surface, the quantity of carboxylic groups was increased from 1.41% to 7.84%, there was no etching and coating on fiber surfaces, single fiber tensile strength was preserved and ILSS of carbon fiber/epoxy resin was enhanced by 74%.