Study Of Ammonia Water Treatment On Carbon Fibers Under High Temperature And High Pressure

The carbon fibers (CF) have so many superior properties, such as high specific strength, high specific modulus, corrosion-resistant property and high temperature resistance, that are applied in composite as reinforcement. But the smooth surface and low content of active groups of CF restrict the interface properties of fiber and resin, so the modification is very essential.There is a coating of epoxy solution and some impurities on the surface of the CF utilized in this experiment. The CF was extracted with acetone and petroleum ester, and the effect of the treatment was evaluated. Then high temperature and high pressure ammonia water (HTHPAW) was used to treat CF. The acryl acid was used as monomers to graft on the treated CF. In order to determine the treatment mechanism, the surface pattern of CF was observed by scanning electronic microscope (SEM) and atom force microscope (AFM), and the surface element composites and functional groups were analyzed by X-ray photoelectron spectroscopy (XPS). The fracture pattern of the composites was observed by SEM. The interlamiar shear strength (ILSS) of the composites was tested by single-fiber pullout.The experimental results revealed that extracting with acetone and petroleum ether could remove the coating of epoxy solution and impurities on the surface of CF. After extracted by acetone and petroleum ester for both 24 hours, the tensile strength of the CF dropped from 3.45GPa to 3.37GPa., which indicated the influence of extraction to the intensity of CF was not obvious.The treatment of high temperature and high pressure ammonia water brought changes to the properties of the CF, such as surface structure, element composites and functional groups. The roughness degree of CF increased after the treatment, N and O content ratio and -C-N, -C=O, -COOH, -COOR functional groups amount increased, too. The results illuminated high temperature and high pressure ammonia water had mechanical erosion and oxidizing action, and the functions could modify CF surface property.The optimum craft was to adopt high temperature and high pressure ammonia water treatment on CF after extraction for 3 minutes at 350℃, and then the CF treated by HTHPAW was immersed in acrylic acid aqueous solution with concentrate of 3mass% at 70℃for 4 hours. The craft could improve the ILSS of composites from 61.17MPa to 86.21MPa, thus the ILSS increased 40.93%.