Study On Oiling Agents Of Mesophase Pitch-Based Carbon Fiber And Post-Treatment

The composition and structure of AR mesophase pitch werestudied by means of elemental analysis, FT-IR and XRD, the flow characteristics was observed and studied by the polarized light microscopy. The results show that mesophase was stripe-like fine fiber structure at 350℃. Considering the diameter of pitch fiber and continuity of spinning process, pitch fiber with excellent structures and properties was obtained at the spinning temperature of 350℃, spinning pressure 0.016MPa and spinning speed of 220m/min. In the spinning process, continuous spinning is about 5min.Mesophase pitch carbon fiber was obtained through melt-spinning, oxidization, carbonization from mesophase pitch. The oxidization process is studied by FTIR and TG-DSC. The results show that the surface of pitch fiber forms a stable oxygen-bridge structure, and the reaction occurred mainly in the 200-350℃.The influence of polysilonxane oiling agent to the pitch fibers oxidative oxidization process were studied by DSC, SEM and EDS. The results show that oiling agents make a good effect lower the electrostatic interaction among the fiber, reducing the mutual friction between the guide rollers and the fiber, effectively minimized the rate of surface defects of fiber. Meanwhile,the oiling agents could improve effectively collecting and separability of pitch fiber, making the regularity of the fibers markedly improved. The increasing of density of fibers may cause contacts of filaments, which would block the flow of gas in the bundle, retarding release of heat, which is generated by the oxidative oxidization, leading to fusion of filaments at the hot spots. Carbon fiber tensile strength is up to 1.36GPa at oxidization temperature of 290℃and phenyl-modified polysilonxane oiling agent concentration of 1%.The cross sections of oxidized fiber and carbon fiber were observed by the means of SEM. The results show that oxidized fiber and carbon fiber both exist defects, the defects cause marked skin-core structure in the cross section of fibers, the mechanical properties of carbon fiber will seriously be affected by skin-core structure. the microstructural evolution of pitch fiber in the oxidization, carbonization and graphitization process is studied by means of XRD and HRTEM. The results show that pitch fiber gradually change from short-range order graphite-like structure into long-range order graphite structure. As the carbonization temperature increased, the mechanical properties of carbon fiber was continuously improved. Carbon fiber tensile strength is up to 1.45GPa and modulus is up to 120GPa at oxidization temperature of 290℃and carbonization temperature of 1000℃.