The Preparation And Stabilization Process Of Isotropic Pitch-based Carbon Fiber

In this paper,fluid catalytic cracking slurry oil that removed impurities in the laboratory was used as raw material.The feasibility of isotropic pitch-based carbon fiber used precursor pitch produced by thermal polycondensation-solvent extraction and thermal polycondensation-solvent extraction-vacuum distillation was tested,various solutions were used during solvent extraction,in order to adjust softening point of precursor pitch.The spinnability of precursor pitch was tested through comparison of the fiber breakage number and diameter of as-spun fiber among melt-spinning,and thus,optimal precursor pitch was selected.Melt-spinning was used to produce as-spun fiber,subsequently,stabilization and carbonization.The temperature,heating rate and maintaining time of stabilization to determine optimal stabilization condition were studied.The produced precursor pitch,thermal polycondensation under 380、390、400°C for 10 h in ambient pressure and after extracting with n-heptane,had a softening point of 220、 230、240°C respectively,polymeric pitch under 390°C,10 h,ambient pressure possessed better spinnability and relatively high yield rate.We used hybrid solution with different volume ratio of n-heptane and toluene between the process of solvent extraction.Aromatic components with less degree of condensation while polycondensation temperature was lower,380°C、390°C.The spinnable pitch yield rate was decreased with toluene content,by contrast,yield rate of spinnable pitch was increased with polycondensation temperature rising.Insoluble fraction of hybrid solution was processed through vacuum distillation.Yield rate of vacuum distillation residue descended with toluene content in hybrid solution,and softening point of residue increased with vacuum distillation temperature,but the yield rate was reduced.The temperature of vacuum distillation no more than one of prepared polymeric pitch,to bypass the further condensation of aromatic components existed.Different parameters among stabilization were compared,such as,temperatures,heating rates and retaining time at the ultimate stabilization stage,to find those effects on mechanism performance of carbon fiber.Temperature higher than 270°C,more rapid heating,residence time longer than 30 min allowed as-spun fiber tend to excess stabilization,result of oxygen uptake rising and impairing carbon fiber’s mechanism performance.Slower heating rate brought appropriate stabilization due to even oxygen diffusion between the inner and outer surfaces of carbon fibers.The best conditions of stabilization in the work was observed by analysing the TG measurement of spinnable pitch.At the steps of stabilization,the temperature was increased from room temperature to 180°C with 1°C/min heating rate,then gradually,reaching 270°C at a rate of 0.5°C/min and remaining 30 min.Finally,the isotropic pitch-based carbon fiber with even diameter of 11 um had average tensile strength,modulus and elongation at break of 0.9GPa,36.69 GPa and 2.2% respectively,following carbonization at 1000°C for 5min.