Preparation And Study Of Pitch-based General Purpose Carbon Fibers From Ethylene Tar

As a superior carbon material, pitch-based carbon fibers (PCF) have been widelyused in a variety of specialized fields, such as aerospace, military, construction,transportation, chemical industry, sports and medical equipments, and compositematerials, etc. It is all based on their excellent properties, such as high tensile strengthand high modulus, low density and coefficient of thermal expansion, corrosionresistance and fatigue resistance, superior electrical and thermal conductivity.In this paper, besides the single method of air blowing and thermal condensation,a new oxidation-condensation combining method was taken to modulate the pitchprecursor for carbon fibers. Then measurement methods including group composition,elemental and thermal analysis, FT-IR, SEM and polarized optical micrographs wereused in this paper, and the influence of different methods of modulation on theperformance of pitches was discussed. Finally, the optimal method and technologywas choosed to prepare precursor for pitch-based carbon fibers: the ethylene tar pitchwas first air-blown under280℃for10h, and then thermal-condensed under380℃for3h in nitrogen. The spinnable pitch ABN-3synthesized by theoxidation-condensation combining method shows excellent properties: high softeningpoint (286℃), coking value (80.2%) and carbon content (94.61%), low H/C ratio(0.57) and superior thermal stabilities. Moreover, the ABN-3pitch was spun intofibers at315℃,0.4MPa and high drawing rate of660m/min, finally green fibers withuniform diameter (about14.8μm) and smooth surface were obtained.The parameters which affect the stabilization and carbonization were investigatedin this paper, such as temperature, residence time and the heating procedure. Theresult revealed that neither insufficient nor excessive oxidation will get carbon fiberswith excellent performance. In the stabilization, the optimal temperature range ofstabilization is260~320℃, the optimal residence time is60~120min, and theoptimal heating rate is1℃/min. In the cabonization, low heating rate can help theheteroatom to remove from the fibers gently, and reduce the escaping of carbon atom,so as to reach a higher carbonized yield. In addition, it’s helpful for pitch fiberstransform the stucture to semi-graphite.