Control of two-phase pitch precursor and microstructure of cross-section of carbon fibers
为给高性能碳纤维的结构设计提供理论参考,利用各向同性煤沥青(IPc)与中间相沥青形成二元不相容共混物的相分离结构,并利用筛网装置改变共混沥青的熔; 体流动状态,研究共混两相沥青的相结构对最终碳纤维结构的影响。结果表明:在共混前驱体中,掺杂的15%; IPc不足以抑制劈裂的形成;而使用15层筛网纺丝装置,促进微畴沿径向折叠排列,抑制了轴向劈裂的出现;进一步提高熔体受剪切程度,各向同性相形成贯穿; 的条带结构,纤维截面重新出现劈裂结构。30%的各向同性相抵抗了碳纤维中的裂纹扩展,碳纤维最终形成介于放射状和无规的截面形貌;使用50层筛网装置,; 纤维截面中出现类似的劈裂结构受到抑制一重新出现劈裂结构的演变过程。结果证实了相分离和筛网装置对中间相微畴在纤维中排布方式的协同影响作用。In order to provide academic reference for structure design of; high-performance carbon fibers (CFs),blends of composed isotropic (IPc); and mesophase pitches in various proportions were used as precursors for; CFs. A filter assembly was further used to disturb the melt flow during; the spinning of precursor fibers. The phase structure of; isotropic/mesophase incompatible blends on the microstructure of the; resultant CFs were studied. Results shows that 15% of IPc in the blended; precursor can not prevent the open crack along the carbon fiber axis,; while the split has been completely depressed in the carbon fibers when; spun with 15 layers of plain-weave, in which the IPc component exhibited; disorder oriented strips form to promote the zigzag connection among the; graphitic microcrystallites along the cross-section of CFs. Shear of the; extrusive pitch melt further increasing, the IPc phase exhibits a; perforative structure and the open crack reappears in the cross-section; of CFs. When the content of IPc is 30%,isotropic phase resists the; evolution of the open crack,and an intermediate morphology between; radial and random type is shown in the CFs. The similar evolution of the; open crack is shown in the cross-section of CFs when the 50 layers of; plain-weave is used. The results confirm the synergy effect of the; incompatible phase-separation of the blends and the filter assembly on; the arrangement of the graphitic microcrystallites along the; cross-section of CFs.