Abstract:

In order to provide theory 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 showed 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 microcrystal-lites along the cross-section of CFs. Shear to the extrusive pitch melt further increasing, the IPc phase exhibited a perforative structure and the open crack reappear 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.

Key words: two-phase pitch, carbon phase structure, cross section structure