Evaluation of the utility of isotropic pitches as solvent components of spinnable mesophase pitch precursors for highly graphitizable functional carbon materials

Spinnable mesophase pitch (SMP) is an important graphitizable precursor for high-performance carbon materials. Generally, SMPs show fully developed anisotropic texture, and the pitches contain isotropic contents more than 30 wt%, which plays the role of solvent for the mesogenic components in the lyotropic liquid crystalline system of the pitch. Here, we prepared SMP by blending the mesogenic components of AR mesophase pitch with various isotropic pitches to evaluate the usability of isotropic pitches as solvents. The mesogenic components were prepared by tetrahydrofuran fractionation of AR mesophase pitch. Isotropic pitches with a softening point of 140–220 °C were prepared separately by simple heat treatment of slurry oil (SO) and coal tar pitch (CTP). SMPs were prepared by thermal blending of the above mentioned mesogenic components and isotropic pitches in various blending ratios. CTP-derived isotropic pitch showed better solvent performance than a SO-derived pitch in terms of anisotropic texture. SMP prepared by blending of the mesogenic components and CTP-derived isotropic pitch with a softening point of 180 °C at the ratio of 4/6 (w/w) showed almost 100% anisotropic texture; the carbon fiber derived from the pitch showed tensile strength of 2.7 GPa and Young's modulus of 470 GPa after graphitization at 2,800 °C.