Modification of petroleum-derived mesophase pitch by blending naphthalene-derived partially isotropic pitches

Two kinds of naphthalene-derived, partially isotropic pitches were blended into the mesophase pitch from decant oil to modify the molecular association of the mesophase pitch and performances of its derived carbon fibers. A pitch (C-65: anisotropic content 60%) could be blended up to 50% into the 100% mesophase pitch, maintaining its complete anisotropy. Another pitch of P-77, which contained more soluble portions of smaller molecular weight, could be accommodated up to only 20%, although its anisotropic content was much the same as that of C-65. Blending partially isotropic pitch with the petroleum-derived 100% mesophase pitch intensified both aromatic and aliphatic resonances at around 130 and 30 ppm, respectively, in high-temperature 13C-NMR. Blending isotropic pitches with the petroleumderived 100% mesophase pitch lowered the melting viscosity to allow at spinning better alignment of the mesophase constituent molecules along the fiber axis than those of parent mesophase pitch, leading to higher orientation of the graphite layers, crystalline size and Young's modulus of resultant carbon fibers. The blending of 20%–50% naphthalene-derived, partially isotropic pitch with the 100% petroleumderived mesophase pitch certainly enhanced the oxidation reactivity of whole mesophase pitch to shorten the time for complete stabilization at the same level as naphthalene-derived 100% mesophase pitch. Blending of only 20% naphthalene, partially isotropic pitch with the parent mesophase pitch certainly improved the Young's modulus, orientation of the crystallines along the fiber axis and crystalline size of the resultant carbon fibers. It should be noted that there was a dominant partner or synergistic influence of the blended naphthalene, partially isotropic pitch in their improvement. The chemical and physical functions of blended isotropic components are discussed.