The Structure Dependent Physical and Rheological Properties of The Mesophase Pitches

Abstract

The effects of the structural characteristics of mesophase pitches on the rheological and physical properties were investigated in terms of temperature and shear. M-AR, polymerized from naphthalene with the HF/BF3 catalyst, was naphthenic and methylene-rich structure and T-MP, thermally condensed from coal tar, was aromatic structure. T-MP gave higher intensity ratio of D-band to G-band than M-AR in Raman analysis. Liquid crystalline morphology of M-AR was marbled texture and that of T-MP was schlieren texture. Shear initially applied to the pitches promoted the formation of the liquid crystalline domain. Molecular unstacking of M-AR proceeded gradually whereas that of T-MP occurred abruptly at particular temperature with increasing temperature in wide angle X-ray diffraction. Differential scanning calorimetry detected the molecular unstacking of T-MP near 350oC. M-AR and T-MP in nematic phase became biphase and isotropic phase in dynamic viscosity curves, respectively. The apparent viscosity curves followed the Onogi and Asada curve, which was proposed for liquid crystalline polymers.