Effects of chemical structure of mesogenic components on the mechanical properties of mesophase pitch-based carbon fiber

Carbon fiber (CF) is a high-performance material with a wide range of industrial applications due to its light weight and excellent mechanical properties. Mesophase pitch (MP)-based CF (MPCF) is a type of CF with superior mechanical properties. Precursor MP is complex, with multiple components, and recent studies have revealed its lyotropic liquid crystal properties. The solvent components in the lyotropic liquid crystal are important for facilitating the technically challenging melt spinning of MP, and the concentration of mesogenic components influences the mechanical properties of the resulting MPCF. However, the effects of different mesogenic components on the physicochemical characteristics of MP and the mechanical properties of MPCF remain unclear. This study was performed to investigate how the characteristics of mesogenic components in MP affect the mechanical properties of MPCF. Precursor MPs were prepared using mesogenic components extracted from three different naphthalene-based, coal tar-based, and petroleum-based parent MPs, combined with a specific solvent component at the same concentration. The structure of the mesogenic components influenced MP formation with the solvent component. Mesogenic components containing naphthenic ring structures exhibited high affinity and stacking properties with the solvent component. Mechanical evaluations revealed that the tensile strength and Young's modulus of the resulting graphitized fibers varied depending on the properties of the mesogenic components. Notably, mesogenic components containing naphthenic ring structures led to the formation of larger crystallites in the graphitized fibers, enhancing their tensile strength (maximum tensile strength of 4.0 GPa) and Young's modulus (maximum Young's modulus of 618 GPa).