Preparation of carbon fiber from isotropic pitch containing mesophase spheres

Naphthalene based synthetic isotropic pitch was found to give spinnable precursors which carried 10-100 μm anisotropic spheres of 45 and 50 vol% in the isotropic matrix, when the pitch was heat-treated at 375 and 380°C for 20 and 23 hours, respectively. The spun fiber was stabilized and carbonized into a carbon fiber, which showed anisotropic belts running along the fiber axis, suggesting that both anisotropic spheres and isotropic matrix are deformed to align within the nozzle. The structure and mechanical properties of the carbon fibers, thus prepared, were examined under microscopes and by mechanical testing.