Manufacturing spinnable mesophase pitch using direct coal extracted fraction and its derived mesophase pitch based carbon fiber

Spinnable mesophase pitch with high pitch yield of more than 50 wt% was successfully prepared using direct bitumen coal extracted fraction through the three-step process of hydrogenation, N₂ blowing heat treatment, and thin-layer evaporation. The prepared mesophase pitch was smoothly spun to the fibrous form and could be converted into mesophase pitch-based carbonized and graphitized fibers through the usual oxidative stabilization, carbonization, and graphitization. The prepared mesophase pitch based carbon fibers showed typical random transversal structures with mechanical performances, tensile strengths of 1.83 GPa and 3.00 GPa, Young's moduli of 133 GPa and 450 GPa, and elongation properties of 1.37% and 0.68% after heat treatments at 1000 °C for 30 min and 2800 °C for 10 min, respectively. The relatively high-molecular-weight and well-developed polynuclear aromatic molecular structure of hypercoal is the likely reason for the high mesophase pitch yield. The meaning of each preparation processes, hydrogenation, N₂ blowing heat treatment and thin layered evaporation, was discussed in detail. We anticipate that the success of high-yield mesophase pitch manufacturing using hypercoal as raw material will be an important key to innovatively reduce the production cost of mesophase pitch-based carbon fiber.