Kyukoshi method preparation

Figure 6. Flow charts for the preparation of fiber-spinning pitches by the Gundai (dormant mesophase) and Kyukoshi methods.

Figure 7. Relations between softening points, quinoline-insoluble contents, and mesophase contents of precursor pitches prepared by the Gundai and Kyukoshi methods. The volume percentage of mesophase is indicated by the numbers adjacent to some points.

The mechanical properties as a function of heat treatment temperature are shown in Figure 9 for fibers prepared by the Kyukoshi method. Fiber heat-treated to 2000°C or higher have strengths above 3GPa (435 kpsi) and tensile moduli of the order of 500 GPa (72 Mpsi). The present authors now believe that, in the near future, it will be possible to produce carbon fiber of equivalent properties by selection of suitable raw pitch materials and by development of specialized pretreatment procedures for the pitch to replace the extensive hydrogenation technique described here. 

Figure 8. Viscosity of mesophase pitches prepared by the Kyukoshi method, with schematic microstructures of fibers spun at temperatures in the range of 300 to 400°C.

Figure 9. Mechanical properties, as a function of heat treatment temperature, of carbon fibers spun from mesophase pitch prepared by the Kyukoshi method.

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