The invention discloses a method for preparing
polyacrylonitrile carbon
fiber protofilament by dry and wet methods. The method comprises the steps of
polymerization, demonomerization and defoaming,
filtration, coagulation, washing and drafting, oiling densification, steam drafting,
heat setting and
drying. Three-level coagulating baths at the temperature of between 10 DEG C below zero and 70 DEG C and with
dimethyl sulfoxide with concentration of 10 to 60
mass percent are adopted in the coagulation step, and the first coagulating bath contains aqueous
ammonia accounting for 0.05 to 1 percent of the
mass of the first coagulating bath; and a
spinning head is subjected to 1.5 to 5 times positive drafting in the first coagulating bath, and the drafting is 0 in the second and third coagulatingbathes. According to the method for preparing the
polyacrylonitrile carbon
fiber protofilament, the
spinning process is stable, the broken filament is little, the
spinning speed is high, the spinningis stable, the prepared protofilament has few defects, the density is not less than 1.180g / cm<3>, and the tensile strength is not less than 7cN / dtex. The protofilament can be prepared into a high-performance carbon
fiber with tensile strength of more than 4.9GPa and
elastic modulus of between 260 and 280GPa by high-temperature
carbonization.