| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a flameproofed fiber for carbon fibers of high orientation, high strength and high grade by stabilizing operating conditions of an apparatus for production. SOLUTION: A precursor running by forming paths in a plurality of stages while performing drawing or shrinking in an oxidizing atmosphere is heat-treated. Tests for measuring the knot strength are carried out by forming a knot in a precursor single filament in the path in an optional stage, applying tension to the knotted single filament and measuring a change in stress while increasing the strain of the single filament. In the resultant stress-strain curve, the draw ratio corresponding to a point P of stress fall and re-rise at which the stress rises according to an increase in strain, then rapidly falls once, passes through the point P of stress fall and re-rise and further re-rises is taken as the upper limit of the draw ratio of the precursor in the path in the optional stage. The total draw ratio (total draw ratio in the flameproofing step) in the flameproofing step is 1.01-1.08 and the precursor is heat-treated to produce the flameproofed fiber. COPYRIGHT: (C)2006,JPO&NCIPI
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