Disclosed is an industrialized
polyimide fiber drafting method. The method includes that a certain deniers of
polyimide yarn sheets with uniform tension are placed in a four-
part type hotbox environment and clamped by a rubber roller, under a certain feeding speed, the
yarn sheets achieve a certain multiple drafting through a speed difference between a front
drafting machine and a rear
drafting machine, and the four-
part type hotbox is a combination of a prehearing section hotbox, a
superheated steam humidifying section hotbox, a high temperature drafting hotbox and a setting hotbox. During the process of the
fiber treatment, the temperature changing gradient is reasonable, the
impact thermal load which is stressed on the fibers is small, and the probability that the
yarn sheets generate broken filaments is remarkably reduced. The fibers are subjected to
superheated steam humidifying treatment before the high temperature drafting, the
static electricity in the yarn sheets is eliminated, the drafting force of the same number of fibers is reduced by 25%, the draft multiple is increased by 30%, and the strength of the fibers is increased 40%. After the
polyimide fibers are subjected to the drafting and high temperature setting, the
internal stress of the polyimide fibers is eliminated, the stability of the
fiber structure is improved, and the shrinking rate of the polyimide fibers is maintained about 2%.