Structural changes of acrylic fibers of various compositions by stretching were investigated, and the relation between the fibrillar structure of as-spun fibers and the stretching behavior was studied.
The results obtained are as follows:
(1) In the case of stretching as-spun fibers with gross fibrils and large pores, the degree of the orientation of the crystallite increases remarkably with the increase in stretch ratio, accompanied with the fibrillar orientation, while the apparent density of the fibers does not change appreciably. On the other hand, in the case of stretching as-spun fibers with fine fibrils and small pores, the orientations of both fibrils and crystallite proceed gradually, and the apparent density of the fibers increases, At the same time, fibrils recombine with or separate from one another during stretching.
(2) The larger the specific surface area of as-spun fibers, the lower is the degree of orientation of crystallite after the stretching, and the specific surface area is related linearly to the degree of orientation. This relation holds good not only in the case of DMSO-H
2O spinning bath, but also in the case of ordinary wet spinning of acrylic fibers, This fact shows that the stretching behaviors of acrylic fibers are determined exclusively by the fibrillar structure formed during coagulation.
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