Amorphous poly(ethylene terephthalate) (PET) can be stretched at low tension without causing any observable crystallization at temperatures above the glass-transition temperature. The resulting increased length with no measurable change in orientation is called superdrawing. Superdrawing of hollow PET fibers in the circumferential direction was demonstrated earlier. This behavior is accompanied by an increase in fiber voids caused by a combination of air expansion and water permeation. The present work describes efficient techniques for superdrawing in the circumferential direction only. The process develops large void (>65%) fibers starting from standard 15% void spun supply. It is not possible to obtain such large voids in the longitudinal direction in low denier-per-filament fibers via direct melt spinning. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 123–127, 2005
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