Effect of metallic wire inserted in nozzle in high-speed melt spinning of poly(ethylene terephthalate)

High‐speed melt spinning of poly(ethylene terephthalate) was performed using a spinning nozzle with an inserted metallic wire of various lengths (0, 8, 30, and 45 mm). The molecular orientation of as‐spun fibers increased with the increase in the wire length at all the take‐up velocities examined. Along with the enhanced molecular orientation, the longer wire length led to the starting of orientation‐induced crystallization at lower take‐up velocities. The structure of crystallized fibers obtained at low speeds can be characterized by high crystallinity and relatively low molecular orientation. From the on‐line measurement of the diameter and temperature profiles of the spin line with the 30‐mm metallic wire, it was revealed that the spin‐line had a maximum diameter of about 6 mm at the wire end. The spin‐line temperature at this position was about 190°C. The solidification of the spin‐line occurred at positions much closer to the spinneret in comparison with ordinary high‐speed spinning. These results show that high‐speed spinning with a wire inserted in the nozzle corresponds to a spinning process operated at extremely low extrusion temperature using a nozzle with an extremely large diameter. From the starting of orientation‐induced crystallization at lower levels of birefringence in comparison with ordinary high‐speed spinning, the alteration of the inherent fiber structure that cannot be represented by birefringence was also suggested. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 665–674, 1998