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 len gths (0, 8, 30, and 45 mm). The molecular orientation of as-spun fiber s increased with the increase in the wire length at all the take-up ve locities examined. Along with the enhanced molecular orientation, the longer wire length led to the starting of orientation-induced crystall ization at lower take-up velocities. The structure of crystallized fib ers 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 di ameter of about 6 mm at the wire end. The spin-line temperature at thi s position was about 190 degrees C. The solidification of the spin-lin e occurred at positions much closer to the spinneret in comparison wit h ordinary high-speed spinning. These results show that high-speed spi nning with a wire inserted in the nozzle corresponds to a spinning pro cess operated at extremely low extrusion temperature using a nozzle wi th an extremely large diameter. From the starting of orientation-induc ed crystallization at lower levels of birefringence in comparison with ordinary high-speed spinning, the alteration of the inherent fiber st ructure that cannot be represented by birefringence was also suggested . (C) 1998 John Wiley & Sons, Inc.