Effect of the Control of Polymer Flow in the Vicinity of Spinning Nozzle on Mechanical Properties of Poly(ethylene terephthalate) Fibers

Abstract

Abstract In the melt spinning of PET, effects of the variation of flow behavior in the vicinity of spinning nozzle on the mechanical properties of as-spun fibers and drawn fibers were investigated. The variation of flow behavior was introduced by the change of spinning nozzle diameter and by the irradiation of CO2 laser to the spin-line at a position immediately below the spinneret. The curve representing the correlation between strength and elongation at break of as-spun fibers shifted toward the upper-right direction by the applications of small diameter nozzle and laser irradiation, indicating that the toughness of as-spun fibers was improved. The two-stage continuous drawing of as-spun fibers with various draw ratios revealed that the correlation between strength and elongation of drawn fibers also shifted toward the upper-right direction by the application of small diameter nozzle and laser irradiation. In other words, improved toughness in the as-spun fibers was preserved in the drawn fibers. Accordingly, by the drawing of the as-spun fibers prepared by the combination of small-diameter nozzle and laser irradiation, high-strength and high-toughness PET fibers with the tensile strength of 1.68 GPa (12.1 cN/dtex) and the elongation at break of 9.1% was obtained. Numerical simulation of the melt spinning process incorporating the effects of nozzle diameter variation and laser irradiation heating indicated that the maximum Deborah number in the spin-line decreased by the applications of small diameter nozzle and laser irradiation heating. Accordingly, it was speculated that the variation of the state of molecular entanglement caused by the difference of polymer flow in the melt spinning process has significant effect on the mechanical properties of resultant fibers.