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

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 CO 2 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 hightoughness 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.

High-Strength PET Fibers Produced by Conjugated Melt Spinning and Laser Drawing

“…They speculated that the number of tensioned molecular chains can be decreased by the laser spinning of PET (Masuda et al, 2010). This argument was based on the coarse molecular dynamics simulation (Hotchi et al, 2007).…”

“…On the other hand, the higher thermal shrinkage stress indicates the higher drawing stress applied to the drawing process. The lower thermal shrinkage factor despite the higher drawing stress can be explained by a structure that emerged during conjugated melt spinning, having a large number of load-bearing molecular chains with a small stress distribution (Masuda et al, 2010).…”

“…In the 1990s, methods to produce high-molecular-weight PET fibers were researched (Ito et al, 1990;Huang et al, 1994). In recent years, a number of methods have been investigated to produce highstrength fibers by controlling the melt structure during the melt spinning process (Kikutani et al, 1996;Radhakrishnan et al, 1997;Jeon et al, 1998;Takarada et al, 2001;Masuda et al, 2004;Nakata et al, 2004;Masuda et al, 2010). Among these methods, the conjugated melt spinning process is used in the present study (Radhakrishnan et al, 1997;Nakata et al, 2004).…”

Melt-Spun Fibers for Textile Applications

“…In melt-spinning, drawing is the crucial step for extension and parallelization of macromolecules and crystallites along the filament axis, and thus achieving man-made fibers with a tensile strength about ten times higher than that of the as-spun filament [ 161 , 162 ]. Proper drawing results in row nucleated lamellae rather than spherulitic structures which would turn the fiber brittle [ 143 ].…”

Fiber structure development in PS/PET sea-island conjugated fiber during continuous laser drawing

“…Thus, to obtain high-strength fibers, a homogeneous chain network structure should be formed by melt spinning, followed by drawing to a high draw ratio. The term "melt structure control" [4][5][6][7][8][9][10][11] refers to methods of producing a homogeneous chain network structure, and bicomponent melt spinning has been investigated as one process of melt structure control. 5,9,11 The bicomponent melt spinning process, in which two types of polymer are simultaneously extruded from a spinneret, produces a unique fiber structure that is substantially different from that of a melt spun homopolymer.…”