High-speed Melt Spinning of Polyethylene terephthalate with Periodic Oscillation of Take-up Velocity

Abstract

High-speed MeltSpinningofPolyethylene terephthalatewithPeriodicO scillation of Take-up VelocityToi nvestigatethe non-steady-statem elts pinning behavior, take-upvelocity wasvaried periodicallyin the high-speed melt spinning process of polyethylene terephthalateand the timecoursechangesof velocity and diameterof the spin-line were measured simultaneously.Anumericalsimulation programfor the non-steady-statemeltspinning process wasalsodeveloped. Inthe range of relativelylowt ake-upvelocities,experimental results and results of numericalsimulation of the non-steadystatem elts pinning process showed afairagreement,in that the amplitude fort he variation of the reciprocalo fthe crosssectionalareaa nd thatfort he variation of velocity of the spin-line hadalinearr elation. Anincreaseinthe frequencyof velocity oscillation led toaless significantv ariation in the thickness of as-spunf ibers.Onthe otherhand,therewasa phaseshiftbetween the oscillationoftake-upvelocity and that of the reciprocalofcross-sectionalareaof the spin-line atthe pointof take-up. When take-upvelocity wasincreased,starting of the orientation-induced crystallization along withthe occurrenceofneck-like deformation caused some characteristicbehaviors suchass ignificantincreasesin the amplitudesof velocity and diameterfluctuationsatac ertain region in the spin-line.Suchbehaviors could bereproduced in the numerical calculation byincorporating the stress dependentchange of solidificationtemperature. Itwasalsorevealed thatthe orientation-induced crystallization hast he effectof stabilizing the spinning system. 1IntroductionTherehavebeen manyresearcheson the steady-statemeltspinning process including structuralanalysisof as-spunf ibers, modeling and numericalsimulation of the process,and on-line measurements of the spin-line [1,2].Onthe otherhand,numberof publicationson the non-steady-statem elts pinning process islimited although itisimportantfort he analysisof the stability of the process.Clarification of the mechanismforthe developmentof instability in the meltspinning process isindispensable forthe improvementof the dimensionaland structural uniformity of as-spunfibers.Inaddition,knowledge on the instability of melts pinning process maybeapplied fort he production of fibers withcontrolled non-uniformity.Governing equationsdescribing the non-steady-statem elt spinning process werep roposed by Kase and Matsuo [3,4]. Numericalanalysesof thesee quationsw ereapplied fort he melts pinning process withstep-wiseo rperiodicc hangesof quenching air[5to7].Mechanismo fd raw-resonance,a ni nherentinstability of the meltspinning process appearing asthe periodicc hange of the fibert hickness,wasalsoi nvestigated widelyusing theseequations [8to12].Investigationson the applicability of thesef undamental equationsthrough directcomparison of the results of numerical simulation and on-line measurementaren oteasy tocarry out becauseo fthe difficulty in conducting detailed on-line measurements of the non-steady-statemeltspinning process.Inthis study,withthe intention of introdu...

Transient solutions of dynamics in fiber spinning and film casting accompanied by flow-induced crystallization

“…Although the same extensional deformation is occurred at the same drawdown ratio, compared with no-crystallization cases, the feasible deformation length is shortened and the rate of deformation is highly increased because of the reduced spinline residence time. Contrary to low-speed spinning case of our study, TAKARADA et al [8] concluded that flow-induced crystallization has the stabilizing effect in high-speed spinning system, because the severe fluctuation of spinning variables near the solidification position by the crystallization has been attenuated by the further necking formation. It is noted here that stability analysis of the high-speed spinning with necking now becomes one of the challenging theoretical issues.…”

“…Although the both cases are stable ones, the case with crystallization emerges as less stable, taking more time converging to the steady state, showing that the spinline crystallization destabilizes the iPP spinning process. Sensitivity analysis as experimentally conducted by TAKARADA et al [8] clarifies the effect of crystallization on the process stability. Under the same periodically oscillating take-up velocity condition (ω=100) as an input, the amplitude of oscillating cross-sectional area at take-up with crystallization is larger than that without crystallization case as shown in Fig.3.…”

Sensitivity of spinning process with flow-induced crystallization kinetics using frequency response method

“…In the case without neck-like deformation, the system becomes more sensitive as increasing drawdown ratio, corresponding with stability results [3] (Fig. 8) and sensitivity experiments [29]. However, the system becomes somewhat less sensitive at r=140 (x=0.960) just before the crystallinity is fully developed.…”

“…In this paper, take-up velocity and take-up area have been primarily adopted as an input and an output, respectively, based on the experimental method by Kikutani group [29].…”