: In the melt spinning of high molecular weight poly(ethylene terephthalate), spinline immediately below the spinning nozzle was heated by irradiating the CO 2 laser with the intention of controlling the physical and mechanical properties of resultant fibers. In comparison with the fibers prepared without the laser irradiation, as-spun fibers obtained with laser irradiation showed higher elongation at break and higher tenacity. Higher elongation was attributed to lower tensile stress in the spinline caused by the increase of spinline temperature. Drawn fibers were produced from thus prepared as-spun fibers at various draw ratios. When the drawn fibers with similar elongation at break were compared, fibers prepared with the laser irradiation showed steeper increase in the stress-strain curve in the region of low strain, and showed higher tenacity as a result. On the whole, plot of the relation between tenacity and elongation at break of each fiber shifted toward higher tenacity and higher elongation in case of fibers prepared with the laser irradiation, indicating that the toughness of the fibers were improved. Numerical simulation of the melt spinning process incorporating the effect of laser irradiation suggested that temperature increase by the laser irradiation was at most about 70 degree in the spinning conditions adopted in this study. It was also confirmed that the heating of the spinline immediately below the spinneret led to steeper decrease of spinline diameter in the region near the spinneret, and reduction of strain rate and decrease of tensile stress in the region of lowered spinline temperature. These changes in the thinning behavior of the spinline were speculated to be the origin of the changes in the mechanical properties of laser irradiated fibers.
Injection molding of thin-wall parts with microscale surface grooves of polypropylene (PP) and cyclo-olefin copolymer (COC) were performed for this study. Effects of cavity thickness and process conditions on processability, surface replication, and higher-order structure of the molded products were evaluated. Surface replication and optical anisotropy of molded products were analyzed using a polariscope, a polarizing optical microscope, SEM, and a confocal laser scanning microscope. Optical anisotropy in the vicinity of the gate was higher than that at any other position; also, optical anisotropy increased with decreased cavity thickness. The replication property at the center area was more pronounced than those of the flow end and the gate vicinity. The distribution of the replication ratio inside the product decreased with increasing mold temperature. Results showed that the replication properties were correlated closely with skin-shear layer thickness inside the products, and that the replication ratio was lower for greater thickness of the skin-shear layer.
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...
Micromolding with micro-scale surface features of hexagonal boron nitride (h-BN) / polypropylene (PP) composites with different h-BN component was performed to improve molded parts’ heat diffusivity and processability. Effects of h-BN content and process parameters on processability, higher-order structure, and microscale surface patterns of molded parts were analyzed using SEM, WAXD, SPM, and confocal laser scanning microscopy. The replication ratio of the microscale surface pattern and flow length of composite molded parts was improved by compounding the h-BN filler. The replication ratio of the microscale surface pattern near the flow end became greater than 1.0 because of deformation of surface patterns during de-molding. The replication ratio and shape of surface patterns of molded parts were improved with the increase of the h-BN component. The h-BN platelet oriented inside surface micro-features; skin-shear-core structures were well observed in the molded parts.
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