Effect of drawing stress on mesophase structure formation of poly(ethylene 2,6-naphthalene dicarboxylate) fiber just after the neck-drawing point

The structural development of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) fibers was analyzed by in situ X-ray diffraction and fiber temperature measurements. The PEN fiber was drawn continuously under three drawing stresses, where the neck-drawing point was fixed accurately by CO2 laser irradiation heating. The developed crystal structures of the drawn fibers depended on the drawing stresses, that is, only the alpha-crystal was obtained under a drawing stress of 148 MPa, an alpha-rich mixed crystal was obtained for 54 MPa, and a beta-rich mixed crystal was obtained under 23 MPa stress. Fiber containing over 70% beta-crystal was obtained in the third case. Orientation-induced crystallization rates (K) and crystallization induction times (t(0)) were estimated for the three drawing stresses: K = 2210 s(-1) and t(0) = 0.5 ms for 148 MPa, K = 940 s(-1) and t(0) = 1.0 ms for 54 MPa, and K= 655 s(-1) and t(0) = 4.0 ms for 23 MPa. In addition, the drawing stress acted as a definitive influence not only on the resulting crystal form but also on the chain conformation of the mesophase structure. The d-spacing of the (001') diffraction increased with drawing stress, and the longer (001') spacing generated the alpha-crystal while the comparatively shorter (001') spacing yielded the beta-crystal. The d-spacings of 1.27 and 1.23 nm for the drawing stresses of 148 and 23 MPa, respectively, were somewhat shorter than the c-axis lengths of the alpha- and beta-crystals of 1.32 and 1.27 nm, respectively.ArticlePOLYMER. 53(19):4272-4279 (2012)journal articl

Effects of dimensions and regularity on the mechanical properties of the smectic phase formed during orientation-induced crystallization of poly (ethylene terephthalate)

A fibrillar-shaped metastable smectic phase forms during orientation-induced crystallization of poly(ethylene terephthalate). We investigated the effects of dimensions and regularity of the smectic phase on the mechanical properties by high-precision X-ray measurements. The drawing stress dependence was 76-168 MPa and the spinning speed dependence of 250-2000 m/min. The proportion, persistence length, and thickness of the smectic phase achieved their maximum values at 0.3-0.4 ms after necking. At this time g(II) also reached a minimum value of 3.7%-4.3%. The persistence length increased linearly with the natural draw ratio of as-spun fibers at less than 1500 m/min. The maximum values of the proportion, persistence length, and thickness showed no dependence on the drawing stress; however, the proportion and persistence length increased more rapidly. The increase of d-spacing with drawing stress led to an apparent elastic modulus of approximately 40 GPa for the oriented molecular bundle.ArticlePOLYMER.164:163-173(2019)journal articl

Ultra-SAXS observation of fibril-sized structure formation after the necking of poly(ethylene terephthalate) and poly(phenylene sulfide) fibers

Fibril-sized structures, which exhibit a density fluctuation of several tens to hundreds of nanometers, are important because they influence many properties of fibers and films, particularly the strength and thermal shrinkage of synthetic fibers. We analyzed the formation of fibril-sized structures after necking using ultra-small-angle X-ray scattering (USAXS), which enables observation of the void and craze formations. Continuous laser-heated drawing and undulator synchrotron radiation were adopted to measure the structural development of poly(ethylene terephthalate) (PET) and poly(phenylene sulfide) (PPS) fibers. Both fibers showed a clear increase in the meridional streak intensity just after necking and an increase in the equatorial streak after necking. These increases were distinctive for PPS. Moreover, a layer-lined streak appeared after necking only for PET. The intensity of the meridional streak increased with an increase in the draw ratio, whereas the intensity of the layer-lined scattering decreased with an increase in the draw ratio.ArticlePOLYMER JOURNAL.51(2):211-219(2018)journal articl

In situ study of fiber structure development of poly(butylene terephthalate) in a continuous laser-heated drawing process

The structural development of poly(butylene terephthalate) (PBT) fibers was analyzed using in situ wide angle X-ray diffraction and fiber temperature measurements during CO2 laser-heated drawing, in which the necking position on the running fiber could be fixed by CO2 laser irradiation. The measured parameters were determined as functions of the elapsed time after necking with a time resolution of 0.3 ms. The as-spun PBT fibers, which exhibited a low-oriented alpha-crystalline structure, were drawn to a draw ratio of 5 using laser heating. The (001') reflection, which indicates a quasi-smectic fibrillar structure, was not observed before crystallization in contrast to measurements of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalene dicarboxylate) (PEN). The alpha-crystal was transformed into an oriented beta-form crystal at the necking position, and the developed beta-crystallites exhibited increased size and altered orientation <2 ms after necking. The fiber temperature increased rapidly at around T-g, and the rearrangement of the beta-crystal primarily occurred as the fiber's temperature rose from 100 to 160 degrees C. The oriented beta-crystal of the drawn fiber transformed into the oriented beta-crystal when the drawing tension was released. Polymer Journal (2012) 44, 1030-1035; doi: 10.1038/pj.2012.65; published online 18 April 2012ArticlePOLYMER JOURNAL. 44(10):1030-1035 (2012)journal articl

Structure and Mechanical Properties of Poly(trimethylene terephthalate) Fibers Obtained by CO2 Laser Drawing and a Secondary Contact Heater Drawing

1CO2 laser drawing heats a running fiber homogeneously and rapidly without contact by laser irradiation and develops a necking in a fixed location. As-spun fibers of bio- and chemo-based poly(trimethylene terephthalate) (PTT) were drawn to draw ratio (DR) of 3.5-5.5 and 3.5-4.8 by CO2 laser-heated drawing, respectively, which was taken as the first drawing. Secondarily the first-drawn fibers were drawn to total draw ratio (TDR) as high as possible by direct contact heater drawing of 150 degrees C, which attained TDR 5.60-5.70 and 5.40-5.46 for bio- and chemo-based PTT fibers, respectively. Drawing stress in situ measured in the two-steps drawing increased roughly proportional to draw ratio, and for bio-based PTT was higher than for chemo-based one when compared at the same DR and TDR. We investigated in this study the structure and mechanical properties of the drawn PTT fibers by wide angle X-ray diffraction (WAX])), birefringence, thermo-mechanical property, and tensile property. The typical WAXD pattern of PTT crystal was observed with orientation-induced crystallization by the two-steps drawing. But, the meridional reflections become blurred and their intensities decrease with increasing draw ratio and by the second drawing. The transverse crystallite sizes, along the normal direction of (010) plane, increased transversely but the longitudinal sizes, along the normal direction of (002) plane decreased longitudinally as draw ratio increased for chemo-based PTT, whereas for bio-based PTT, the crystallite size change with draw ratio was the same trend with the chemo-based by the first drawing but the crystallite became much smaller transversely and longitudinally by the second drawing. By the azimuthal intensity profile, the crystal orientation factor obtained from (010) plane increased, while that from (002) plane decreased with the total draw ratio. The birefringence was a constant value 0.07 with no dependence on draw ratio by two steps drawing, which is over twice a reported intrinsic birefringence of PTT crystal, 0.029 [12]. Also, Young's modulus held an almost constant value of 2.3-2.6 GPa by the two stages drawing, which is very closed to 2.59 GPa, the theoretical modulus of PTT crystal.ArticleSEN-I GAKKAISHI. 69(6):107-117 (2013)journal articl