Structure devpelopment in the continuous laser-drawing process of poly(ethylene terephthalate) fibers was investigated with a time resolution of 0.2 ms by real time synchrotron X-ray diffraction and fiber temperature measurements. The (001′) and (003′) reflections of a quasi-smectic fibrillar structure were observed from 0.16 ms after necking, and the reflection intensity reached a maximum at around 0.3 ms after necking, when the elastic energy stored at the necking had been released. The d-spacing of the (001′) reflection decreased with increasing time, and the quasi-smectic fibrillar structure had a length of 70 nm and a radius of 7.0 nm. The crystallization induction time and crystallization rate were 0.3 ms and 1100 s–1 based on the fiber temperature profile and 0.6 ms and 1400 s–1 based on the equatorial reflection intensity profiles. In the azimuthal intensity profile under the 2θ/θ arrangement, a single meridional peak of the (003′) plane was observed, and it is considered that the quasi-smectic fibrillar structure oriented uniaxially along the fiber axis with an orientation factor of 0.986.

Because rapid and uniform laser heating can fix the neck-drawing point in continuous drawing of PTT fiber, we have successfully analyzed the fiber structure development in the continuous drawing process by in-situ measurement with a time resolution of less than 1 millisecond. In this study, we investigated fiber structure development for PTT around the neck point controlled with a CO 2 laser-heated apparatus during continuous drawing, through on-line measurements of WAXD, SAXS, and fiber temperature. Fiber temperature attained by laser radiation initiated a rise around -3 mm in relation to the neck point at 0 mm, and increased to about 90°C, which is past the 45°C T g for PTT. The instantaneous increase in fiber temperature continued with a vertical ascent, with plastic deformation around the neck point. The crystalline diffraction pattern was revealed initially at the elapsed time of 0.415 ms immediately after necking, and remained fairly constant with elapsed time. The ultimate crystalline diffraction pattern for a completely drawn fiber showed little difference from that at the initial stage. In PET a two-dimensionally ordered structure in the form of a mesophase was detected immediately after the necking, whereas in PTT the phenomenon was not observed. With elapsed time, the d-spacing of (002) plane decreased gradually due to transformation of the initial all-trans conformation into trans-gauche-gauche-trans conformation, and ultimately the PTT molecular chain could favorably adopt the trans-gauche-gauche-trans conformation. SAXS pattern immediately after the necking revealed an X-shape; the scattering intensity concentrated on meridian directions due to individual crystal development, and at 2 ms two-pointed scattering started to appear. Past 8 ms, the typical two-pointed scattering pattern was prominent and its intensity increased with elapsed time. Long period decreased with increasing elapsed time, but the crystallite size of meridian (002) plane hardly changed. The decrease in long period might be caused by chain relaxation in the amorphous region.

ABSTRACT:Structural development of isotactic polypropylene (iPP) fibers was analyzed in real time through in-situ WAXD/SAXS and fiber temperature measurements during CO 2 laser-heated drawing because the CO 2 laser irradiation can nearly fix the necking position on the running fiber. The in-situ WAXD/SAXS measurements were carried out with a high time-resolution of 0.4 ms. The as-spun iPP fibers of two different initial structures were laser-heat-drawn to a draw ratio of 6.5. For the drawing of PP fiber containing mesophase structure, diffraction from the oriented mesophase remained until an elapsed time of 1.0 ms, when oriented α-phase crystal started to form. Meanwhile, for the drawing of PP fiber containing both an α-phase and a mesophase structure, fragmented microcrystals were reorganized by orientation-induced crystallization before an elapsed time of 1.0 ms. The long period increased drastically with fragmentation, and decreased with reorganization. The long period was about 16 nm for both drawn fibers.--3

The structure development in the continuous laser-heated drawing process of poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) fiber was analyzed by in-situ X-ray diffraction measurement. Because of the rapid and uniform laser-heating, and the resultant steady-state nature of the necking-drawing, the structure development after the on-set of necking could be measured in the time resolution of several hundred microseconds. We found for the first time the temporal appearance of meridional (001') diffraction at several milliseconds after the on-set of necking indicating that the mesophase structure similar to the one reported for poly(ethylene terephthalate) was also formed in the initial stage of fiber structure development of PEN. The d-spacing of the (001') diffraction 1.230 ± 0.003 nm was shorter than the c-axis lengths of both Į and ȕ crystals. IntroductionPoly(ethylene 2,6-naphthalene dicarboxylate) (PEN), containing naphthalene ring in its backbone, possesses higher glass-transition temperature (T g ) and higher melting temperature (T m ) than those of poly(ethylene terephthalate) (PET). Due to the stiff molecular chain of PEN, it can be expected to give high-performance fibers having excellent physical properties for engineering uses.There have been studied on hot-drawing and cold-drawing processes in PEN fibers and films, [1,2] in which the drawability of amorphous PEN was reported to depend on molecular weight and strain rate. The structural changes in the neck-drawing of amorphous PEN films have been investigated through off-line measurement using synchrotron X-ray radiation, [1,3] which revealed the appearance of smectic order with a period of 1.25 nm corresponding to a chain repeat length associated with a sinusoidal conformation of the polymer chains. It was 5% shorter than the chain repeat length of a more extended Į-conformation. However, so far, there has been found no report about on-line characterization of structure development process with orientation-induced crystallization in PEN fiber and films.Several studies on the on-line characterization of the fiber structure development during the drawing have been conducted using simultaneous synchrotron radiation as well as laboratory X-ray generators for WAXD and SAXS. [4][5][6][7][8][9][10][11] Many of these studies concerned PET. Our research group has studied on the fiber structure development process in the continuous laser-drawing for PET and PTT fibers through on-line WAXD and SAXS measurements [9] with synchrotron radiation systems [10,11,12] . Quantitative analyses on the fiber structure development mechanism were accomplished by direct measurement in the vicinity of the neck-deformation point, in which drawing behavior, fiber temperature changes, and WAXD/SAXS were measured as a function of elapsed time after the neck-deformation. [9][10][11][12] The elapsed time, calculated from distance between measurement point and the neck-deformation point, is high accuracy because the neck point could be fixed within confined region by rapid and unifo...

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