The initial stage of fiber structure development in the continuous neck-drawing of amorphous poly(ethylene terephthalate) fibers was analyzed by in-situ wide-angle x-ray diffraction, small-angle x-ray scattering, and temperature measurements. The time error of the measurements (< 600 μs) was obtained by synchrotron x-ray source and laser irradiation heating. A highly ordered fibrillar-shaped two-dimensional (smectic-like) structure was found to be formed less than 1 ms after necking. By analyzing its (001') and (002') diffractions, the length of the structure 60-70 nm were obtained. A three-dimensionally ordered triclinic crystal began to form with the vanishing of the structure around 1 ms after necking. The amount and size of the crystal were almost saturated within several milliseconds of necking, during which time a mainly exothermic heat of crystallization was also observed.

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.

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