Mechanism of Structural Formation by Uniaxial Deformation in Amorphous Poly(ethylene terephthalate) above the Glass Temperature

Online wide‐angle X‐ray diffraction/small‐angle X‐ray scattering measurements for the CO2‐laser‐heated drawing of poly(ethylene terephthalate) fiber

“…This indicates that only a part of amorphous phase is highly oriented. This scattering should be the same as that observed for PET film by Mahendrasingam et al 20,[22][23][24] and Kawakami et al 31,32 Crystal diffraction appeared abruptly 20 ms after necking. It is not observed at all in the 17 ms diffraction image, and becomes clear in the 30 ms image.…”

“…For the drawing process, most on-line measurement studies fall into one of two categories; batch drawing under small strain rate [20][21][22][23][24][25][26][27][28][29][30][31][32] , and draw ratio dependence of continuous drawing [33][34][35][36] . In both cases, x-ray diffraction images are taken at a fixed position.…”

Structural development of poly(ethylene terephthalate) during uniaxial stretching above the glass‐transition temperature: Study of the statistical influence of the stretching variables

“…All of the other conditions gave rise to an amorphous halo, although in some cases, the intensity profile seemed to concentrate at the equator region; this suggested the existence of some polymer chain orientation in the stretching direction and the presence of some content of mesophase, as reported elsewhere. 39,43,45,47,49 Although we expected to have amorphous halos in the C1, C2, C3, and C4 conditions, because the material was stretched to only 1.6Â, C6 and C8 were stretched to a much higher stretching level (2.1Â) and still presented amorphous halos. This result showed that the temperature had an important role in the structural development of the sample, and in these cases, it hindered the strain-induced crystallization mechanism of PET because of a possible competing mechanism between chain elongation due to mechanical deformation and chain relaxation due to the elevated temperature.…”

“…When a crystal diffraction peak was detected in the meridional profile [e.g., at (À103) at 2y ¼ 26.6 reflection], its area contribution was excluded (e.g., C7). 43 The subtraction of the crystalline and amorphous fractions from the total area of the equatorial profile was considered to be proportional to the amount of the mesophase. The mass fraction of the individual phases was taken to be the ratio of the area for each phase to the total area of the equatorial profile.…”

“…They suggested a three-stage structural development mechanism consisting of (1) orientation (molecular orientation occurred because of strong molecular interactions), (2) nucleation (nuclei appeared as a result of molecular orientation and at a given level of strain, the number of nuclei was fixed; this formed a network structure that was responsible for strain hardening), and (3) a growth stage (crystallization developed through the growth process). Kawakami and coworkers, 43,45 by in situ WAXS and small-angle X-ray scattering (SAXS), provided new insights to the subject by determining that the first stage, also called the orientation stage, would take place until strain hardening was initiated (plastic deformation region) and involved the formation of a mesophase with highly oriented chain segments. In this stage, the oriented mesophase increased continuously with the applied strain without the formation of crystals.…”