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Liu Y.,Donghua University | Yin L.,Jiangsu Hengli Chemical Fibre Co. | Zhao H.,Jiangsu Hengli Chemical Fibre Co. | Song G.,Jiangsu Hengli Chemical Fibre Co. | And 4 more authors.
Fiber Society's Spring 2015 Conference, in conjunction with the 2015 International Conference on Advanced Fibers and Polymer Materials: Functional Fibers and Textiles - Program | Year: 2015

Time-resolved synchrotron radiation small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) measurements were performed to study structure evolution of poly(ethylene terephthalate) (PET) industrial yarns during tensile deformation at 125°C. We found that both crystalline and amorphous phase were involved during the tensile process. WAXD data indicated that the crystallinity of the PET yarns decreased with increasing strain up to the fracture. The estimated crystallite size associated with the (010) reflection remained unchanged at strains under 15% and decreased quickly at strains from 15% to 32% (breaking point). The crystallite size associated with (-110) reflection decreased, while the crystallite size of (100) reflection nearly remained unchanged during the whole tensile process. SAXS data showed that the long period, crystalline and amorphous thickness increased with the increasing strain during tensile deformation. The enlargement of long period indicated that the lamellar structures of the yarns became loosely packed during the tensile deformation.


Liu Y.,Donghua University | Yin L.,Jiangsu Hengli Chemical Fibre Co. | Zhao H.,Jiangsu Hengli Chemical Fibre Co. | Song G.,Jiangsu Hengli Chemical Fibre Co. | And 4 more authors.
Polymer (United Kingdom) | Year: 2016

The evolutions in lamellar and fibrillar structures of poly(ethylene terephthalate) (PET) industrial fiber during taut-ends thermal annealing were investigated mainly using synchrotron radiation small-angle X-ray scattering (SAXS). Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) results indicated that high modulus and low shrinkage PET fiber (HMLS) had high crystallinity and perfect crystals, whereas high modulus and low elongation fiber (HMLE) possessed relatively low crystallinity and defective crystals. As annealing temperature raised, the original four-spot SAXS pattern gradually turned into the coexistence of two- and four-spot pattern, together with the enhanced scattering intensity. The analysis of the lamellar peaks showed that the annealing process had a significant influence on the thickness of crystalline and amorphous region, as well as the long period at 125, 200 and 240 °C. At the same time, the lateral size of the lamellae raised, whereas the lamellar surface inclination declined. In addition, the streak scattering across the beam stop was attributed to the fibrils. Results suggested that fibrils subjected to thermal effect tended to grow in longitudinal direction and became more oriented along the fiber axis. This study might help to predict structure and property changes at high temperatures for PET fiber and any other well oriented fiber that has a lamellar and fibrillar structure. © 2016 Elsevier Ltd


Liu Y.,Donghua University | Yin L.,Jiangsu Hengli Chemical Fibre Co. | Zhao H.,Jiangsu Hengli Chemical Fibre Co. | Song G.,Jiangsu Hengli Chemical Fibre Co. | And 4 more authors.
Journal of Applied Polymer Science | Year: 2015

Synchrotron radiation wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS) were performed to study the structures of four typical types of poly(ethylene terephthalate) (PET) industrial yarns. Three-dimensional structural models of the yarns and comprehensive insights into the process-structure-property relationships were gained. High spinning speed, low draw ratio, and high heat-setting temperatures lead to HMLS yarns with high crystallinity, high amorphous orientation, densely packed lamellar stacks, and a small tilting angle of crystalline lamellae. High draw ratio tends to result in PET industrial yarns with large long period and a large tilting angle of lamellae. Heat-setting process has a significant influence on the amorphous orientation and crystalline structures, such as crystallinity, crystallite size, as well as crystal grain number. Compared with other structure characteristics, amorphous orientation plays a more important role in determining the tenacity, initial modulus, part load elongation, ultimate elongation, as well as shrinkage of PET industrial yarns. The crystal grain number seems to have an effect on the initial modulus, while the long period influences the elongation of the yarns to some extent. In addition, the small tilting angle of crystalline lamellae may relate to the dimensional stability of PET yarns. © 2015 Wiley Periodicals, Inc.

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