Fiber structure development in PS/PET sea-island conjugated fiber during continuous laser drawing

The effect of draw ratio, molecular weight, and sea-island conjugated spinning with a polystyrene component on the fiber structure development of PET during laser drawing was analyzed by in-situ measurements with a 0.1 ms time resolution using an ultra-high luminance X-ray beam generated from a synchrotron equipped with an undulator. The fiber temperature increased from 120 °C to 160–220 °C during the structure development process. By drawing the higher molecular weight PET to a higher draw ratio, a larger amount of fibrillar smectic mesophase formed just after the onset of necking, and a more highly oriented crystal formed after the extinction of the smectic mesophase. Accordingly, fibers with higher strength and higher thermal shrinkage stress were obtained. On the other hand, by conjugated spinning with a PS component, the fiber temperature increased along with an increase in the drawing stress, but the stress applied to the PET component should have decreased. The amount of smectic mesophase formed by the conjugated-spinning process was drastically decreased, and no crystallization induction time was observed, unlike the other cases. Crystallization, particularly the growth of a lamellar crystal, was also promoted. Moreover, a higher Young's modulus, a higher yield stress, and a higher shrinkage stress were observed for the conjugated-spun and drawn fibers. Therefore, the fibrillar smectic mesophase seems to block the formation of the lamellar crystal. Furthermore, the resultant fibrillar structure tends to result in a higher strength, but a relatively lower modulus and yield strength of the fiber.ArticlePOLYMER. 79:37-46 (2015)journal articl

Effect of draw ratio on fiber structure development of polyethylene terephthalate

Fiber properties are decided by its structure, and the structure are mainly formed in the fiber drawing process. In this study, the effects of the draw ratio on the fiber structure development of polyethylene terephthalate after continuous neck-drawing were investigated using simultaneous WAXD/SAXS measurements. Low-oriented amorphous as-spun fibers were drawn to a draw ratio of 3.0-4.5, at which the fiber can be stably neck drawn. WAXD and SAXS images were obtained up to 2.0 ms when the structure was mainly developed. The smectic (0010) diffraction intensity and long period increased with increasing draw ratio up to 4.2, and a larger (0010) diffraction d-spacing was observed at a draw ratio of 4.5. The results suggest that more fibrillar structures were formed with increasing draw ratio up to 4.2, and more constrained molecular bundles were formed at a draw ratio of 4.5. A larger amount of constrained fibrillar structures can bear a greater tensile force in tensile tests, therefore the drawn fibers have higher tensile strengths. (C) 2017 Elsevier Ltd. All rights reserved.ArticlePOLYMER.116:357-366(2017)journal articl

Effect of melt spinning conditions on the fiber structure development of polyethylene terephthalate

The effects of spinning conditions on fiber properties are not well explained by the fiber structures because the birefringence, crystallinity, and SAXS patterns are often similar. In this study, the effects on the fiber structure development of polyethylene terephthalate after necking was analyzed by simultaneous WAXD/SAXS measurements. An X-shaped SAXS pattern was observed for all fibers drawn at the minimum draw ratio. In contrast, by drawing under a drawing stress of 100 MPa, the strong diffraction of the smectic phase and an obviously larger long period less than 1 ms after necking were observed for fibers spun at 500-1500 m/min, while almost no smectic phase was observed for fibers spun at 2000 m/min. A higher crystallization rate and clear draw ratio dependence of crystallization rate were also observed for the fiber spun at 2000 m/min. The clear differences in structure development can explain their differences in tensile strength and thermal shrinkage. (C) 2017 Elsevier Ltd. All rights reserved.ArticlePOLYMER.116:367-377(2017)journal articl

Radiosensitivity of pimonidazole-unlabelled intratumour quiescent cell population to γ-rays, accelerated carbon ion beams and boron neutron capture reaction.

[Objectives] To detect the radiosensitivity of intratumour quiescent (Q) cells unlabelled with pimonidazole to accelerated carbon ion beams and the boron neutron capture reaction (BNCR). [Methods] EL4 tumour-bearing C57BL/J mice received 5-bromo-2′-deoxyuridine (BrdU) continuously to label all intratumour proliferating (P) cells. After the administration of pimonidazole, tumours were irradiated with γ-rays, accelerated carbon ion beams or reactor neutron beams with the prior administration of a [10]B-carrier. Responses of intratumour Q and total (P+Q) cell populations were assessed based on frequencies of micronucleation and apoptosis using immunofluorescence staining for BrdU. The response of pimonidazole-unlabelled tumour cells was assessed by means of apoptosis frequency using immunofluorescence staining for pimonidazole. [Results] Following γ-ray irradiation, the pimonidazole-unlabelled tumour cell fraction showed significantly enhanced radiosensitivity compared with the whole tumour cell fraction, more remarkably in the Q than total cell populations. However, a significantly greater decrease in radiosensitivity in the pimonidazole-unlabelled cell fraction, evaluated using a delayed assay or a decrease in radiation dose rate, was more clearly observed among the Q than total cells. These changes in radiosensitivity were suppressed following carbon ion beam and neutron beam-only irradiaton. In the BNCR, the use of a[10]B-carrier, especially L-para-boronophenylalanine-[10]B, enhanced the sensitivity of the pimonidazole-unlabelled cells more clearly in the Q than total cells. [Conclusion] The radiosensitivity of the pimonidazole-unlabelled cell fraction depends on the quality of radiation delivered and characteristics of the [10]B-carrier used in the BNCR