Effects of dimensions and regularity on the mechanical properties of the smectic phase formed during orientation-induced crystallization of poly (ethylene terephthalate)

A fibrillar-shaped metastable smectic phase forms during orientation-induced crystallization of poly(ethylene terephthalate). We investigated the effects of dimensions and regularity of the smectic phase on the mechanical properties by high-precision X-ray measurements. The drawing stress dependence was 76-168 MPa and the spinning speed dependence of 250-2000 m/min. The proportion, persistence length, and thickness of the smectic phase achieved their maximum values at 0.3-0.4 ms after necking. At this time g(II) also reached a minimum value of 3.7%-4.3%. The persistence length increased linearly with the natural draw ratio of as-spun fibers at less than 1500 m/min. The maximum values of the proportion, persistence length, and thickness showed no dependence on the drawing stress; however, the proportion and persistence length increased more rapidly. The increase of d-spacing with drawing stress led to an apparent elastic modulus of approximately 40 GPa for the oriented molecular bundle.ArticlePOLYMER.164:163-173(2019)journal articl

Ultra-SAXS observation of fibril-sized structure formation after the necking of poly(ethylene terephthalate) and poly(phenylene sulfide) fibers

Fibril-sized structures, which exhibit a density fluctuation of several tens to hundreds of nanometers, are important because they influence many properties of fibers and films, particularly the strength and thermal shrinkage of synthetic fibers. We analyzed the formation of fibril-sized structures after necking using ultra-small-angle X-ray scattering (USAXS), which enables observation of the void and craze formations. Continuous laser-heated drawing and undulator synchrotron radiation were adopted to measure the structural development of poly(ethylene terephthalate) (PET) and poly(phenylene sulfide) (PPS) fibers. Both fibers showed a clear increase in the meridional streak intensity just after necking and an increase in the equatorial streak after necking. These increases were distinctive for PPS. Moreover, a layer-lined streak appeared after necking only for PET. The intensity of the meridional streak increased with an increase in the draw ratio, whereas the intensity of the layer-lined scattering decreased with an increase in the draw ratio.ArticlePOLYMER JOURNAL.51(2):211-219(2018)journal articl

Ultra-SAXS observation of fibril-sized structure formation after the necking of poly(ethylene terephthalate) and poly(phenylene sulfide) fibers

Fibril-sized structures, which exhibit a density fluctuation of several tens to hundreds of nanometers, are important because they influence many properties of fibers and films, particularly the strength and thermal shrinkage of synthetic fibers. We analyzed the formation of fibril-sized structures after necking using ultra-small-angle X-ray scattering (USAXS), which enables observation of the void and craze formations. Continuous laser-heated drawing and undulator synchrotron radiation were adopted to measure the structural development of poly(ethylene terephthalate) (PET) and poly(phenylene sulfide) (PPS) fibers. Both fibers showed a clear increase in the meridional streak intensity just after necking and an increase in the equatorial streak after necking. These increases were distinctive for PPS. Moreover, a layer-lined streak appeared after necking only for PET. The intensity of the meridional streak increased with an increase in the draw ratio, whereas the intensity of the layer-lined scattering decreased with an increase in the draw ratio.ArticlePOLYMER JOURNAL.51(2):211-219(2018)journal articl