Structural and Morphological Studies of Isotactic Polypropylene Fibers during Heat/Draw Deformation by in-Situ Synchrotron SAXS/WAXD

Ran, Shaofeng; Zong, Xinhua; Fang, Dufei; Hsiao, Benjamin S.; Chu, Benjamin; Phillips, Robert

doi:10.1021/ma0016477

Cited by 179 publications

(167 citation statements)

References 36 publications

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“…As time elapsed, the broad diffraction became more asymmetric, and after 0.75 ms, the intensity of α-phase diffractions increased. This phenomenon in iPP-II partially corresponds to those reported by some researchers [26,27], who found that drawing at room temperature transformed the α-phase into the mesophase. The formation of the mesophase occurs through destruction of the lamellar crystalline phase; i.e., lamellar fragmentation, by pulling chains out from crystals.…”

Section: Fiber Temperaturesupporting

confidence: 87%

“…Several researchers suggested that the mesophase contains oriented bundles of helical chains with random helical hands [2,26] and is composed of microcrystals of the α-phase [34]. Accordingly, in iPP-I, we assumed that the helical chains of the initial mesophase most likely became oriented with elapsed time after necking, and after 1.0 ms, small-sized microcrystals were organized and formed the oriented α-phase.…”

Section: Waxd Analysesmentioning

confidence: 91%

“…Narrower MWD and higher IT developed only the lamellar stacking structure with c-axis crystallites oriented along the drawing direction detected at the deformation stage after necking, but for broader MWD and IT the oriented fibrillar structure was observed in addition to the lamellar stacking --4 structure. Ran et al [25,26] have reported that on-line studies on structural and morphological changes during the heating and drawing process of iPP fibers were carried out using synchrotron SAXS and WAXD techniques. The α-phase crystals were quite defective in the initial iPP fibers and were converted into the mesomorphic modification by drawing at room temperature.…”

Section: Introductionmentioning

confidence: 99%

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In-situ analysis of fiber structure development for isotactic polypropylene

Kang

Kim

Ikehata

et al. 2011

Polymer

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ABSTRACT:Structural development of isotactic polypropylene (iPP) fibers was analyzed in real time through in-situ WAXD/SAXS and fiber temperature measurements during CO 2 laser-heated drawing because the CO 2 laser irradiation can nearly fix the necking position on the running fiber. The in-situ WAXD/SAXS measurements were carried out with a high time-resolution of 0.4 ms. The as-spun iPP fibers of two different initial structures were laser-heat-drawn to a draw ratio of 6.5. For the drawing of PP fiber containing mesophase structure, diffraction from the oriented mesophase remained until an elapsed time of 1.0 ms, when oriented α-phase crystal started to form. Meanwhile, for the drawing of PP fiber containing both an α-phase and a mesophase structure, fragmented microcrystals were reorganized by orientation-induced crystallization before an elapsed time of 1.0 ms. The long period increased drastically with fragmentation, and decreased with reorganization. The long period was about 16 nm for both drawn fibers.--3

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Section: Fiber Temperaturesupporting

confidence: 87%

Section: Waxd Analysesmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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In-situ analysis of fiber structure development for isotactic polypropylene

Kang

Kim

Ikehata

et al. 2011

Polymer

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“…Q is already normalized with respect to the irradiated volume, because of the respective normalization of the measured intensity. Because the major fraction of the studied materials is semi-crystalline HDPE, the predominant contribution [24,[27][28][29][30] to the invariant…”

Section: Scattering Patternsmentioning

confidence: 99%

Nanostructure Evolution Mechanisms During Slow Load‐Cycling of Oriented HDPE/PA Microfibrillar Blends as a Function of Composition

Zeinolebadi

Stribeck

Sari

et al. 2012

Macro Materials & Eng

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Oriented precursors of MFCs consisting of HDPE and PA6 or PA12 are studied during strain‐controlled slow load‐cycling. In the PA6‐containing blends a strongly retarded nanostrain response is detected. Compatibilization induces nanostrain heterogenization. Stress fatigue is lower in the PA12 blends, but hardly decreased by the compatibilizer. Selective migration of the compatibilizer into a disordered semi‐crystalline fraction of the HDPE matrix can explain the findings. The semi‐crystalline HDPE entities in PA6 blends appear more disordered than in PA12‐blends. An analysis of the HDPE nanostructure evolution during cycling reveals epitaxial strain crystallization. Uncompatibilized PA6 blends cycled about high pre‐strain show plastic flow but nanoscopic shrinkage in the semi‐crystalline stacks. magnified image

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“…The objective of using eq 2 is only to obtain a qualitative evaluation of the oriented structures (detectable by transmission SAXS) induced by step shear. The unoriented component of the total intensity, I iso [ ], can be obtained with the halo method, 33 which can be described as follows. A series of azimuthal scans are extracted along the scattering vector initiated from the center of the SAXS image.…”

Section: Effect Of the Poss Concentration In Shearmentioning

confidence: 99%

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

Yang

Somani

et al. 2001

J Polym Sci B Polym Phys

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145

105

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Crystallization studies at quiescent and shear states in isotactic polypropylene (iPP) containing nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules were performed with in situ small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). DSC was used to characterize the quiescent crystallization behavior. It was observed that the addition of POSS molecules increased the crystallization rate of iPP under both isothermal and nonisothermal conditions, which suggests that POSS crystals act as nucleating agents. Furthermore, the crystallization rate was significantly reduced at a POSS concentration of 30 wt %, which suggests a retarded growth mechanism due to the molecular dispersion of POSS in the matrix. In situ SAXS was used to study the behavior of shear-induced crystallization at temperatures of 140, 145, and 150°C in samples with POSS concentrations of 10, 20, and 30 wt %. The SAXS patterns showed scattering maxima along the shear direction, which corresponded to a lamellar structure developed perpendicularly to the flow direction. The crystallization half-time was calculated from the total scattered intensity of the SAXS image. The oriented fraction, defined as the fraction of scattered intensity from the oriented component to the total scattered intensity, was also calculated. The addition of POSS significantly increased the crystallization rate during shear compared with the rate for the neat polymer without POSS. We postulate that although POSS crystals have a limited role in shear-induced crystallization, molecularly dispersed POSS molecules behave as weak crosslinkers in polymer melts and increase the relaxation time of iPP chains after shear. Therefore, the overall orientation of the polymer chains is improved and a faster crystallization rate is obtained with the addition of POSS. Moreover, higher POSS concentrations resulted in faster crystallization rates during shear. The addition of POSS decreased the average long-period value of crystallized iPP after shear, which indicates that iPP nuclei are probably initiated in large numbers near molecularly dispersed POSS molecules.

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Structural and Morphological Studies of Isotactic Polypropylene Fibers during Heat/Draw Deformation by in-Situ Synchrotron SAXS/WAXD

Cited by 179 publications

References 36 publications

In-situ analysis of fiber structure development for isotactic polypropylene

In-situ analysis of fiber structure development for isotactic polypropylene

Nanostructure Evolution Mechanisms During Slow Load‐Cycling of Oriented HDPE/PA Microfibrillar Blends as a Function of Composition

Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions

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