Formation mechanism of shish in the oriented melt (I)—bundle nucleus becomes to shish

Yamazaki, Shinichi; Watanabe, Kaori; Okada, Kiyoka; Yamada, Koji; Tagashira, Katsuharu; Toda, Akihiko; Hikosaka, Masamichi

doi:10.1016/j.polymer.2004.12.009

Cited by 47 publications

(37 citation statements)

References 31 publications

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“…44 Subsequent studies of stress-induced crystallization of polyethylene elucidated this mechanism and revealed the detailed structure of these morphological units, which were called shish kebabs. [45][46][47][48][49][50][51][52] The detailed structure of polyethylene shish kebabs were revealed in recent studies, showing that the shish were sub-lm to $10 lm in length, $2-3 lm in diameter and contained $10-50 extended chain segments. 51,52 Also, a blend study revealed that mainly ultra-high molecular weight polyethylene chains ($5-6 Â 10 6 weight-average molecular weight) were involved in shish formation by a coil-stretch mechanism.…”

Section: Stress-induced Crystallizationmentioning

confidence: 99%

“…50 Similar observations were also found to apply to isotactic polypropylene. 49,50 This fact leads to the requirement for an explanation of the well-known difference in the effects of nucleating agents on polyethylene versus polypropylene. That is, nucleating agents have little or no effect on polyethylene crystallization, while they have a profound effect on that of polypropylene.…”

Section: Stress-induced Crystallizationmentioning

confidence: 99%

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Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Mirabella

2006

J Polym Sci B Polym Phys

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ABSTRACT:The HoffmanLauritzen theory of secondary, surface nucleation and growth was primarily relied upon for about 40 years after its introduction in about 1960 to rationalize the crystallization of flexible chain polymers into lamellar crystals. However, in about 1998, Strobl and coworkers introduced a different model for crystallization, based on the stagewise formation of lamellae. Two major components of this model were as follows: (1) the concept of the formation of a mesomorphic melt as a precursor to crystallization and (2) the control of the melting temperature range of lamellar crystals of homogeneous polyolefin copolymers by an inner degree of order or perfection rather than on the crystal thickness. The first concept is in disagreement with the HL theory and the second with the Gibbs-Thomson theory, which associates melting temperature with lamella thickness. In the present study, differential scanning calorimetry and atomic force microscopy were successfully employed to monitor the in situ quiescent crystallization of polyethylene homopolymer and copolymer. In the present study, evidence was not found to support the concept of lamellae with equal thickness melting over a broad temperature range. Some evidence was found that might be interpreted to support the concept of a mesomorphic melt as a precursor to crystallization. At present, the model promoted by Strobl and coworkers appears to be at an uncertain stage at which strong proof or disproof are not available. However, this alternative model has injected a new vitality into the study of crystallization of flexible chain polymers.

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Section: Stress-induced Crystallizationmentioning

confidence: 99%

Section: Stress-induced Crystallizationmentioning

confidence: 99%

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Mirabella

2006

J Polym Sci B Polym Phys

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“…In the case of a weak external field, an isotropic melt has the greatest volume. 4 Polymer chains must be ordered from the isotropic melt during crystallization. 5 However, this ordering is difficult because it is not easy for the entangled chains to slide along their chain axes and disentangle into an ordered parallel arrangement; therefore, amorphous areas remain in the solid.…”

Section: Introductionmentioning

confidence: 99%

Elongational crystallization of isotactic polypropylene forms nano-oriented crystals with ultra-high performance

Okada

Washiyama

Watanabe

et al. 2010

Polym J

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Although the large 'melt elongation' of polymers should significantly affect crystallization that controls the structure and properties of solids, it has been difficult due to technical reasons. In this paper, we succeeded in bulky elongational crystallization of isotactic polypropylene (iPP) by compressing the supercooled melt. The crystallization behavior and structure were observed by means of optical microscope, transmission electron microscopy (TEM) and X-ray scattering. When the elongational strain rate ( . e) surpassed a critical value ( . e*¼2Â10 2 s À1 ), the crystallization behavior, structure and physical properties underwent a discontinuous change. The crystallization rate increased by a factor as large as 10 6 , the crystallite lateral size decreased by a factor of 10 À3 to 20-30 nm and the morphology changed from well-known spherulites to a novel morphology of 'nano-oriented crystals (NOCs)'. These NOCs showed a high crystallinity (nearly equal to unity). The above results indicate that the polymer melt changed from isotropic to 'oriented melt' which accelerated nucleation and growth rates and induced NOC formation. NOCs showed ultra-high performance such as high tensile strength at break (D2.1Â10 2 MPa), comparable to that of metals, and a high thermal resistance (D176 1C). NOCs will be useful in a wide variety of applications and will contribute to efforts to construct a sustainable society by enabling the development of lightweight, recyclable materials. Polymer Journal (2010) 42, 464-473; doi:10.1038/pj.2010.35Keywords: crystallization; elongation; isotactic polypropylene; nano; SAXS; WAXS INTRODUCTION String-or chain-like molecules are major constituents of natural materials, as they have the remarkable characteristic of a high ability to self-organize. Because these molecules can form complex structures, they perform multiple functions and can carry information. The functions of these molecules and the information they carry have evolved over more than three billion years. Chain-like materials, called polymers, are now used in a variety of applications and have properties similar to those of the natural string-like molecules discussed above. Therefore, it is important for us to understand and control the behaviors of the structure formation of polymer.The molecular chain of a polymer in a melt or solution significantly changes its shape if an external field, such as an elongation, changes from weak to strong one, 1 which should significantly affect the crystallization behavior and properties of polymer solids. Therefore, the mechanism of structure formation and the expression of function of polymers under strong elongational fields are interesting problems

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“…The degree of crystallinity decreases likely due to increased spinline stress (increased drawing force) in the ultralow diameter filaments which may hinder crystallization, as suggested elsewhere [28]. Alternatively, it can be correlated with the balance between shear flow and cooling rate, where on the one hand a high shear rate prevents relaxation of the polymer chains, thus the induction time for crystallization is reduced [29,30], while on the other hand, in the shear region the chain segments tend to be more easily locked or frozen through a way in which they are first incorporated due to the higher cooling rate, which, like quasi-quenching, generates a lower degree of crystallinity [31]. As the filament gets even thinner the cooling rate increases rapidly, and despite the very high shear, there is a smaller crystalline fraction.…”

Section: Discussionmentioning

confidence: 99%

Crystalline structure and thermodynamic analysis of ultra‐low diameter VGCF‐polypropylene nanocomposite monofilaments

2014

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Nanocomposites of VGCF reinforced polypropylene monofilaments were created using melt compounding extrusion. The monofilament diameter and VGCF loading were varied to characterize the effects of spinline stress and imposed confinement on material properties, including crystalline structure and thermodynamic behavior. A correlation was found between spinline stress, degree of confinement, depression of the melting temperature, and changes in crystallite dimensions and orientation. POLYM. COMPOS., 37:1641–1649, 2016. © 2014 Society of Plastics Engineers

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Formation mechanism of shish in the oriented melt (I)—bundle nucleus becomes to shish

Cited by 47 publications

References 31 publications

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Elongational crystallization of isotactic polypropylene forms nano-oriented crystals with ultra-high performance

Crystalline structure and thermodynamic analysis of ultra‐low diameter VGCF‐polypropylene nanocomposite monofilaments

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