Bundle‐like nucleation and longitudinal growth of fibrillar polymer crystals from flowing solutions

Pennings, A. J.

doi:10.1002/polc.5070590106

Cited by 157 publications

(34 citation statements)

References 77 publications

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“…These disc-shaped objects are edge-on views of PE single crystal lamellae and the peculiar morphology is similar to the classical polymer shish-kebab structures formed in an elongation/shear flow field. [46,47] The CNT/polymer system in this case was not under external flow during crystallization and it is the SWNT that induces nucleation of polymer chains on the SWNT surface. This observation serves as direct evidence that CNTs can promote heterogeneous nucleation of PE.…”

Section: Morphology Of Hdpe/swnt Nanocompositementioning

confidence: 98%

Morphology and Crystallization Behavior of HDPE/CNT Nanocomposite

Kodjie

et al. 2006

Journal of Macromolecular Science, Part B

162

104

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Section: Morphology Of Hdpe/swnt Nanocompositementioning

confidence: 98%

Morphology and Crystallization Behavior of HDPE/CNT Nanocomposite

Kodjie

et al. 2006

Journal of Macromolecular Science, Part B

162

104

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“…If the flow is strong enough, it can even create anisotropic crystalline structures, known as shish-kebabs. These structures, consisting of a fibrous backbone with lamellar overgrowth, were first recognized in notably stirred undercooled solutions [Pennings (1977); Pennings and Kiel (1965)], and later also in polymer melts [Keller and Mackley (1974)]. Author to whom correspondence should be addressed; electronic mail: g.w.m.peters@tue.nl…”

Section: Introductionmentioning

confidence: 98%

Modeling flow-induced crystallization in isotactic polypropylene at high shear rates

Roozemond

Drongelen

Zhu

et al. 2015

Journal of Rheology

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SynopsisA model is presented to describe flow-induced crystallization in isotactic polypropylene at high shear rates. This model incorporates nonlinear viscoelasticity, compressibility, and nonisothermal process conditions due to shear heating and heat release due to crystallization. Flow-induced nucleation occurs with a rate coupled to the chain backbone stretch associated with the longest mode relaxation time of the polymer melt, obtained from a viscoelastic constitutive model. Flow-induced nuclei propagate in flow direction with a speed related to shear rate, thus forming shish, which increase the viscosity of the material. The viscosity change with formation of oriented fibrillar crystals (known as "shish") is implemented in a phenomenological manner; shish act as a suspension of fibers with radius equivalent to the radius of the shish plus the attached entangled molecules? The model is implemented in a 2D finite element code and validated with experimental data obtained in a channel flow geometry. Quantitative agreement is observed in terms of pressure drop, apparent crystallinity, parent/daughter ratio, Hermans' orientation, and shear layer thickness. Moreover, simulations for lower flow rates are performed and the results are compared, in a qualitative sense, to experiments from literature. V C 2015 The Society of Rheology.

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“…Extensive research has been directed to the precise morphology of shish‐kebabs. It was found that the shishes consist of regions of extended chain crystals connected by fringe‐like amorphous regions, with kebabs formed by folded chain lamellae growing radially outward . A number of studies were directed to the minimal flow conditions needed to create these structures, expressed either in terms of stress, mechanical work, or backbone stretch .…”

Section: Introductionmentioning

confidence: 99%

Self‐Regulation in Flow‐Induced Structure Formation of Polypropylene

Roozemond

Drongelen

et al. 2014

Macromol. Rapid Commun.

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Flow‐induced structure formation is investigated with in situ wide‐angle X‐ray diffraction with high acquisition rate (30 Hz) using isotactic polypropylene in a piston‐driven slit flow with high wall shear rates (up to ≈900 s−1). We focus on crystallization within the shear layers that form in the high shear rate regions near the walls. Remarkably, the kinetics of the crystallization process show no dependence on either flow rate or flow time; the crystallization progresses identically regardless. Stronger or longer flows only increase the thickness of the layers. A conceptual model is proposed to explain the phenomenon. Above a certain threshold, the number of shish‐kebabs formed affects the rheology such that further structure formation is halted. The critical amount is reached already within 0.1 s under the current flow conditions. The change in rheology is hypothesized to be a consequence of the “hairy” nature of shish. Our results have large implications for process modelling, since they suggest that for injection molding type flows, crystallization kinetics can be considered independent of deformation history.

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Bundle‐like nucleation and longitudinal growth of fibrillar polymer crystals from flowing solutions

Abstract: This paper gives a brief account of the areas in which fibrillar crystals have been encountered and provides a mechanism for the formation of bundle‐like nuclei and the longitudinal growth of fibrillar polymer crystals from flowing solutions.

Cited by 157 publications

References 77 publications

Morphology and Crystallization Behavior of HDPE/CNT Nanocomposite

Morphology and Crystallization Behavior of HDPE/CNT Nanocomposite

Modeling flow-induced crystallization in isotactic polypropylene at high shear rates

Self‐Regulation in Flow‐Induced Structure Formation of Polypropylene

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