On the Kinetics of Polymer Crystallization in Opposite-Nozzle Flow

Janeschitz‐Kriegl, H.; Wippel, H.; Lin, Jia; Lipp, M.

doi:10.1007/s003970000136

Cited by 10 publications

(2 citation statements)

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“…Only the fluid elements on streamlines which closely approach the stagnation point in the center of the cross-slot flow are subjected to a large extensional deformation (Macosko 1996;Schoonen 1998;Verbeeten et al 2002). Hence, the requirements De s >1 and k>k*(T) are most easily fulfilled by these fluid elements, being in qualitative agreement with the position where the shish-kebab morphology develops (Mackley and Keller 1973;Janeschitz-Kriegl et al 2001;Swartjes 2001;Peters et al 2002;Swartjes et al 2003). The iPP melt considered by Swartjes (2001), Peters et al (2002), and Swartjes et al (2003) is characterized in the non-linear rheological regime, including chain stretching, and quantitatively described by a multi-mode version of the extended PomPom model (Verbeeten et al 2001(Verbeeten et al , 2002Verbeeten 2001;Swartjes 2001;Swartjes et al 2003).…”

Section: Extensional Flowssupporting

confidence: 50%

Towards a rheological classification of flow induced crystallization experiments of polymer melts

2004

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Section: Extensional Flowssupporting

confidence: 50%

Towards a rheological classification of flow induced crystallization experiments of polymer melts

2004

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“…Examples of these flows include the two roll mill, Frank and Mackley [9], Geffroy and Leal [10], the four roll mill, Crowley et al [11], Dunlap and Leal [12], McHugh et al [13], the (lubricated) converging flow with a free stagnation point, van Aken and Janeschitz-Kriegl [14], Macosko et al [15], the cross-slot device, Gardner et al [16], Miles and Keller [17] and the opposed jets device, Janeschitz-Kriegl et al [18], Keller et al [19], Mackay et al [20]. The basic principle of a stagnation flow is, in all cases, the same: two liquid streams are impinged.…”

Section: Introductionmentioning

confidence: 99%

Stress Induced Crystallization in Elongational Flow

Swartjes

Peters

Rastogi

et al. 2003

International Polymer Processing

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Stress-induced crystallization is studied in an extensional flow device (a cross-slot flow cell) for an isotactic Polypropylene (iPP) by measuring the micro-structure that develops after flow. Birefringence and Wide Angle X-ray experiments were performed. The birefringence experiments with flow below the melting temperature showed the occurrence of a fiber-like structure around the outflow centerline and, later in time, of 'streamlines'. The latter are explained by the influence of shear gradients close to the optical windows. The WAXS experiments also showed the fiber-like structure around the outflow centerline, having orientations in the (110), (040) and (130) reflections, with a width of about 80 lm. This dominance of the elongational flow around the stagnation line could not be observed in experiments with flow above and subsequent crystallization below the melting temperature. Structure development in this cell was numerically predicted using the Leonov and the extended Pompom (XPP) model. The oriented structures can be predicted. Moreover, process conditions are found with less influence of the (unwanted) shear gradients. Finally, it was concluded that the strain hardening behavior in the Leonov model over-estimates the first component of the Finger tensor, and thus the number of flow-induced nuclei. Therefore it is recommended to use the extended Pompom model as a more realistic basis for a quantitative flow-induced crystallization model. IPP_ipp1719 -2.4.03/druckhaus köthen FIBER AND FILM Intern. Polymer Processing XVIII (2003) 1  Hanser Publishers, Munich 53

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Industrial solidification processes in polybutene‐1. Part II—influence of shear flow

Braun¹,

Wippel²,

Eder³

et al. 2003

Polymer Engineering & Sci

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Following some early rudimentary results on shear‐induced crystallization of polybutene‐1 (1, 2), the present paper contains more detailed results. In the course of this work the origins of the highly oriented crystalline surface layers, as well known from injection molded samples, are more closely investigated. For the purpose, a special extrusion experiment is used, in which melts of various degrees of undercooling are moved through a duct of large aspect ratio. When, after the release of the pressure at the die entry, a quench of the duct to a temperature far below the melting point is delayed, a relaxation phenomenon is observed, in accordance with the experiences with i‐PP. From these experiments one learns that the leading parameter of the process is something like the mechanical work done per unit volume, and that the relaxation time increases with decreasing temperature much faster than the viscosity of the melt. The results are qualitatively in excellent agreement with our previously obtained results for polypropylene.

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On the Kinetics of Polymer Crystallization in Opposite-Nozzle Flow

Cited by 10 publications

References 0 publications

Towards a rheological classification of flow induced crystallization experiments of polymer melts

Towards a rheological classification of flow induced crystallization experiments of polymer melts

Stress Induced Crystallization in Elongational Flow

Industrial solidification processes in polybutene‐1. Part II—influence of shear flow

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