2013
DOI: 10.1021/ma401833k
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Short-Term Flow Induced Crystallization in Isotactic Polypropylene: How Short Is Short?

Abstract: The so-called “short-term flow” protocol is widely applied in experimental flow-induced crystallization studies on polymers in order to separate the nucleation and subsequent growth processes [Liedauer et al. Int. Polym. Proc. 1993, 8, 236–244]. The basis of this protocol is the assumption that structure development during flow can be minimized and the rheological behavior, i.e., the viscosity, does not change noticeably. In this work we explore the validity of this assumption for short but strong flows and re… Show more

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Cited by 67 publications
(97 citation statements)
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“…Typically, going from the wall to the center of the product, one encounters first a quenched layer due to rapid cooling at the cold wall, then a highly oriented layer with shish-kebabs (typically created by shear rates in excess of $100 s À1 ), followed by a fine-grained layer with a high nucleation density (shear rates of $10-100 s À1 ) and finally a core with large spherulites [Housmans et al (2009b); van Meerveld et al (2004)]. The formation of the shear layer is commonly studied in isothermal channel flow experiments, with a combination of birefringence, x-ray diffraction, and ex-situ microscopy [Fernandez-Ballester et al (2012); Kumaraswamy et al (1999); Liedauer et al (1993); Ma et al (2013); Seki et al (2002)]. …”
Section: Introductionmentioning
confidence: 99%
“…Typically, going from the wall to the center of the product, one encounters first a quenched layer due to rapid cooling at the cold wall, then a highly oriented layer with shish-kebabs (typically created by shear rates in excess of $100 s À1 ), followed by a fine-grained layer with a high nucleation density (shear rates of $10-100 s À1 ) and finally a core with large spherulites [Housmans et al (2009b); van Meerveld et al (2004)]. The formation of the shear layer is commonly studied in isothermal channel flow experiments, with a combination of birefringence, x-ray diffraction, and ex-situ microscopy [Fernandez-Ballester et al (2012); Kumaraswamy et al (1999); Liedauer et al (1993); Ma et al (2013); Seki et al (2002)]. …”
Section: Introductionmentioning
confidence: 99%
“…The wellknown Kolmogorov-Avrami equation [56,57] accurately captures the crystallization kinetics of spherulites, even when their number density is strongly increased by flow [35,58]. However, for shish-kebab structures, in-situ XRD has revealed that the Avrami model often fails [49,[59][60][61].…”
Section: State Of the Artmentioning
confidence: 99%
“…This setup allows simultaneous probing of rheology, via pressure transducers positioned near both pistons, and of structure development through diamond windows in the slit placed halfway between both pistons. Part of the experimental data used for validation purposes has already been presented elsewhere [61]. The reader is referred to this paper for a full description of the experimental setup.…”
Section: Slit Flowmentioning
confidence: 99%
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“…That is to say, with the same shear strain, a shear flow at a high shear rate for a short time advances the crystallization process more than a shear flow at a low shear rate for a long time. [11][12][13] To be sure, more HMW chains and stronger flows generally help to obtain much more oriented crystals.…”
Section: Introductionmentioning
confidence: 99%