Rheo-optic flow-induced crystallisation of polypropylene and polyethylene within confined entry–exit flow geometries

Scelsi, Lino; Mackley, M. R.

doi:10.1007/s00397-008-0278-z

Cited by 26 publications

(21 citation statements)

References 27 publications

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“…The mechanical properties of the final products are significantly dependent upon the degree of crystallization and types of crystals formed and therefore optimization of any polymer process requires a good understanding on how flow influences crystallization (McHugh 1995;Eder et al 1990;Kornfield et al 2002;Janeschitz-Kriegl 2003;Scelsi and Mackley 2008;Kumaraswamy et al 1999). In particular, the orientation of the crystals in elongational and shear flows affect the crystallization and thus the mechanical properties (Gelfer and Winter 1999).…”

Section: Introductionmentioning

confidence: 99%

Flow-induced crystallization of high-density polyethylene: the effects of shear and uniaxial extension

Derakhshandeh

Hatzikiriakos

2011

Rheol Acta

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The effects of shear, uniaxial extension and temperature on the flow-induced crystallization of two different types of high-density polyethylene (a metallocene and a ZN-HDPE) are examined using rheometry. Shear and uniaxial extension experiments were performed at temperatures below and well above the peak melting point of the polyethylenes in order to characterize their flow-induced crystallization behavior at rates relevant to processing (elongational rates up to 30 s −1 and shear rates 1 to 1,000 s −1 depending on the application). Generally, strain and strain rate found to enhance crystallization in both shear and elongation. In particular, extensional flow was found to be a much stronger stimulus for polymer crystallization compared to shear. At temperatures well above the melting peak point (up to 25 • C), polymer crystallized under elongational flow, while there was no sign of crystallization under simple shear. A modified Kolmogorov crystallization model (Kolmogorov, Bull Akad Sci USSR, Class Sci, Math Nat 1:355-359, 1937) proposed by Tanner and Qi (Chem Eng Sci 64:4576-4579, 2009) was used to describe the crystallization kinetics under both shear and elongational flow at different temperatures.

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Section: Introductionmentioning

confidence: 99%

Flow-induced crystallization of high-density polyethylene: the effects of shear and uniaxial extension

Derakhshandeh

Hatzikiriakos

2011

Rheol Acta

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“…The main advantage of this device over rotational and capillary rheometers is that the machine can be operated at high shear rates and pressures, while slip is prevented due to confinement of the material in the set-up. Interchangeable geometries (capillary, slit, cross-slot) equipped with appropriate windows allow for optical and X-ray diffraction measurements during and after flow (Mackley et al, 2000;Lele et al, 2002;Collis and Mackley, 2005;Coventry and Mackley, 2008;Hassell and Mackley, 2008;Scelsi and Mackley, 2008). The MPR is described in more detailed in Section 2.1.…”

Section: Introductionmentioning

confidence: 99%

A Design to Study Flow Induced Crystallization in a Multipass Rheometer

Housmans

Balzano

Santoro

et al. 2009

International Polymer Processing

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The design and performance of a flow geometry for the multipass rheometer (MPR) is described, creating an experimental setup to study in-situ and ex-situ structure and morphology development with a proper control over the processing conditions and shear history. The slit used is equipped with diamond windows, to combine flow with different experimental techniques, such as optical microscopy (OM), birefringence and X-ray scattering. In this paper we present preliminary results, obtained on isotactic polypropylene, that demonstrate the possibilities of this device for more extended future research. The focus is on the in-situ birefringence measurements of crystallization and the relation with the final morphology.

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“…This effect is illustrated in Fig. 46 [105] where the time evolution of FIC within a shallow slit is shown and FIC continues after the cessation of flow. It should be noted that in a shallow slit, FIC can occur at both the side and front facing glass walls of the geometry.…”

Section: Flow Induced Crystallisation (Fic)mentioning

confidence: 89%

“…The MPR offered the ability to release the initial pressure at different rates and the data shown in Fig. 52 illustrates that the Reprinted with permission from [105] pressure release rate does influence the growth kinetic. This feature was not included or predicted by the model and indicates that the initial boundary conditions for the growth process do depend on variables such as pressure release rate and other factors.…”

Section: Foamingmentioning

confidence: 93%