Effects of shear flow and viscosity difference on phase separation

Ōnuki, Akira

doi:10.1007/bf01441904

Cited by 22 publications

(9 citation statements)

References 38 publications

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“…This observation is contrary to what was observed in the case of the quiescent blend, in which the domain size of the dispersed phase increases with increasing temperature. This phenomenon was also observed in binary fluid mixtures under shear (27) in which a larger droplet volume fraction was obtained when the quench depth decreased. The above effect becomes more evident when the sheared samples are compared to quiescent samples at the same temperature.…”

Section: Quiescent Conditionssupporting

confidence: 59%

An investigation of shear‐induced mixing in the PSAN/PMMA blend

Papathanasiou

Higgins

Soontaranun

1999

Polymer Engineering & Sci

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We investigate experimentally the effect of steady‐state simple shear flow on the miscibility of a 60–40 poly(styrene‐co‐acrylonitrile) with poly(methyl‐methacrylate) (PSAN/PMMA) blend. Thin disks, containing 60% w/w PSAN, are thermoformed from blend pellets made by mixing PSAN and PMMA granules in a co‐rotating, fully‐intermeshing twin‐screw extruder. These disks are sheared at constant shear rate in a cone‐and‐plate mechanical spectrometer at fixed temperatures within the quiescent two‐phase region. At the end of each shearing experiment the sample is quenched and its morphology investigated first visually for optical transparency (cloudiness being an indicator of a phase‐separated blend) and then using transmission electron microscopy (TEM). Results indicate that upon imposition of a shear rate as low as 0.1s−1 the 60–40 blend remains miscible even at temperatures up to 7K within the (quiescent) two‐phase region. These observations are in agreement with theoretical predictions of the phase diagram under shear, based on the concept of a modified Gibbs free energy of mixing. The TEM results concerning the morphology of the phase‐separated blends are also discussed.

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Section: Quiescent Conditionssupporting

confidence: 59%

An investigation of shear‐induced mixing in the PSAN/PMMA blend

Papathanasiou

Higgins

Soontaranun

1999

Polymer Engineering & Sci

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“…The change and enlargement of the phase structure observed in 70/30 PC/PMMA might be attributed to the evolution of the liquid–liquid phase separation by stretching at 160 °C, which was above the T g s of both component polymers. Since PC/PMMA blends are partially miscible and are suggested to exhibit an LCST type phase diagram [48,49], the evolution of the liquid–liquid phase of separation might be caused by shifting the LCST phase diagram to a lower temperature by stretching [60] and the orientation-induced phase separation [46,47,61].…”

Section: Resultsmentioning

confidence: 99%

“…The durometer D hardness increased from 80 to 83 by blending 5% of PMMA [45]. The segregation of PMMA might be attributed to the orientation-induced phase separation resulting from variations in viscosity, due to composition fluctuations [46,47]. A PC/PMMA blend is partially miscible and is suggested to exhibit a lower critical solution temperature (LCST) type phase diagram, in which liquid–liquid phase separation occurs at a temperature above the LCST [48,49].…”

Section: Introductionmentioning

confidence: 99%

Structural Evolution of Two-Phase Blends of Polycarbonate and PMMA by Simultaneous Biaxial Stretching

Kobayashi

Saito

2018

Polymers

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We investigated the structural evolution of the two-phase blends of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) at various blend compositions by simultaneous biaxial stretching, using optical microscopy and SEM observation. The spherical PMMA domains and PC matrix of 30/70 PC/PMMA were enlarged uniformly at the all in-plane direction, while the anisotropic-shaped co-continuous structure in 50/50 PC/PMMA was deformed to a crosshatched structure by the in-plane bimodal orientation. In 70/30 PC/PMMA, the phase inversion was found to occur by simultaneous biaxial stretching; that is, the spherical PMMA domains were changed to a crosshatched matrix by the in-plane bimodal orientation due to coalescence of the PMMA domains during the stretching. Owing to the phase inversion, the surface hardness estimated by the pencil hardness test became harder, from 2B to 2H, increasing the strain from 1.0 to 2.0.

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“…It allows them to make a broad range of structures for a given composition. [4][5][6][7] In addition, the structure formation could be followed by measuring the effect of the shear rate on the rheological properties, such as viscosity and normal forces. 8,9 These studies indicated that the structure formation is a result of interactions present in the dispersion in relation to the shear stress applied.…”

Section: Introductionmentioning

confidence: 99%

Creating Novel Structures in Food Materials: The Role of Well-Defined Shear Flow

et al. 2008

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Structure formation in food materials is influenced by the ingredient properties and processing conditions. Until now, small structural elements, such as fibrils and crystals, have been formed using self-assembly, while processing was applied to create relatively large structures. The effect of self-assembly under flow is rarely studied for food materials, but it is widely studied for non-food systems. The use of well-defined flow, often simple shear, turned out to be essential to study and control the structure formation process in foods as well. This observation encouraged us to develop a number of different shearing devices that allowed processing of biopolymer systems under simple shear flow. This paper reviews our main findings. In the case of protein fibrillization, the shear rate was found to control the growth rate as well as the properties of the fibrils formed. In the case of dough processing, simple shear flow made the product more process tolerant and induced gluten migration. The use of shear flow for dense caseinate dispersions led to hierarchically structured and fibrous material. Based on the presented results, we conclude that introducing simple shear flow in food structuring processes can lead to a much broader range of structures, thereby better utilizing the full potential of food ingredients.

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Effects of shear flow and viscosity difference on phase separation

Cited by 22 publications

References 38 publications

An investigation of shear‐induced mixing in the PSAN/PMMA blend

An investigation of shear‐induced mixing in the PSAN/PMMA blend

Structural Evolution of Two-Phase Blends of Polycarbonate and PMMA by Simultaneous Biaxial Stretching

Creating Novel Structures in Food Materials: The Role of Well-Defined Shear Flow

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