Drop Breakup and Coalescence in Polymer Blends: The Effects of Concentration and Compatibilization

Sundararaj, Uttandaraman; Macosko, Chris

doi:10.1021/ma00112a009

Cited by 813 publications

(673 citation statements)

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“…The aqueous phase has a viscosity of 0.57 Pa·s and the continuum phase a viscosity of 2.08 Pa·s at 30 • C; the viscosity ratio is p = 0.27. The densities (g/cm 3 , at 30 • C) are 0.98 and 0.95 for the aqueous phase and the continuum phase, respectively. By using 2-propanol (aqueous solution) and trichlorobenzene (alkane mixture), the density of the two fluids can be adjusted to minimize sedimentation in the emulsion.…”

Section: Constituents and Preparation Of Emulsionsmentioning

confidence: 99%

“…In the literature, we find studies focused on the effects characterized by important processes, such as the role of coalescence-rupture [2][3][4] of drops or parameters (e.g., the viscosity ratio [5,6], the shear rate [7][8][9], and the volume fraction [10,11]). Nevertheless, much remains to be explored mainly because a complete understanding of the observed phenomena [12] is still lacking.…”

Section: Introductionmentioning

confidence: 99%

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Evolution of the Size Distribution of an Emulsion under a Simple Shear Flow

Leiva

Geffroy

2018

Fluids

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Understanding the rheology of immiscible liquids mixtures, as well as the role played by its micro-structures are important criteria for the production of new materials and processes in industry. Here, we study changes over time of the droplet size distributions of emulsions induced by slow shearing flows. We observe that the initial heterogeneous microstructure may evolve toward more complex structures (such as bimodal distribution) as a result of coalescence and rupture of droplets. These dynamic structures were produced using a flow cell made up of two parallel disks, separated by a gap of 100 µm. The steady rotation of the lower disk generates a simple shear flow of 2 of 15 r rates. Despite the possible relevance of the latter, here, we address f the emulsion at low shear rates and in the relevance to the rheology responds to the low, dimensionless time evolutions induced by slow ork.lished on the effects of the history of the shear rate (e.g., on the rop, or coalescence of quasi-equal size drops). The pioneering work t deformation of a single drop establishes experimentally that two etermine the drop deformation under a linear flow: the capillary rger capillary numbers induce larger drop deformations, and viscous r capillary number in order to deform significantly. n by Equation (1)e viscosity of the fluid matrix, the radius of the drop, the applied ion coefficient between phases, respectively. he two phases is given by Equation (2)perse fluid, and η m is the viscosity of the continuum fluid or matrix. nder flow (besides deformation of drops), other phenomena can alescence of drops [4], break up of drops [6], or capture of a rather larger drop [14]. When applying a larger shear rate to the emulsion, ed and are frequently the main source of the observed dynamical drops; although, each phenomenon depends most likely on different flows, coalescence of small, equal-sized drops is observed, and the rates of deformation, especially with low viscosity fluids. Research tions under shearing flows, even beyond a critical drop size (up droplets), are given in [15][16][17]. The growth of drops through the droplets-by a mechanism that appears to resemble an Oswald produced but requires a rather broad size distribution, including ing distributions of particles induced by flow have been observed as phenomena is less well documented. Here, we attempt to describe a low-shear-flow phenomena, which generally modifies the observed r complex and nonlinear manner.nism occurs mainly in the weakest of flows. During this process, end enough time in close proximity. Thus, a dimensionless time, τ, quired for a high probability of coalescence (or its efficiency) can betion of imposed flow of the experiment, while the shear rate,.γ, ions of drops of a given size. Please note that it is customary to ation measure, but here, we prefer to associate the inverse of this cy or efficiency of coalescence. Dimensionless deformation measures = 0.75 s −1 , during ∼ 400 s. After a brief rest time, this procedure was repeated by applying ...

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Section: Constituents and Preparation Of Emulsionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evolution of the Size Distribution of an Emulsion under a Simple Shear Flow

Leiva

Geffroy

2018

Fluids

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“…In order for the droplets to coalesce, a rupture must occur between two merging interfaces which, coupled with surface tension and hydrodynamic forces, leads to energetic barriers and non-trivial coalescence progression [1][2][3][4][5] . For complex fluids with partial positional and/or orientational order, the complexity of the coalescence reactions increases considerably 6 .…”

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confidence: 99%

Imprintable membranes from incomplete chiral coalescence

et al. 2014

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Coalescence is an essential phenomenon that governs the equilibrium behaviour in a variety of systems from intercellular transport to planetary formation. In this report, we study coalescence pathways of circularly shaped two-dimensional colloidal membranes, which are one rod-length-thick liquid-like monolayers of aligned rods. The chirality of the constituent rods leads to three atypical coalescence pathways that are not found in other simple or complex fluids. In particular, we characterize two pathways that do not proceed to completion but instead produce partially joined membranes connected by line defects-p-wall defects or alternating arrays of twisted bridges and pores. We elucidate the structure and energetics of these defects and ascribe their stability to a geometrical frustration inherently present in chiral colloidal membranes. Furthermore, we induce the coalescence process with optical forces, leading to a robust on-demand method for imprinting networks of channels and pores into colloidal membranes.

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“…The experiment was done in a journal bearing apparatus at low volume fraction to avoid coalescence. Sundararaj and Macosko (1995) show that the size of the dispersed phase may go through a minimum as rotor speed is increased. This behavior is attributed to elasticity acting as an additional restoring force on a drop.…”

Section: Viscositiesmentioning

confidence: 98%