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Emulsion homogeneous model

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. [Pg.360]

On the other hand, suppose that each of these polymer molecules is isolated into different particles, and that each particle contains one radical, as shown in Fig. 17b. If the radical causes the polymer transfer reaction, the partner must be the polymer molecule that happens to exist in the same particle (so it cannot partner a larger polymer molecule that exists in a different polymer particle). As a consequence, the expected size of the polymer molecule attacked by a radical is smaller for emulsion systems than for the homogeneous model shown in Fig. 17a. [Pg.98]

Homogeneous Models. The basic assumption in these models is that the emulsion is a continuum, single-phase liquid that is, its microscopic features are unimportant in describing the physical properties or bulk flow characteristics. It ignores interactions between the droplets in the emulsions and the rock surface. The emulsion is considered to be a single-phase homogeneous fluid, and its flow in a porous medium is modeled by using well-documented concepts of Newtonian and non-Newtonian fluid flow in porous media (26, 38). [Pg.251]

The distributed resistance models describe adequately the emulsion homogeneity resulting from the presence of the droplets of internal reagent dispersed in the emulsion globules. Two different approaches have been reported based on the nature of reaction with the internal reagent. [Pg.147]

Due to possibility to increase the quality of alkali and oil mixing via fine dispersion and uniform distribution of the alkali in the entire volume of oil, the conditions for the creation of a homogeneous emulsion-phase model of system liquid-liquid in tubular turbulent apparatus were studied [7, 8],... [Pg.143]

J. Floury, A. Desrumaux, and J. Lardieres Effect of High-Pressure Homogenization on Droplet Size Distributions and Rheological Properties of Model Oil-in-Water Emulsions. hmovat. Food Sci. Emergi. Technol. 1, 127 (2000). [Pg.42]

HUFT homogeneous nucleation model of emulsion polymerization I initiator... [Pg.3]

It should be noted that the preceding treatment of the emulsion phase/packet model is suitable for a system with homogeneous emulsion phase (i.e., particulate fluidization). The model needs to be modified when applied to the fluidized bed with a discrete bubble phase. [Pg.510]

The van der Waals interaction among the large particles of the system was calculated on the basis of a model that was previously employed to examine the stability of emulsions [16] and microemulsions [17]. In this model, a particular particle is considered to be surrounded by 12 nearest neighbor particles randomly located on a sphere of radius Ru and all the other particles of the system are assumed to be homogeneously distributed outside a sphere of radius R2 (Fig. 2). The radius Ri is selected as the average distance between large particles, and is therefore given by... [Pg.366]

Unzueta et al. [18] derived a kinetic model for the emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA) employing both the micellar and homogeneous nucleation mechanisms and introducing the radical absorption efficiency factor for micelles, F, and that for particles, Fp. They compared experimental results with model predictions, where they employed the values of Fp=10 and Fn,=10", respectively, as adjustable parameters. However, they did not explain the reason why the value of Fp, is an order of magnitude smaller than the value of Fp. Sayer et al. [19] proposed a kinetic model for continuous vinyl acetate (VAc) emulsion polymerization in a pulsed... [Pg.10]

As pointed out above, particle nucleation includes all three mechanisms -micellar, homogeneous, and droplet, since these mechanisms may compete and coexist in the same system. Often one will dominate. Therefore, any general model of emulsion polymerization should include all three mechanisms. Hansen and Ugelstad [31] and Song [10] have presented probabilities for each of these mechanisms in the presence of all three. [Pg.142]

In emulsion polymerization a single polymer particle can be regarded as a locus of bulk polymerization with intermittent initiation. A decrease in termination rate constant, which is observed in bulk polymerization, should, therefore, also occur in a single polymer particle and must be taken into account in model simulation of emulsion polymerization. However, since the polymer particles from the very beginning of the reaction contain a certain percentage of polymer, typically 20-40%, then the termination rate constant is always smaller in the beginning of emulsion polymerization than in the similar homogeneous bulk... [Pg.83]


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See also in sourсe #XX -- [ Pg.252 ]




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Emulsions models

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