Role of micellar equilibria on modelling of batch emulsion polymerization reactors

Morbidelli, Massimo; Storti, Giuseppe; Carrà, Sergio

doi:10.1002/app.1983.070280302

Cited by 26 publications

(15 citation statements)

References 36 publications

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“…Moreover, the obtained model parameters present small errors (Table V), with the exception of K eq in R2 and R4. As shown by Immanuel et al,26 Morbidelli et al,27 and Saldivar et al,28 this is not unusual and should not be overemphasized.…”

Section: Conductivity Measurements During Emulsion Polymerizationsmentioning

confidence: 71%

Online monitoring of the evolution of the number of particles in emulsion polymerization by conductivity measurements. I. Model formulation

Santos

Lima

Pinto

et al. 2003

J of Applied Polymer Sci

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ABSTRACT:A conductivity meter is an inexpensive instrument that can easily be installed in polymerization reactors. This instrument can be used to monitor ionic species without time-consuming calibrations. A probe is inserted into the media, providing in situ measurements of conductivity in real time. For emulsion polymerization reactions, the conductivity meter can respond to changes in the ionic surfactant concentration, allowing the determination of surfactant dynamics in the media. The surfactant concentration can then be related to the changes in the surface area of the polymer particle phase, which can be linked to nucleation or coagulation phenomena. In this study, a conductivity meter was coupled to a calorimetric reactor to provide in situ and online measurements of conductivity during the emulsion polymerization of styrene, with sodium dodecyl sulfate as an anionic surfactant and with potassium persulfate as a free-radical initiator. A semiempirical model was built to describe the conductivity signal as a function of the latex composition and the reactor temperature. The model was inverted and combined with the available conductivity signal, conversion, and temperature measurements and was able to accurately predict the number of polymer particles in the latex and the surfactant concentrations in the many phases, without online measurements of the particle size.

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Section: Conductivity Measurements During Emulsion Polymerizationsmentioning

confidence: 71%

Online monitoring of the evolution of the number of particles in emulsion polymerization by conductivity measurements. I. Model formulation

Santos

Lima

Pinto

et al. 2003

J of Applied Polymer Sci

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“…In contrast to emulsion polymerization, where scores of models have been forwarded [5][6][7][8][9][10][11][12][13][14][15] , only three papers dealing with the modeling of microemulsion polymerization have been reported [16][17][18] . Guo et al developed a model for the thermally initiated polymerization of styrene in four-component microemulsions (styrene, water, surfactant and alcohol) 16) .…”

Section: Introductionmentioning

confidence: 99%

On the modeling of microemulsion polymerization. Experimental validation

Mendizábal

Flores

Puig³

et al. 2000

Macromol. Chem. Phys.

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A recently developed model for o/w microemulsion polymerization, tested only with styrene, is validated here by comparing its predictions with experimental data from the polymerization of three monomers with different chemical structures and water solubilities. The model reproduces well the kinetic data as well as the characteristics of the latex and polymer (particle size, average molar mass, number of polymer chains per particle, etc.) for the three monomers. The model predicts only two reaction rate intervals and that the conversion at which the maximum reaction rate occurs, depends only on the type of monomer and reaction conditions, in agreement with experimentally reported data. In the model, both micellar and homogeneous nucleation mechanisms are permitted, even for low water‐solubility monomers such as styrene, because of the large amounts of surfactant typically employed in microemulsion polymerization. The role of these two mechanisms in the polymerization process is examined here.

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“…The simulation of emulsion polymerization of styrene is the subject of many publications, in which the authors discuss the dependence of the kinetics of the process on the emulsifier and initiator concentration [130], the particle size distribution [127,[131][132][133][134], and the molecular mass distribution [135][136][137][138][139] and perform a complete simulation of the kinetic characteristics of the process [24,38,130,[140][141][142][143][144][145]. However, all these studies are based on the Harkins-Yurzhenko qualitative theory and disregard the participation of microdroplets in the formation of PMPs.…”

Section: Model Of Styrene Emulsion Polymerization the Effect Of The mentioning

confidence: 99%

An Advanced Approach on the Study of Emulsion Polymerization: Effect of the Initial Dispersion State of the System on the Reaction Mechanism, Polymerization Rate, and Size Distribution of Polymer-Monomer Particles

Khaddazh¹,

Литвиненко²

2012

Polymerization

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According to these ideas, in the presence of surfactants, the initial emulsion consists of two kinds of particles of different sizes: the monomer droplets with diameters of 5-20 microns and colloidal degree of dispersion and monomer-swollen surfactant micelles (5-10 nm).The mechanism of Harkins-Yurzhenko lied in the base of Smith and Ewart quantitative theory [5][6][7], with further refinements in the works of other authors . The main aspect of this theory is that radicals formed in the aqueous phase are trapped by the monomer swollen surfactant micelles and turn to PMP. It is assumed that only one out of every 100-1000 micelles captures a radical and becomes PMP, and the rest of the micelles are spent to stabilize the growing PMPs. Polymer-monomer particles formation ends with the disappearance of micelles of the emulsifier in the aqueous phase, after which the number of particles remains constant.Initial system contains monomer droplets with a diameter of 5-15 microns, their concentration being 10 12 -10 14 droplets/l, the monomer-swollen micelles with diameters of 5-10 nm and the number of micelles 10 18 -10 21 l -1 , and a water-soluble initiator (usually potassium persulfate) at a concentration of 1% per monomer [8]. Only a small fraction of the molecules of the monomer is located in the interior of the micelles (1-2%) and is dissolved in the aqueous phase (0.03% for styrene). In the aqueous phase, 10 14 -10 16 PMP / l are formed with a diameter in the range of 20-200 nm. Monomer droplets due to their relatively small surface area hardly compete with micelles in capturing radicals.In the polymerization process PMPs increase their size due to the diffusion of the monomer from droplets and monomer-swollen micelles which contains no radicals [1-3, 5, 9-15].Three limiting cases were considered:1. The number of free radicals in the particles is small compared with the total number of radicals, thus the average number of radicals per particle is much less that unity. 2. The average number of radicals per particle is equal to 0.5. This case is realized under following conditions: the activity of the radical in the particle persists as long as the second radical enter the particle, and the time of chain-breaking is small as compared with the average time interval of successive absorption of radicals by the particle. The authors believe that case 2 corresponds to the emulsion polymerization of styrene in the presence of potassium persulfate [5]. The rate of formation of primary radicals is equal to 10 13 radicals• ml -1 s -1 . The average number of polymer particles is of the order of 10 14 -10 16 in 1 ml of the system. If all the radicals formed by the decay of the initiator enter the polymer particles, the average frequency at which a radical enters a particle is once per 10 -100 sec. At any time, the particle contains either one radical or does not contain radicals at all, since it is assumed that chain termination occurs immediately in contact with the second radical in the particle. The particle is inactive unt...

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Role of micellar equilibria on modelling of batch emulsion polymerization reactors

Cited by 26 publications

References 36 publications

Online monitoring of the evolution of the number of particles in emulsion polymerization by conductivity measurements. I. Model formulation

Online monitoring of the evolution of the number of particles in emulsion polymerization by conductivity measurements. I. Model formulation

On the modeling of microemulsion polymerization. Experimental validation

An Advanced Approach on the Study of Emulsion Polymerization: Effect of the Initial Dispersion State of the System on the Reaction Mechanism, Polymerization Rate, and Size Distribution of Polymer-Monomer Particles

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