Particle size distribution in emulsion polymerization

Industrial Engineering Chemistry Research 40, No.23,14th Nov. 2001, p.5177-83 NOVEL OPERATING METHOD FOR CONTROLLING LATEX PARTICLE SIZE DISTRIBUTION IN EMULSION POLYMERIZATION OF VINYLACETATE Ohmura N Kitamoto K Yano T Kataoka K Kobe,University... 

F. J. Doyle, C. A. Harrison, T. J. Crowley, Hybrid model based approach to batch-to-batch control of particle size distribution in emulsion polymerization . Computers Chem. Eng., 2003, 27, 1153. 

Feeney P.J., Napper D.H., Gilbert R.G. Coagulative nucleation and particle size distributions in emulsion polymerization. Macromolecules 1984 17 2520-2529 Feeney P.J., Gilbert R.G., Napper D.H.J. Periodic nucleation processes in emulsion polymerization systems. J. Colloid Interface Sci. 1985 107 159-173 Fomasiero D., GrieserF. Analysis of the visible absorption and SERS excitation spectra of silver sols. J. Chem. Phys. 1987 87(5) 3213-3217... 

Edouard D, Sheibat-Othman N, Hammouri H. Observer design for particle size distribution in emulsion polymerization. AICbE J 2005 5 3167-3185. 

Zeaiter J, Romagnoli JA, Gomes VG. Online control of molar mass and particle-size distributions in emulsion polymerization. AIChE J 2006 52 1770-1779. 

For example, the particle size distribution in emulsion, suspension, and precipitation polymerization can be a crucial product specification. One of the greatest difficulties in achieving quality control of the polymer product is that the actual customer specifications may be in terms of non-molecular parameters such as tensile strength, crack resistance, temperature stability, color or clarity, absorption capacity for plasticizer, etc. 

Immanuel, C. D., Cordeiro, C. F, Sundaram, S. S. et al. 2002 Modeling of particle size distribution in emulsion co-polymerization comparison with experimental data and parametric sensitivity studies. Computers and Chemical Engineering 26, 1133-1152. 

Lichti, G., R. G. Gilbert, and D. H. Napper, J. Polym. Sci. Polym. Chem. Ed., 18,1297 (1980) Theoretical Predictions of the Particle Size and Molecular Weight Distributions in Emulsion Polymerization, Chap. 3 in Emulsion Polymerization, I. Piirma, ed., Academic Press, New York, 1982. 

In 1952 W. J. Priest, in an important paper, laid out all of the basic qualitative features of the theory of homogeneous nucleation in emulsion polymerization as it is known today (12). This was based upon his studies of particle size distributions in vinyl acetate polymerization initiated by potassium persulfate (K2S20g) in the presence of varying amounts of different stabilizers and inhibitors at several temperatures. Priest proposed that (1) "polymerization in solution is the initial process" ... 

Poehlein and Degraff [336] extended the derivation of Gershberg and Long-field [330] to the calculation of both molecular weight and particle size distribution in the continuous emulsion polymerization of St in a CSTR. On the other hand, Nomura et al. [163] carried out the continuous emulsion polymerization of St in a cascade of two CSTRs and developed a novel model for the system by incorporating their batch model [ 14], which introduced the concept that the radical capture efficiency of a micelle relative to a polymer particle was much lower than that predicted by the diffusion entry model (pocd -°). The assumptions employed were almost the same as those of Smith and Ewart (Sect. 3.3), except that the model did not assume a constant value of p. The elementary reactions and their rate expressions employed in the first stage are as follows ... 

From mixed surfactant systems of emulsion polymerization, monodispersed latices were usually obtained at fairly low conversions with rather wide variations in emulsifier compositions (j ). Therefore, samples for the determination of the particle size distribution in this system should be taken at relatively low conversions, otherwise, monodispersed latices will be obtained due to competitive growth from all samples regardless of the surfactant ratios in the recipe of polymerization. These particles will be different in size, but not in size distribution. 

Theoretical Predictions of the Particle Size and Molecular Weight Distributions in Emulsion Polymerizations... 

Show-An, C. Kuo-Wei, W. Emulsion polymerization theory and particle size distribution in 32. copolymerization system. J. Polym. Sci. Pt. A ... 

Collins EA. Measurement of particle size and particle size distribution. In Lovell PA, El-Aasser MS, editors. Emulsion Polymerization and Emulsion Polymers. England John Wiley Sons 1997. p 385. 

THE PREDICTION OF PARTICLE SIZE AND MOLECULAR WEIGHT DISTRIBUTIONS IN EMULSION POLYMERIZATION... 

The batch emulsion polymerization is commonly used in the laboratory to study the reaction mechanisms, to develop new latex products and to obtain kinetic data for the process development and the reactor scale-up. Most of the commercial latex products are manufactured by semibatch or continuous reaction systems due to the very exothermic nature of the free radical polymerization and the rather limited heat transfer capacity in large-scale reactors. One major difference among the above reported polymerization processes is the residence time distribution of the growing particles within the reactor. The broadness of the residence time distribution in decreasing order is continuous>semibatch>batch. As a consequence, the broadness of the resultant particle size distribution in decreasing order is continuous>semibatch>batch, and the rate of polymerization generally follows the trend batch>semibatch>continuous. Furthermore, the versatile semibatch and continuous emulsion polymerization processes offer the operational flexibility to produce latex products with controlled polymer composition and particle morphology. This may have an important influence on the application properties of latex products [270]. 

Copolymers with butadiene, ie, those containing at least 60 wt % butadiene, are an important family of mbbers. In addition to synthetic mbber, these compositions have extensive uses as paper coatings, water-based paints, and carpet backing. Because of unfavorable reaction kinetics in a mass system, these copolymers are made in an emulsion polymerization system, which favors chain propagation but not termination (199). The result is economically acceptable rates with desirable chain lengths. Usually such processes are mn batchwise in order to achieve satisfactory particle size distribution. 

Many different combinations of surfactant and protective coUoid are used in emulsion polymerizations of vinyl acetate as stabilizers. The properties of the emulsion and the polymeric film depend to a large extent on the identity and quantity of the stabilizers. The choice of stabilizer affects the mean and distribution of particle size which affects the rheology and film formation. The stabilizer system also impacts the stabiUty of the emulsion to mechanical shear, temperature change, and compounding. Characteristics of the coalesced resin affected by the stabilizer include tack, smoothness, opacity, water resistance, and film strength (41,42). 

ABS compositions with bimodal particle size distributions of the grafted rubber can be prepared by emulsion graft polymerization techniques. The preparation of ABS types by emulsion polymerization consists in brief of (13) ... 

The emulsion free-radical polymerization carried out in different steps ensures a precise control of the particle size and particle size distribution. The particle diameter can be adjusted between 100 nm and 1000 nm, with a low polydispersity (generally less than 1.1) (Chapter 8). Rubber particles with sizes lower than 100 nm are ineffective for toughening purposes (Sec. 13.3.2b). 

This work has shown that by monitoring conversion curves by a computer, emulsifier metering can be varied to produce a desired particle size distribution of smalls in a seeded PVC emulsion polymerization. 

Synthesis. A series of latexes was prepared by semicontinuous emulsion polymerization of methyl methacrylate. A dialkyl ester of sodium sulfosuccinic acid surfactant yielded the narrow particle size distribution required. An ammonium persulfate/sodium metabisulfate/ferrous sulfate initiator system was used. The initiator was fed over the polymerization time, allowing better control of the polymerization rate. For the smaller size latexes (200 to 450 nm), a seed latex was prepared in situ by polymerizing 10% of the monomer in the presence of the ammonium persulfate. Particle size was adjusted by varying the level of surfactant during the heel reaction. As the exotherm of this reaction subsided, the monomer and the sodium metabisulfate/ferrous sulfate feeds were started and continued over approximately one hour. The... 

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