Polymerization continued latex particle size from

A number of studies endeavored to experimentally determine the values of the desorption rate constant. It is also interesting to note that Lee and Poehlein [46,48,49] modified the approach of Ugelstad et al. [8,9] and applied it to emulsion polymerization carried out in a single continuous stirred tank reactor (CSTR) system. The resultant latex particle size distribution data were then used to determine the value of A des. The k data obtained from other literature are summarized in Table 4.4. Significant variations in the values of k isi for the emulsion polymerizations of styrene at 60 °C are observed. 

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. 

With the concept of nanoreactors one can take advantage of an additional mode control for the design of nanoparticles where both thermodynamic aspects as well as shear history enter the particle size and the inner structure of the latexes or hybrid particles. The polymerization in such nanoreactors takes place in a highly parallel fashion, i.e., the synthesis is performed in 1018-102° nanocompartments per liter that are separated from each other by a continuous phase. In miniemulsion polymerization, the principle of small nanoreactors is realized as demonstrated in Fig. 1. 

A growth of the micellar size is always observed during the polymerization so that each final latex particle (d 30 run) is the result of the fusion of around 1(K) micelles. Nucleated particles grow by addition of monomer from other inactive micelles, either by coalescence with neighbouring micelles or by monomer diffusion through the continuous phase [48,53]. 

The latices that result from the emulsion polymerization find immediate application as adhesives, paints, coatings, or in the processing of leather. For this, control over the distribution of the latex particles is desired. If emulsifier and water are added at the beginning of the polymerization and monomer and initiator are added continually during the course of the polymerization, then only those latex particles initially formed will continue to grow. The latex particles are relatively small and show a narrow distribution of size. If, on the other hand, just one part of the initial sample is polymerized and the rest is added as an emulsion during polymerization, then new latex particles will be produced. Since the particles formed first are very large and those formed last remain relatively small, the distribution of sizes becomes very wide. 

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