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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1461-1473 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mathematical model presented in Part I, accommodating the emulsion polymerization of vinyl acetate stabilized with poly(vinyl alcohol), predicts experimental conversion and particle size data with reasonable accuracy. Model predictions of measurable variables exhibit sensitivity to variables affecting either primary ungrafted particle nucleation of flocculation kinetics, but are relatively insensitive to variables affecting poly(vinyl alcohol) grafting reactions and the resulting primary grafted particle concentration. Semibatch simulations indicate that independent increases in the vinyl acetate, poly(vinyl alcohol), and initiator levels of all increase the primary grafted particle population. It is unlikely, however, that this population exceeds the ungrafted counterpart under most commercial polymerization conditions. This relative insignificance of grafting during particle nucleation is also noted in literature data simulations where, with appropriate parameter adjustments, the model predictions agree well with the batch, thermal initiation data. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 2157-2164 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The stability of vinyl acetate miniemulsions employing polyvinyl alcohol (PVOH) as the surfactant, and hexadecane and/or various polymers as the cosurfactant, were studied. Shelf lives (to phase separation) and monomer droplet sizes were measured. The results indicate that it is possible to prepare stable miniemulsions using a nonionic surfactant (PVOH) and hexadecane as the cosurfactant. Polymeric cosurfactants do not create stable miniemulsions but retard Ostwald ripening to an extent that allows predominant droplet nucleation. The polymerization behavior of these miniemulsion systems was investigated using on-line conductance measurements to differentiate droplet versus micellar/homogeneous nucleation. The effect of cosurfactant concentration on the reaction rate was compared for hexadecane and polymeric cosurfactants. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 633-655 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of the isothermal batch macroemulsion and miniemulsion polymerizations of methyl methacrylate (MMA) at 50°C have been studied. Hexadecane was used as the cosurfactant or swelling agent. The nucleation mechanisms were observed to be different between macroemulsions and miniemulsions. The effect of surfactant, cosurfactant, initiator, shear, and hold time on droplet nucleation was studied. The miniemulsion particles were found to contain more radicals on average than the macroemulsion particles using certain recipes. This resulted in higher polymerization rates for the miniemulsions at identical particle numbers. The latex-particle-size distributions were similar even though the mini-emulsion droplets start out with a high polydispersity of around 1.5. Miniemulsion latexes were found to be more stable under shear. Conductance of emulsions during polymerization was found to be a valuable on-line tool for investigating particle nucleation and growth. © 1993 John Wiley & Sons, Inc.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 1833-1841 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The addition of a monomer soluble polymer to an emulsion was found to slow the effects of Ostwald ripening and impart diffusional stability to the droplets. Droplet nucleation was found to be the dominant nucleation mechanism in the polymerization of these polymer-stabilized miniemulsions (as distinguished from true miniemulsions). As a result these nucleations were more robust, and the polymerizations were less sensitive to variations in the recipe or contaminants levels. This was evident in the rates of polymerization and in the particle numbers. The miniemulsion polymerizations were subjected to changes in initiator concentration, a water-phase retarder, an oil-phase inhibitor, and agitation. Particle number was found to vary with each of these factors to the powers of 0.002, 0.02, 0.0031, and -0.026, respectively. The corresponding exponents for conventional emulsion were one to two orders of magnitude greater. These results demonstrate the potential of miniemulsion polymerization to greatly reduce the variability in particle number found in conventional emulsion polymerizations. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 2069-2076 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Emulsion and miniemulsion copolymerizations were carried out with acrylic monomers (methyl methacrylate, butyl acrylate, and acrylic acid) in the presence of an alkyd resin. Poly(methyl methacrylate) was used as a hydrophobe or cosurfactant in the miniemulsion reactions. The results demonstrate that miniemulsion polymerization is the preferred process, probably because of mass transport limitations of the alkyd in the conventional emulsion polymerization reactions. The monomer emulsions prepared for the miniemulsion reactions were much more stable and the polymerizations were free of coagulum. Reaction rates, particle size characteristics, grafting efficiencies, and some film properties were measured. © 1996 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 407-430 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Three process sensors are discussed, one for the determination of surface tension and two for the determination of liquid density. All three methods are on-line, compatible with digital data acquisition systems, and capable of monitoring flowing process streams. The instruments are described and calibration data are given. Two mathematical models of the bubble tensiometer are developed. Data showing the application of these instruments to the monitoring of batch and continuous emulsion polymerization are given.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 1449-1460 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mathematical model for particle nucleation and growth in the isothermal semibatch emulsion polymerization of vinyl acetate stabilized with poly(vinyl alcohol) is presented. In addition to the particle nucleation and growth mechanisms governing ionically stabilized polymerizations of relatively water-soluble monomers, the model accommodates grafting onto the poly(vinyl alcohol) backbone during nucleation, and polymeric stabilization. The user supplies the emulsion recipe, process conditions and kinetic parameters, and the model predicts the various species concentrations, along with the conversion and particle size and number profiles. In part II, model predictions are discussed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 60 (1996), S. 251-262 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Emulsions stabilized against diffusional degradation by incorporating a polymeric cosurfactant have been produced and polymerized. The presence of large numbers of small droplets shifts the nucleation mechanism from micellar or homogeneous nucleation, to droplet nucleation. When an efficient cosurfactant is used, this process is referred to as miniemulsion polymerization. Polymer, however, is known to be a poor cosurfactant. Its advantage is that, unlike most cosurfactants, it is innocuous in the recipe. Results indicate that even a poor cosurfactant (polymer) is adequate to stabilize small droplets against diffusional degradation long enough to nucleate them into polymer particles. The dependence of the concentration and molecular weight of the cosurfactant on the droplet size and distribution is investigated. Droplet diameters range from 19.5 to 141.2 nm with polydispersities of about 1.023. The polymeric cosurfactant is found to affect the mechanism of nucleation. On-line conductance measurements are used to successfully differentiate between nucleation mechanisms. The observed reaction rates are dependent on the amount of polymeric cosurfactant present. In addition, the latexes prepared with the polymeric cosurfactant have lower polydispersities (1.006) than either latexes prepared from classical emulsions (1.049) or from alkane-stabilized miniemulsions (1.037). © 1996 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 1259-1276 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Experimental data on the dynamics of the continuous emulsion polymerization of methylmethacrylate are presented. Techniques for on-line reaction monitoring and digital data acquisition as reported previously are used to generate dynamic data on the monomer conversion and free emulsifier concentration. Data are reported confirming the existence of multiple steady states and limit cycles in the CSTR (continuous stirred tank reactor) emulsion polymerization of methylmethacrylate. Data are also reported suggesting the presence of steady states in the absence of micelles in the reactor. The possible causes of these phenomena, and the conditions under which they occur are discussed.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 350-354 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chawla, et al. (2) recently described a new SISO control algorithm called the Conservative Model Based Control (CMBC). In this paper, we assess the feasibility of implementing CMBC as a multiloop controller on a simulated reactor used for the polymerization of methyl methacrylate. Both servo and regulatory behavior of the controller are studied. Despite the non-linearities and coupling between the two controlled variables, the easy-to-implement CMBC algorithm has been shown to give good control performance.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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