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  • 1
    Digitale Medien
    Digitale Medien
    Growth of poly(methyl methacrylate) particles in three-component cationic microemulsions (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1161-1168 
    Details
    ISSN: 0887-624X
    Schlagwort(e): microemulsion ; polymerization ; methyl methacrylate ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Polymerization of methyl methacrylate (MMA) has been studied in ternary microemulsions which were stabilized by tetradecyltrimethylammonium bromide (TTAB) or stearyltrimethylammonium chloride (STAC). The sizes of MMA-swollen polymer particles (Rh) increased continuously during polymerization. This is in contrast to that of the styrene system, where Rh increased very rapidly to a maximum and then decreased continuously towards a constant value. The continuous growth of PMMA particles at 60°C are discussed. The stability of PMMA latexes increased with increasing the hydrophobic chain length of the cationic surfactant used. Traces of the coagulations of PMMA particles in the TTAB system can be seen from TEM. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pola.1995.080330719
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  • 2
    Digitale Medien
    Digitale Medien
    Hydrodynamic characteristics of dual Rushton impeller stirred vessels (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 332-346 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The flows generated in vessels stirred by two Rushton impellers were investigated in two vessels of diameter (T) 100 and 294 mm with impellers of diameter D = T/3 using flow visualization, power consumption, mixing time, and 360° ensemble-averaged and 1° angle-resolved LDA measurement techniques. The flows depended strongly on the clearance of the lower impeller above the base of the vessel (C1), the separation between the impellers (C2), and the submergence (C3) of the upper impeller below the top of the liquid column height (H). When these distances were varied, three stable and four unstable flow patterns were observed. Comparisons between the two LDA techniques showed that while the 360° ensemble-averaged measurements are useful for characterizing the overall flow structure and turbulence levels in the vessel, care must be exercised when interpreting such data, since in the impeller region they include periodic variations in the mean velocity in addition to the turbulent fluctuations. The trailing vortex structure and flow periodicity produced by the Rushton impellers is shown to decay significantly within a cylindrical region of height 1.2D and radius 1.0D centered around the middle of the vessel, when C1 = C2 = T/3. The turbulence structure within this region is anisotropic, while outside this region it might be considered mostly isotropic. The main flow features scaled well between the vessels.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690420204
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  • 3
    Digitale Medien
    Digitale Medien
    Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. II. Physical and mechanical properties of copolymer latex films (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 2221-2234 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Vinylidene chloride (VDC)-butyl methacrylate (BMA) copolymer latex films of various compositions (83 : 17, 60 : 40, 33 : 67 in mol %), prepared by batch and semicontinuous processes, were investigated for their physical properties by infrared spectroscopy, 13C solidstate NMR spectroscopy, X-ray diffraction, solubility in various solvents, differential scanning calorimetry (DSC), and water vapor transmission rates (WVTR), and for their mechanical properties by dynamic mechanical spectroscopy (DMS), and tensile strength measurements. Semicontinuous latex films were found to be homogeneous in composition and amorphous in character. On the other hand, batch latex films containing high VDC monomer content were heterogeneous in composition and crystalline in character. These differences were found to reflect the effect of mode of monomer addition during the emulsion polymerization process, and correlated well to the results on kinetics, colloidal, and surface properties of the VDC-BMA copolymer latexes, as described in the first part of this study.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1992.070451218
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  • 4
    Digitale Medien
    Digitale Medien
    Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. I. Kinetics in VDC-BMA emulsion polymerization and surface and colloidal properties of VDC-BMA latexes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 2207-2219 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Vinylidene chloride (VDC) - butyl methacrylate (BMA) comonomer mixtures with various composition (83 : 17, 60 : 40, 33 : 67 in mol %) were polymerized at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization. The reactivity ratios determined in VDC (M1) - BMA (M2) emulsion copolymerization system were r1 = 0.22 and r2 = 2.41. Seven 35% solids (83 : 17 mol %) VDC-BMA copolymer latexes were prepared: one batch (G), one seeded batch (F), and 5 seeded semicontinuous polymerizations of 5 different monomer feed rates ranging from 0.27 (A) to 1.10 wt %/min (E). The kinetic studies of seeded semicontinuous polymerizations A-E showed that the rates of polymerizations (Rp) were controlled by the monomer addition rates (Ra). The conversion versus time curves for the polymerizations of 0 : 100-100 : 0 VDC-BMA mixtures by batch polymerization showed that the rate of polymerization (Rp) was a function of the number of particles, and that the rate of polymerization in a latex particle (Rpp) increased with increasing proportions of butyl methacrylate in the monomer mixture. All of the latexes had narrow particle size distributions. The greater particle number density in VDC polymerization and the greater water solubility of VDC suggest that the homogeneous nucleation mechanism is operative in VDC-BMA copolymerizations. The latex copolymers prepared by semicontinuous polymerization had lower number-and weight-average molecular weights than those of the corresponding batch copolymers, resulting from the monomer starvation occurring during the semicontinuous polymerization. The surface characterization study of the cleaned latexes showed that for the latexes by batch process, the surface charge density derived from strong-acid groups decreased with increasing proportion of VDC in the monomer mixture. On the other hand, for the latexes prepared by semicontinuous polymerization, the surface charge density derived from strong-acid groups did not depend on the monomer composition of the copolymers.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1992.070451217
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  • 5
    Digitale Medien
    Digitale Medien
    Velocity characteristics of steady flow through a straight generic inlet port (1995)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 571-590 
    Details
    ISSN: 0271-2091
    Schlagwort(e): CDF ; predictions ; laser Doppler anemometry ; inlet port ; cylinder ; turbulence ; steady flow ; Engineering ; Engineering General
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: This paper presents a combined experimental and computational study of the steady flow through an internal combustion engine inlet port. The port was of generic design with a straight centreline. The three-dimensional velocity and turbulence fields in the port and cylinder were simulated using a computational fluid dynamics programme. Laser sheet flow visualization and laser Doppler anemometry were also employed to investigate the flows and assess the predictions. The results show that a large-scale flow structure is created in the cylinder by the inlet jet and its interaction with the valve and cylinder walls. Both predictions and measurements show that the flow is strongly dependent on the valve lift but is not affected by the flow rate. Comparisons of the numerical predictions with the experimental data indicated that the mean flow features are accurately predicted in many parts of the flow field; some discrepancies are evident and stem primarily from the failure of the simulation to predict a small recirculation region in the port which affects the trajectory of the annular jet entering the cylinder. Calculations were also made without modelling the port shape by using simplified inlet conditions upstream of the valve seat. It was found that this approximation can provide a reasonable, albeit less accurate, description of the flow, but modelling of the port shape is necessary for accurate flow predictions.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/fld.1650210704
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