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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 1412-1417 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 1618-1630 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of concentration on the sedimentation rate of uncharged rigid spheres was investigated. Three submicron sizes of silica spheres were prepared according to the method of Stöber (1968). The particles were sterically stabilized by chemisorption of stearyl alcohol at their surface by the method developed by van Helden (1981). The sterically stabilized silica particles dispersed in cyclohexane are known to behave as hard spheres. Monodisperse gravity sedimentation experiments were carried out for the various particle species over a wide concentration range of φ = 0.003 to φ = 0.37, where φ is the particle volume fraction in cyclohexane. The data for dilute suspensions (φ 〈 0.03) were found to be well described by Batchelor's equation: U/U0 = 1-6.55φ, where U is the sedimentation velocity and U0 is the Stokes velocity of a sphere in isolation. The data over the entire concentration range (0〈φ〈0.37) were found to be well described by the equation: U/U0 = (1-φ)6.55.Bidisperse sedimentation experiments were also carried out, and the dilute data were found to be well represented by Batchelor's 1982 theory for polydisperse suspensions. The high concentration data were analyzed in terms of a model that does not distinguish between interactions of like and unlike particles.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 3-16 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We investigated the effect of concentration on the Brownian diffusion of uncharged rigid spheres. Monosize silica spheres were prepared according to the method of Stöber (1968). The particles were sterically stabilized by chemisorption of stearic alcohol at their surface by the method developed by van Helden (1981).Particle radius was 14.5 nm from electron micrographs of the coated particles. Osmotic pressure measurements of the sterically stabilized particles dispersed in cyclohexane showed that the particles behaved as hard spheres. The measurements agreed well with predictions from the Carnahan-Starling equation over the concentration range 0.0458 〈 φ 〈 0.37 where φ is the volume fraction of the particles in the suspension. Viscosity measurements of silica dispersions were made over the concentration range 0 〈 φ 〈 0.25. The relative viscosity over the range 0 〈 φ 〈 0.2 was fitted by ηr = 1 + 2.4φ + 7.1φ2. The coefficients 2.4 and 7.1 in this equation are in good agreement with the theoretical values of 2.5 and 6.2 obtained by Einstein(1906) and Batchelor(1977), respectively. The Brownian diffusion coefficient of the particles dispersed in cyclohexane was measured over the concentration range 0.0055 〈 φ 〈 0.248 using Taylor's hydrodynamic stability method. A laser fiber-optic system was used to measure the transient concentration profile along the capillary as indicated by a fluorescent dye. This technique offers the advantage of being direct and nonintrusive. The experimental diffusivity data were found to be well described by the generalized Stokes-Einstein equation(Batchelor, 1976) over the entire concentration range studied.
    Additional Material: 12 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 57 (1995), S. 343-352 
    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: In this study, a novel series of water-soluble hydrophobically modified poly(vinyl alcohol) (PVA) is prepared by chemical modification of PVA, with the objective of investigating the polymer's rheological behavior for enhanced oil recovery applications. The solution viscosity of the polymer obtained is studied with respect to the polymer concentration, temperature, salinity, polymer modification, aging, shear rate, and polymer molecular weight. The solution viscosity of the PVA is greatly enhanced by the modification. The modified PVA exhibits a relatively high salt tolerance, typical of nonionic polymers, in the range of 0-7.0 wt % NaCl concentrations, and the viscosity of the polymer solution is relatively invariant with NaCl above 3.0 wt % NaCl concentration. Below 3 wt %, the viscosity shows a maximum then a minimum, an unusual behavior. Generally, the polymer exhibits an almost constant viscosity at high shear rates and a typical shear thinning behavior at low shear rates. In addition, increasing polymer concentration and molecular weight leads to an increase in the polymer solution viscosity. Moreover, the polymer exhibits smaller solution viscosity at a high temperatre, and a slight decrease in viscosity is also exhibited by the modified polymer with aging. Comparison of the viscosities of 18 polymer modifications indicates that the larger the numbers of hydrophobic groups (side chains) in the polymer structure, the smaller the viscosity. Moreover, the longer the hydrophobic groups (side chains) in the polymer structure, the greater the viscosity, if their number is small. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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