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  • 1
    Electronic Resource
    Electronic Resource
    Dielectric properties of quaternary ammonium ion-exchange beads dispersed in aqueous phases (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 477-480 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; permittivity ; electrical conductivity ; ion-exchanger ; interfacial polarization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric measurements were carried out for dense sediments of quaternary ammonium type anion-exchange resin beads dispersed in deionized water over a frequency range of 30 Hz to 130 MHz. According to a method proposed in previous studies the relative permittivities and electrical conductivities of ion-exchange beads were evaluated from the relaxation data observed in a megahertz region on the basis of a theory of interfacial polarization. The permittivities of the ion-exchange beads were found to be unchanged irrespectively of the salt form and somewhat lower than that of a continuous medium, while the conductivities of the ion-exchange beads were characteristic of the salt form. The equivalent ionic conductances of different counter anions in the beads were estimated from the conductivities of the ion-exchange beads. These results indicate an ion-binding effect in the resin beads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412044
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric properties of ion-exchange beads of sulfonic acid type dispersed in aqueous solutions — effect of fixed charge density (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 428-432 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric property ; dielectric relaxation ; permittivity ; electrical conductivity ; ion-exchanger
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Ion-exchange beads with different densities of fixed charges were prepared by sulfoethylation of dextran gel beads. The relative permittivities and the electrical conductivities of the ion-exchange beads in a sodium form were evaluated by a dielectric technique consisting of the following two procedures proposed in a previous study (2): (a) Dielectric measurements for densely packed sediments of the ion-exchange beads; (b) Analysis of the observed dielectric relaxations by means of a theoretical equation of interfacial polarization for suspensions of spherical particles. The deduced permittivities of the ionexchange beads in equilibrium with water were about 60, which is lower than those of outer aqueous phases. The deduced conductirities were of the order of 1 to 10 mS cm−1 and were increased reasonably with the fixed charge density. Closer consideration on these deduced values indicates that no specific interaction exists between the counter ions and the fixed charges irrespective of changes in fixed charge density and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410394
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of dielectric relaxations due to the interfacial polarization for two-component suspensions of spheres (1986)
    Springer
    Colloid & polymer science 264 (1986), S. 888-895 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric relaxation ; dielectric theory ; interfacial polarization ; relative permittivity ; suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A theoretical formula of dielectric relaxation in a form of complex relative permittivity is derived for dilute suspensions of spherical particles of two kinds on the basis of the Maxwell-Wagner theory of interfacial polarization. Another theoretical formula is derived further for concentrated suspensions of spheres of two kinds on condition that the formula derived above holds for the infinitesimally increasing process in concentration of the dispersed spheres. Furthermore a theoretical formula is derived for concentrated suspensions of shelled spheres of two kinds as the extension of the formula for concentrated suspensions. By use of the theoretical formulas proposed, values of the permittivities and the conductivities of the two-component suspensions were calculated for some examples with different sets of phase parameters. Results of the numerical calculation demonstrates dielectric relaxation profiles full of variety and characteristic of the suspensions containing two kinds of spheres covered with or without shells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410640
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric analysis of PMMA microcapsules containing an aqueous KCl solution to derive a distribution function of the release rate of KCl (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 880-888 
    Details
    ISSN: 1435-1536
    Keywords: Dielectricrelaxation ; distribution ; microcapsule ; permeability ; porassiumchloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Release of KCl from a batch of PMMA microcapsules containing an aqueous 3 mM KCl solution was studied with the following two methods: 1) dielectric measurements of suspensions of the microcapsules in distilled water. The electrical conductivity of capsule interior was estimated with this method. 2) Measurements of the conductivity of suspending medium of the microcapsule suspensions. These two kinds of experiments provided us with information about the amount of KCl remaining in the capsules and that diffused outside. Results of these experiments showed that the microcapsules varied in their release rate of KCl. A distribution function of the release rates was derived from the results of the dielectric measurements. That distribution function was successful in explaining the results of the measurements of the conductivity of suspending medium. Furrther examination revealed that the release rate increased with the increase in the thickness of capsule wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657304
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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical study of dielectric behavior of microcapsule suspensions with distributed drug release rate (1990)
    Springer
    Colloid & polymer science 268 (1990), S. 1059-1065 
    Details
    ISSN: 1435-1536
    Keywords: Dielectricproperty ; distribution ; microcapsule ; suspension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Theoretical consideration is made concerning the dielectric behavior of aqueous suspensions of W/O-type microcapsules containing aqueous electrolyte solutions, especially concerning distribution effects of the electrolyte release rate on the dielectric behavior. It is shown at first that the distribution of the release rate causes electrical conductivity of the capsule interior. Next, it is deduced, in the light of a theory of the interfacial polarization, that the distribution characteristics of the capsule interior's electrical conductivity are closely related to those of the relaxation time for a dielectric relaxation exhibited by the suspensions. Several formulas are derived to describe the relation between the distribution characteristics of the release rate and those of the relaxation time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410595
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Dielectric observations on polystyrene microcapsules and the theoretical analysis with reference to interfacial polarization (1983)
    Springer
    Colloid & polymer science 261 (1983), S. 381-389 
    Details
    ISSN: 1435-1536
    Keywords: Conductivity ; Dielectric property ; Dielectric relaxation ; Interfacial polarization ; Microcapsule ; Permittivity ; Polystyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dielectric measurements were carried out for polystyrene microcapsules which were prepared by means of an interfacial polymer deposition technique. The microcapsules showed a couple of dielectric relaxations termedP for lower andQ for higher frequencies. The frequency profiles were characteristic of the structure that shelled spheres were dispersed in a continuous medium. Gelatin aqueous solutions, cationic polyelectrolyte solutions and distilled water were loaded in the capsule interior to examine the effect of conductivities of the constituent aqueous phases on the dielectric properties. Relaxation frequencies of the relaxationsP andQ observed were directly proportional to the conductivities of the continuous medium and of the capsule interior, respectively. A dielectric theory was proposed for a suspension of shelled spheres in a continuous phase in order to analyze the relaxation data observed for the microcapsules. Volume fraction of the capsules, relative permittivity and conductivity of the capsule interior and thickness of the capsule wall are evaluated from the dielectric observations by use of the theoretical formulas derived. The dielectric behavior observed for the polystyrene microcapsules are interpreted quantitatively in terms of the dielectric theory proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418210
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of dielectric relaxations of w/o emulsions in the light of theories of interfacial polarization (1982)
    Springer
    Colloid & polymer science 260 (1982), S. 1029-1034 
    Details
    ISSN: 1435-1536
    Keywords: Dielectric relaxation ; W/O emulsions ; Interfacial polarization ; Permittivity ; Emulsifier ; Electric conductivity ; Disperse system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An attempt is made to apply dielectric theories of interfacial polarization to observations of dielectric relaxations for W/O emulsions. Approximate formulas for disperse systems in a W/O type were derived from the two theories: one proposed by Maxwell and Wagner for dilute disperse systems of spherical particles, and the other developed by Hanai for concentrated disperse systems. Dielectric measurements were carried out on concentrated W/O emulsions prepared from kerosene and distilled water or KCl aqueous solutions by minimal use of emulsifiers. Marked dielectric relaxations were observed with the emulsions, the dielectric parameters having been determined to characterize the relaxation data. Phase parameters such as relative permittivity, electric conductivity and volume fraction of the disperse phase were evaluated from the dielectric parameters by use of the approximate formulas of the respective theories. The phase parameters evaluated and the frequency dependence of complex permittivity of the W/O emulsions deduced from the theory for concentrated disperse systems are in excellent agreement with the observed data in comparison to that for dilute disperse systems. It is concluded that the dielectric relaxations due to the interfacial polarization of disperse systems of spheres are explained satisfactorily by the theory for concentrated disperse systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01451650
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