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  • 1
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Dielectric property ; permittivity ; electrical conductivity ; ion-exchanger ; interfacial polarization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01412044
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Dielectric property ; dielectric relaxation ; permittivity ; electrical conductivity ; ion-exchanger
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01410394
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Dielectricrelaxation ; distribution ; microcapsule ; permeability ; porassiumchloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00657304
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Dielectricproperty ; distribution ; microcapsule ; suspension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01410595
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