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.
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Abbreviations
- ɛ :
-
relative permittivity
- ϰ:
-
electric conductivity
- ε * :
-
complex relative permittivity:ɛ *=ɛ−j(ϰ/2πfε v)
- ∃ v :
-
permittivity of vacuum
- Φ :
-
volume fraction of the disperse phase
- f :
-
measuring frequency
- fo :
-
relaxation frequency corresponding to a halfvalue point of the entire dielectric relaxation
- a :
-
continuous medium
- i :
-
disperse phase
- h :
-
limiting value at high frequencies
- l :
-
limiting values at low frequencies
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Hanai, T., Imakita, T. & Koizumi, N. Analysis of dielectric relaxations of w/o emulsions in the light of theories of interfacial polarization. Colloid & Polymer Sci 260, 1029–1034 (1982). https://doi.org/10.1007/BF01451650
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DOI: https://doi.org/10.1007/BF01451650