Models for the Dielectric Properties of Flocculated W/O-Emulsions

✍ Scribed by Tore Skodvin; Johan Sjöblom

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 654 KB
• Volume: 182
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1996.0450

✦ Synopsis

the state of the system (Fig. 1). These processes also influ-Theories on the dielectric properties of heterogeneous mixtures ence the dielectric properties (8)(9)(10)(11)(12). Thus the dielectric are commonly applied to predict or explain the dielectric properproperties of one given sample may considerably vary over ties of emulsions. However, the theories require ideal systems with a period of time ( 12), depending on the emulsion state. a homogeneous distribution of the dispersed particles. In emul-The effect of flocculation on the dielectric properties of sions this requirement is rarely fulfilled since flocculation and sedidisperse systems is well documented, when it comes to both mentation continuously will lead to an uneven distribution of the suspensions of solid particles or emulsions. Genz et al. (9)

droplets throughout the volume of the system. In this work we found that the conductive and dielectric properties of suspensuggest different models for prediction of the dielectric properties sions of carbon black in mineral oil were highly dependent for flocculated emulsions. These models are based on the traditional theories, but the structure and volume of flocculated aggre-on shear. When a shearing force was applied on the suspengates are also taken into account. Numerical calculations on these sions flocculated, aggregates were torn apart and a reduction models give higher static permittivities than what would be prein the permittivity levels was observed. When the shearing dicted from a model presupposing only unflocculated droplets. stopped, the permittivity rose to previous levels. Thus the Earlier it has been shown experimentally that flocculation leads reversibility of the shear-induced floc disintegration could to an increase in the permittivity levels.