T. Skodvin et J. Sjoblom, DIELECTRIC-SPECTROSCOPY ON W O EMULSIONS UNDER INFLUENCE OF SHEAR FORCES/, Colloid and polymer science, 274(8), 1996, pp. 754-762
The dielectric properties of concentrated w/o-emulsions have been inve
stigated, both at rest and during shear. The volume fraction water ran
ged from 0.50 to 0.95. The time domain dielectric spectroscopy techniq
ues (TDS) was used to record the dielectric spectra, which covered the
frequency region from 25 MHz to 2 GHz. In order to simultaneously rec
ord rheological and dielectric data a modified viscometer of the coaxi
al cylinder type was applied. A close connection between the viscosity
and the dielectric properties of w/o emulsions is demonstrated. The v
ery large effects of shear both on the static permittivity and the die
lectric relaxation time for the emulsion can partially be ascribed to
the degree of flocculation in the system. At high shear rates, at whic
h the emulsions are expected to have a low degree of flocculation, the
observed dielectric properties differ from those expected from a theo
retical model for spherical emulsion droplets.