The Electrical Behavior of an Insulating Liquid Layer between Polymer Sheets Under AC Voltage

The diffuse part ofthe electric double layer spontaneously present at an insulator/liquid interface can be displaced by an ac field. It is shown that the diffuse part of the double layer acts as a reservoir of ions which gives rise to a time-limited unipolar injection. At low fields, the ta. ngent of the loss angle tan¿ increases when the voltage V is increased. At high fields, the reservoir of charges depletes quickly and the charges swept away by the field are stopped by the opposite wall. Here tan¿ decreases in a way similar to the Garton effect, although the physical model is completely different. Experimental results are in agreement with the theoretical predictions. The influence of liquid conductivity, space charge, type of ions, and electrohydrodynamic liquid motion is discussed.