Effect of molecular hindrance on dc conductivity in dielectric liquids including water

Abstract

1.IntroductionThe moisture or humidity has significant effect on the electrical properties of dielectric liquids. In order to discuss the mechanisms of the effects, we have been investigated the state of water in many kinds of dielectric liquids,The details of the water state can be analyzed from IR spectrum of water molecules, because the fonnation of the water cluster by hydrogen bonding makes the molecular vibrations to be lower frequency. In our previous studies, the following results have been obtained [ 11 [2] [ 31. 1 :The state of water in saturated hydrocarbons, for example liquid paraffin, is "free water"(it is as saine as water vapor), because there is no polarization site where the water molecules combine. 2:Tlie state of water in unsaturated and aromatic hydrocarbons is "binded water", which combine the polarization base of the liquids. 3:Tlie effect of biiided water 011 conductivity(dc) is quite bigger than free water. 4:The hydrogen bonding energy of the biiided water. that can be calculated from IR spectrum, and the stronger the hydrogen bonding energy. the higher the conductivity as if the amount of water in the liquid is as same as each other.The above results indicate that the water effect on conductivity caused by not only the amount of water but also the formation of water cluster. Our model of effect of such water cluster on conductivity is that the water cluster fonns the conduction bridge in dielectr IC liquids In this paper, we control the molecular hindrance in order to control the length of side chain of dielectric liquids in order to change the effect of water cluster on conductivity 2.Experimental MethodThe samples used was acetic acid groups that are methyl, ethyl, butyl, pentyl, hexyl and dodecyl acetate.The dc conductivity was measured by using the parallel to parallel electrodes. 'The gap length was 0.5innir and the area was 2.0~111~. Because the electrodes was made by thc glass plate with conduction surface, this electrodes system was able to path through IR beam. Therefore the IR spectixiin of water cluster in samples was able to be measured under the electrical field. The coilduction current was measured by nano ampere meter, and the conductivity was calculated from the current which was measured IO minutes later after the voltage applied. Fig. 1 shows the saniples of the infrared spectra of water in order to explain the hydrogen bonding energy. In this figure. the spectra of water have two broad peaks in dimer region. The peak in higher wave number indicate IJ bond and peak of lower wave number indicate 11 bond. The hydrogen bonding energy of water is calculated by the quantity of peak shift from the basic band of water ( IJ =3657cni-' v ;=3756ciii-') to the