Dielectric and thermoanalytic behavior of moisture and water in aromatic polyamide paper

Specimens of an aromatic polyamide (Aramid) paper, which were subjected to various degrees of moisture adsorption as well as water immersion, were investigated in order to estimate how much the adsorbed moisture and the stored water affect the dielectric and thermoanalytical behavior. In the humid specimens the dielectric properties did not change much and there were no endothermic and exothermic peaks. In the soaked specimens the dielectric properties changed remarkably and there were endothermic and exothermic peaks due to free water recognized at ~0°C. It is concluded that the dielectric properties of Aramid paper are rather stable to moisture adsorption because its polyamide linkage bonds tightly with the adsorbed water which is in the shape of nonfreezing bound water, but when the total water content increases over the saturated moisture value of 6.8%wt, increases in the dielectric properties take place due to the free water in the fiber structure. In the bound water region, Aramid paper has higher DC resistivity values compared with other synthetic papers such as polyester paper