Investigation of surface potential discharge mechanism and kinetics in dielectrics exposed to different organic solvents

Abstract

Dielectrics are extensively applied in several fields due to their strong charge retention properties. Filters, for respirator and ventilation applications, are commonly made of dielectric materials due to the increased charge retention which enhances their efficiencies. However, when they are exposed to organic solvents their charge retention drops significantly causing charge degradation. Several mechanisms were hypothesized to trigger this phenomenon. In this study, we investigated the discharge of dielectric filters composed of polymers, focusing on several hypotheses including the surface charge neutralization caused by ions assumed to be present during organic solvent evaporation, the ability of the organic solvent molecules to act as ion scavengers and the charge de-trapping due to the swelling of the polymer filter exposed to different organic vapors. It was observed, experimentally, that there were no measureable ions in the vapors of the organic solvents and that the organic molecules could not act as ion scavengers. An in-situ discharging and monitoring setup enabled us for the first time to study the degradation kinetics of the surface potential of polymer dielectric filters, which generally included three phases for the majority of the investigated polymer filter samples. The surface potential was steady for a certain period then it decreased following a profile close to an exponential function, and finally it approached zero volt. It was assumed that a critical swelling degree should be reached to initialize the charge de-trap. Overall, solubility of the polymer filter in different solvents, organic vapor diffusion coefficient and equilibrium concentration were found to be the rate limiting factors for polymer dielectrics discharge.