In-Situ Observation of Permeation Behavior and Structural Analysis of Polyimide Membrane with Electrical Properties

Abstract

An ethanol aqueous solution was made to permeate into a polyimide membrane of three-dimensional porous structure, and the permeation behavior of the solution and the structure of the membrane were determined in situ based on the electrical characteristics. The experiment was carried out with a polyimide porous membrane having a porosity of 70%. The permeation rate of the solution into the membrane was calculated from the relationship between the time after drops of the ethanol aqueous solution began to be applied and the electrostatic capacitance. As a result, it was found that the solution quickly permeated into the porous membrane after drops began to be applied and then gradually filled the whole membrane. Similarly, the measured permeability of the surface of the polyimide porous membrane facing the air and the surface facing the substrate and SEM observation showed that the air-facing surface had a large opening area so that a solution easily permeates. As the rings of the imide group progressively opened due to alkali treatment, the relaxation time of the porous membrane became longer.