Gas-Driven Porosity Control in Cellulose Acetate Membranes: Comparing Nitrogen and Carbon Dioxide for Micropore Formation

Cellulose acetate (CA) is a widely used porous material in various industrial applications, and its processing methods have evolved. This study presents a novel approach to enhancing pore formation efficiency by substituting nitrogen (N₂) with carbon dioxide (CO₂), a gas with a higher quadrupole moment. This method was employed to fabricate lactic acid-plasticized CA membranes coated on polypropylene substrates, enabling control over pore size and porosity. Surface morphology was analyzed using scanning electron microscopy to observe structural changes before and after gas permeation, with respect to the type of gas used. Fourier-transform infrared spectroscopy was used to assess molecular changes induced by lactic acid addition and to investigate gas-specific differences in pore formation. Thermal stability was evaluated via thermogravimetric analysis in relation to pore development. Additionally, the porosity, Gurley values, and gas permeance were measured to compare the effects of N₂ and CO₂ on the physical properties of the membranes.