Physical Aging and Carbon Dioxide Plasticization of Thin Polyetherimide Films

Industrial gas separation membranes have selective dense layers with thicknesses around 100 nm. It has long been assumed that these thin layers have the same properties as thick (bulk) films. However, recent research has shown that thin films with such thickness experience accelerated physical aging relative to bulk films and, thus, their permeation properties can differ significantly from the bulk. This paper explores the aging and carbon dioxide plasticization behavior of this new polyethermide and compares the results with those for PSF and Matrimid® 5218 from the previous work. Particular attention is devoted to the permeation response of thin films for a variety of CO₂ conditions due to the current strong interest in CO₂ related separations, such as the removal of CO₂ from natural gas and flue gases. The CO₂ plasticization of Extem thin films is proven to be a function of film thickness, aging time, exposure time, pressure and prior history.