VOC sorption in glassy polyimides—Measurements and modeling

The sorption behavior of volatile organic compounds (VOCs) in polymeric membrane materials such as polyimide, has a strong effect on the separation efficiency of dense polymeric nanofiltration membranes. To investigate the sorption behavior, this work presents gravimetrically measured and modeled sorption profiles for a series of VOCs (like n-hexane, ethanol, toluene, 2-propanol, and ethyl acetate) in two polyimides (P84 and Matrimid) at 25 °C. The experimental results show significant differences in the sorption speed of the VOCs in the two polyimides. The sorption of toluene, ethyl acetate, and ethanol in Matrimid is very fast compared to the sorption of 2-propanol, but the sorption in P84 is very slow for all the VOCs studied. The sorption behavior of the polyimide/VOC systems has been modeled using an improved one-dimensional Maxwell–Stefan diffusion model. The measured and modeled results provide detailed insight into the specific sorption behavior of the VOCs in the glassy polyimides P84 and Matrimid.