Improvement of gas separation properties of polyurethane membrane using plasma grafting

In recent years, plasma treatments have presented good results since they offer high-tech efficiency with low waste generation. One of the most important characteristics of plasma methods is their action only on a thin surface layer, whereas the bulk of sample remains unchanged and the modified material keeps its chemical and mechanical properties. In this research, polyurethane membrane surface was modified by low- frequency plasma grafting with methacrylic acid and acrylamide monomers to alter solution-diffusion mechanism. We chose different parameters of plasma treatment and studied their effects toward maximum solubility, permeation, and selectivity. The grafting on the surfaces was characterized by water contact angle measurement and atomic force microscopy. After confirming a successful grafting, we studied the effect of surface modification on permeation of CH4 and CO2. Significant increase in CO2 permeation and about 32 percent increase in CO2/CH4 selectivity were observed. Better results were obtained for low powers and acrylamide grafted surface.