Poly(tetrafluoroethylene) Sputtered Polypropylene Membranes for Carbon Dioxide Separation in Membrane Gas Absorption

This work presents a study of the use of polypropylene (PP) membranes that have been sputtered with poly(tetrafluoroethylene) (PTFE) in a radio frequency plasma reactor. Plasma treatment results in the deposition of an ultrathin microporous coating which has a high degree of fluorination and nano- and microscale roughness. The treated membrane maintains similar pore characteristics and a similar thickness to untreated PP, and therefore, it is likely that the treatment film provides a negligible resistance to CO2 mass transfer relative to that of the bulk PP membrane. The absorption results presented in this paper show that the plasma-treated membrane has a comparable or superior performance to that of PTFE for CO2 mass transfer into monoethanolarnine solvent. A flat sheet membrane configuration is used to test the properties of the material and to show that the treated membrane has a comparable CO2 mass-transfer rate to PTFE after 25 days of solvent exposure. Results suggest that all membrane materials are at least partially wetted but that the extent of wetting is lower in the PTFE and plasma-sputtered membrane, relative to untreatred polypropylene.