ИСТИНА

Since invention of polytetrafluoroethylene (PTFE) in 1938th perfluoropolymers occupy some niche due to a combination of various properties (low surface and cohesive energies, high chemical resistance, low electroconductivity and permittivity, low refractive index, etc). Most of the perfluorinated homo- and copolymers (for instance, PTFE, Teflon FEP) are semicrystalline and, therefore, have low gas permeability and could not find application in membrane gas separation. Nevertheless, since 1980th and 90th three types of amorphous glassy polymers have been applied in industry and have attracted an attention as prospective materials for membranes (Teflons AF, Hyflons AD and Cytop). First two groups are copolymers of TFE and perfluorodioxoles while Cytop is aliphatic perfluorinated ring polyether. At the same time, a perfluorinated polyether with SO3H-groups (Nafion 117), a well-known material for H-conductive membranes, was investigated. Recent study by Mukaddam et al showed that Nafion 117 has unexpected potential in separation of fuel gas. During last years novel perfluorinated homo- and copolymers (i) polyhexafluoropropylene and its copolymer with perfluoromethylvinyl ether2, (ii) perfluoropropylvinyl ether3, and (iii) perfluorinated dioxolane-dioxolane copolymers4 were investigated. Teflons AF Hyflons AD Cytop Nafion Hydrocarbon gases and vapors are known to have lower solubility coefficients in perfluorinated polymers in comparison with those in “hydrocarbon” polymers. Therefore, perfluorinated polymers occupy favorable positions on Robeson diagrams (logarithmic dependencies of separation factor vs. permeability coefficient of a gas) for gas pairs containing hydrocarbons (He/CH4, N2/CH4, CO2/CH4, CO2/C2H6, etc) forming own trend. In presentation, we plan to discuss a nature of such unusual behavior of perfluorinated polymers and some aspects of their application in membrane gas separation. Mukaddam M. et al. Macromolecules, 2016, 49(1), 280-286. 2 Belov N.A. et al. J. Membr. Sci., 2011, 383(1-2), 70-77. 3 Belov N. et al. J. Membr. Sci., 2015, 495, 431–438. 4 Okamoto Y. et al. J. Membr. Sci., 2014, 471, 412–419.