Gas transport properties of HTPB based polyurethane/cosalen membrane

Polyurethane (PU) membranes own high gas permeability but low selectivity. In the past, some attempts to increase the gas selectivity by modifying the polymer structure but the effort were unsuccessful. There were other attem pts to improve the gas separation by the addition of high affinity salt int o a membrane, It was reported that increasing the amount of oxygen carrier salt (cosalen) into a polycarbonate membrane did increase the selectivity o f oxygen to nitrogen especially at low temperature [G. Galland, T.M. Lam, J . Appl. Polym. Sci. 50 (1993) 1041]. An increase in salt addition reduced t he gas diffusivity but increased the diffusivity ratio of oxygen to nitroge n. In another study, it was also found that the addition of high oxygen-aff inity salt into a polycarbonate membrane did not greatly increase the solub ility ratio of oxygen to nitrogen but it significantly increased the diffus ivity ratio of oxygen to nitrogen [Rouh-Chyu Ruaan, Shih-Hsiung, Chen, Juin -Yih Lai, J, Membr. Sci. 135 (1997) 9]. In this study, the effects of oxyge n carrier salt namely, cosalen, in PU membrane on gas separation performanc e was examined. Gas diffusion and sorption properties were examined by sorp tion measurements and dual mode analyses. The dual mode analysis showed tha t the gas separation in PU membrane was dominated by gas diffusion rather t han gas sorption. The selectivity of O-2/N-2 was 8.6 and the oxygen permeab ility was 1.1 barrer for the PU membrane with 5 wt.% cosalen at 5 degrees C . The key issue of improving the gas separation performance of a polyuretha ne membrane was to increase the diffusivity ratio but not the solubility ra tio. (C) 2000 Elsevier Science B.V. All rights reserved.