A series of amine-containing polyurethanes and poly(urethane-urea)s based on 4,4'-diphenylmethane diisocyanate and either poly(ethylene glycol) of molecular weights 400 or 600 were prepared as gas separation membranes. The amine functional groups of N-methyldiethanolamine (MDEA) and/or tetraethylenepentamine (TEPA) were introduced into the hard segment as a chain extender. The gas transport data of He, H2, O2, N2, CH4 and CO2 in these polymer membranes were determined by using the Barrer's high-vacuum technique and the time-lag method. The restriction of chain mobility has been shown by the formation of hydrogen bonding in the soft segment and hard-segment domains, resulting in the increase in the density, glass transition temperature of soft segments (T(gs)). The separation mechanism of various gas pairs used in industrial processes is also discussed. Effect of pressure on permeability of the gases above and below T(gs) was studied. It was found that the gas permeability increased or decreased with upstream pressure above T(gs), and should be described by a modified free volume model. On the other hand, the condensable CO2 exhibits a minimum permeability at a certain upstream pressure below T(gs). The permeability of He and H2 were pressure independent above and below the T(gs).
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physical and Theoretical Chemistry
- Filtration and Separation