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SYNOPSISPolyurethane prepolymers were prepared in ethylacetate from TDI and poly(oxypr0-pi1ene)glicols) (PE-PU) or poly(tetramethyleneglyco1adipate)diols (PES-PU) of different molecular weights (M). Homogeneous membranes were prepared by spreading the prepolymer solution added with a three, four or pentafunctional crosslinking agent, in the presence of stannous octoate as a catalyst. On increasing M, the PUS Tg decreases regularly in the range +30 to -47°C. PU's are amorphous with the exception of PES-PU obtained from highest M polyester diols. Permeability P, diffusivity D, solubility coefficient S of Nz, Oz, COz, CH,, CO were measured at T = 35OC (>T,). P, D, S do not depend on the crosslinker functionality, but mainly on M. P and D in PE-PU are linear function of T-T,, while in PES-PU the function is not linear. Gas solubility fulfills in general the regular solution theory. P, D, S of water vapor is also given. Permeability decreases in the order HzO > C02 > Oz > CH, > CO > N P . Some practical application based on particular selectivities is suggested.

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