Membranes for gas separation were prepared by various methods and used for the oxygen enrichement from air. Pressure had little effect on the selectivity and permeability. But the selectivity decreased and the permeabity increased with temperature.
The polysulfone support membrane with good permeability was prepared via a phase inversion process. The dry phase inversion time had an influence on the structure of the support layer: fast inversion time (0 and 1 min) produced finger-type macrovoids and slow inversion time (2 min) produced homogeneous spherical cell structure.
Thin composite membranes were prepared by coating poly (dimethyl siloxane) as thin layer on the above polysufone support. For air separation the selectivity increased and the permeability decreased with the dry phase inversion time in the preparation of polysulfone supports. Particularly when the polysulfone of slow inversion time was used, the selectivity was greater two times than that of the homogeneous poly (dimethylsiloxane) membrane and the permeability was comparable each other.
Thin composite membrane was prepared by coating the mixture of poly (dimethylsiloxane) and poly(vinylmethoxysiloxane) on the polysulfone support of slow inversion time. The permeability of the membrane increased with the amount of poly (vinylmethoxysiloxane) but the selectivity was little affected.
The glassy poly (4-vinylpyridine) membrane was known to have higher selectivity and lower permeability as compared with the rubbery poly (dimethylsioloxane) membrane.