| Abstract: | Plasma-polymerized films of hexamethyldisiloxane were deposited onto various porous substrates having different pore sizes, and the gas permeability of these composite membranes was studied. In each membrane, permselectivity between oxygen and nitrogen was found, but the oxygen permeation rate was different with each substance tested. The minimum thickness of the plasma-polymerized film needed to plug all pores and show permselectivity is about five times the pore radius of the porous substrate. The maximum oxygen permeation rates of the permselective composite membranes are approximately proportional to the effective areas for the gas permeation and inversely proportional to the pore sizes. The composite membranes show high oxygen permeation rates in cases using porous glass hollow fibers which have small pore sizes and large surface porosity as porous substrates. In cases using polysulfone hollow fibers which have high permselectivity, the composite membranes show much higher permeability ratios of oxygen-to-nitrogen than do those of the porous glass hollow fibers. |
