PARTICLE-BEAM TREATMENT OF ORGANOSILICON GAS SEPARATION MEMBRANES - ANOVEL WAY OF CONTROLLING THEIR MASS-TRANSPORT PROPERTIES

Fast atom bombardment applied in the low keV energy range to organosil icon gas separation membranes was found to modify their mass transport properties in a controllable manner. In particular, asymmetric polyvi nyltrimethylsilane membranes and polydimethylsiloxane-based composite ones were treated by particle beams obtained from various gases like A r, He, H-2, and NH3, with particle energies of about 1 keV and doses o f about 10(15) particles cm(-2). In each case, improvements in the com ponent selectivities for various gas mixtures coupled with decreases i n the component permeances were obtained. The extent of modification o f the mass transport properties increased with increase of the calcula ted average depth of penetration of the bombarding particles. The modi fication of the mass transport properties was considered to take place as a result of compaction of the surface layer due to reactions like crosslinking and loss of pendant groups. (C) 1996 John Wiley & Sons, I nc.