Conditioning of fluorine-containing polyimides. 2. Effect of conditioning protocol at 8% volume dilation on gas-transport properties

The impact of conditioning on the permeability and permselectivity of CO2 a nd CH4 is discussed for two polyimide isomers that have been conditioned wi th carbon dioxide using several conditioning protocols. Partial depressuriz ation conditioning at pressures that would induce approximately 8% volume d ilation; resulted in up to 50% increases in the permeability, diffusivity, and solubility coefficients of the polyimide isomers. The para-connected is omer, GFDA-6FpDA, exhibited a greater conditioning effect following partial depressurization conditioning with CO2 at 8% volume dilation than did the meta-connected isomer, 6FDA-6FmDA. Conditioning of 6FDA-6FpDA followed by a n exchange with an equimolar mixture of CO2 and CH4 resulted in an increase in the methane permeability and a slight decrease in the permselectivity r elative to the film prior to conditioning.