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 CO 2 and CH 4 is discussed for two polyimide isomers that have been conditioned with carbon dioxide using several conditioning protocols. Partial depressurization conditioning at pressures that would induce approximately 8% volume dilation; resulted in up to 50% increases in the permeability, diffusivity, and solubility coefficients of the polyimide isomers. The para-connected isomer, 6FDA-6F p DA, exhibited a greater conditioning effect following partial depressurization conditioning with CO 2 at 8% volume dilation than did the meta-connected isomer, 6FDA-6F m DA. Conditioning of 6FDA-6F p DA followed by an exchange with an equimolar mixture of CO 2 and CH 4 resulted in an increase in the methane permeability and a slight decrease in the permselectivity relative to the film prior to conditioning.