Correlation between Fractional Free Volume and Diffusivity of CO2 Gas Molecules Through Neat and Blended Pebax Based Membranes

Gas transport properties of poly(ether-b-amide6) (under Pebax trademark) and poly(vinylran-dibutyl maleate) (PVAc-co-DBM) blends were measured. It was shown the CO2/CH4 selectivity (α)parameter enhanced twice of its primary amount with addition in P(VAc-co-DBM) wt%, however thepermeability (P) of CO2 had a reduction trend. Calculation of CO2 diffusivity (D) and solubility (S)indicated the reduction in permeability was because of diffusivity parameter reduction. To study thismatter more preciously fractional free volume (FFV) of membranes were calculated with two differentmethods. It was shown with P(VAc-co-DBM) increment, FFV of membranes have been reduced.Correlation between FFV and diffusivity of membranes confirmed gas transport data of preparedmembranes fitted properly in equations.

Keywords:

Poly(ether-b-amide) , Vinyl acetate- based copolymer , Blend membrane , Fractional free volume (FFV) , Carbon dioxide , Methane