Gas permeability of block copolymers of styrene and butadiene

The permeability of styrene-butadiene block copolymer foils with different composition prepared by casting and pressing has been investigated for the gases Ar, CO₂, and CH₄ at pressure difference of 400 mbar and at the temperature range 298 T K] 333.The permeation process can be described by the solution diffusion mechanism. The diffusion coefficients decrease in the sequence of the gases Ar, CO₂, and CH₄ and the solubility coefficients increase in the sequence Ar, CH₄, CO₂.The dependence of the permeability on the composition of the block copolymer can be interpreted by the help of percolation theory and the effective medium theory. It follows the critical volume fraction of the percolation of the transport phase _PB ^c (= 0,23) and the coordination numberz (= 4) giving an information concerning the multiphase structure of the block copolymer.Presented in part at the 33^rd Annual Meeting of the Colloid-Gesellschaft, Graz, Austria, September 14–16, 1987.