Prediction of gas permeability of heterogeneous polymer blends

A recently introduced predictive scheme is used to calculate the permeability of various types of heterogeneous polymer blends, which are characterized by the ratio of the permeability of constituents in the range 10-10,000. The scheme combines a two-parameter equivalent box model and the data on the continuity of constituting phases acquired by modifying equations proposed by the percolation theory; it takes into account the permeability of components and the interval of phase duality (co-continuity) delimited by the critical volume fractions of components v1cr and v2cr. The scheme can be used in two ways: (i) permeability of blends predicted by using the `theoretical' value of parameters v1cr = v2cr = 0.16 should be regarded as a first approximation which may not well approximate experimental data due to the fact that real v1cr and v2cr are affected by relative viscosities of the components, interfacial energy, conditions of blend mixing, phase structure coarsening, etc.; (ii) conversely, by fitting experimental data, it is possible to determine v1cr and v2cr for the studied system; thus the scheme can be alternatively viewed as an efficient tool for phase structure analysis of polymer blends.