Prediction of the gas permeability of heterogeneous polymer blends

A recently introduced predictive scheme is used to calculate the permeabili ty of various types of heterogeneous polymer blends, which are characterize d 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 th e continuity of constituting phases acquired by modifying equations propose d by the percolation theory; it takes into account the permeability of comp onents and the interval of phase duality (co-continuity) delimited by the c ritical volume fractions of components nu(1cr) and nu(2cr). The scheme can be used in two ways: (i) permeability of blends predicted by using the "the oretical" value of parameters nu(1cr) = nu(2cr) = 0.16 should be regarded a s a first approximation which may not well approximate experimental data du e to the fact that real nu(1cr) and nu(2cr) are affected by relative viscos ities of the components, interfacial energy, conditions of blend mixing, ph ase structure coarsening, etc.; (ii) conversely, by fitting experimental da ta, it is possible to determine nu(1cr) and nu(2cr) for the studied system; thus the scheme can be alternatively viewed as an efficient tool for phase structure analysis of polymer blends.