Barrer-Petropoulos model

Fig. 25. Permeability of pure CO2 in poly(phenylene oxide). The solid lines represent (a) the Koros and Paul, (b) the Petropoulos model, and (o) the Barrer model. To convert MPa to atm, multiply by 10.1 Barrer = 10 ° [cm (STP)cm]/(cm s cm Hg) = 0.335 mmol/(m s TPa).

Fredrickson and Helfand incorporated coupling terms in the transport equation and showed that "these terms provide mobility to molecules that are absorbed into microvoids, even if the molecules have an intrinsic diffusion coefficient in the hole phase that vanishes." These investigators proposed experiments that could provide information on the size and topological connectivity of microcavities (51). Related studies have also been made by Chern, Koros, et al. (52) and by Barrer (53). However, Petropoulos (54) has expressed the opinion that the treatment of Fredrickson and Helfand (51 ) as well as that of Barrer (53) "introduces more diffusion parameters than can reasonably be expected to be measurable on the basis of past experience". Petropoulos also showed that these treatments impose certain limitations on the physical meaning of the diffusion parameters. In the same study, Petropoulos has examined the modification of his dual-mode sorption model ( 5) which are necessary if the Langmuir domains are sufficiently extensive to constitute a macroscopically recognizable phase rather than scattered individual sites (or microcavities) (54). ... 

Petropoulos, Koros and Paul, and Barrer models. Mixed-gas permeability is depressed relative to the pure-gas values for both components. As expected, the mixed-gas Barrer model predicts lower permeability for both components than either of the simpler models. 

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