Glassy polymer membranes plasticization

Semenova SI, Smirnov SI, and Ohya H. Performances of glassy polymer membranes plasticized by interacting penetrants. J Membr Sci 2000 172 75-89. 

When the interaction between one penetrant and the polymer is not affected by the presence of another penetrant, the pure-component permeabilities of the two penetrants in the mixture can be used in Equation 7. For rubbery polymers at low penetrant partial pressures, this assumption of independent-permeation appears satisfactory (19-20). It does not, however, appear to hold in general for glassy polymer membranes (12,13,21-25). Moreover, it also has been shown that plasticization of both rubbery (26) and glassy (27) polymers can occur at higher penetrant activities. 

Thermal annealing is a well-known process to stabilize the glassy polymer membrane, which induces a densiflcation of the polymer matrix and leads to a restricted chain mobility. Thns, the membrane plasticization cansed by the absorbing of gas and liquid molecules is hindered [61]. 

Sanders, E.S. (1988) Penetrant-induced plasticization and gas permeation in glassy polymers. Journal of Membrane Science,... 

It is generally accepted that mass transport in dense polymer membranes takes place according to the well-known solution-diffusion mechanism [18,19]. For non-swelling and non-plasticizing species the amount of penetrant that can dissolve in the glassy polymer matrix depends on the available sorption sites and often a typical dual mode sorption behaviour is observed [20]. The number of Langmuir sorption sites is strongly related to the free volume distribution of the sample. 

A. F. IsmaU, W. Loma, Penetrant-induced plasticization phenomenon in glassy polymers for gas separation membrane, Sep. Pur. Tech., 27, 173-194 (2002). 

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