CARBON-DIOXIDE SORPTION AND TRANSPORT IN POLYCARBONATE

In this paper the solubility, permeability, and diffusion time lag for carbon dioxide in polycarbonate are reported at 35 degree C for pressures ranging from 1 atm to 23 atm. The solubility data are very well described by the dual sorption mechanism model, Henry's law plus Langmuir adsorption, proposed for glassy polymers. Both the permeability and time lag decrease with increased CO//2 pressure. The data have been quantitatively analyzed in terms of partial immobilization model, and the results suggest for polycarbonate at 35 degree C that the CO//2 sorbed by the Langmuir portion of the isotherm behaves as if it has only about 10% of the mobility of the gas sorbed by the Henry's law part of the isotherm. The results have been interpreted in terms of a concentration-dependent diffusion coefficient which is shown to be mathematically equivalent to the partial immobilization model.