Gas sorption and transport in a copolyester and its blend with polycarbonate

AbstractSorption and transport measurements for various gases were made with a copolyester formed from 1,4‐cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids. Similar observations for the miscible blends of this copolyester with polycarbonate were made using carbon dioxide. All of these results are described well by dual sorption‐dual mobility models which have been used effectively for other gas‐glassy polymer systems. The sorption and transport parameters deduced experimentally from these systems have been correlated and interpreted in terms of applicable theories. For the blends, the Henry's‐law sorption parameter has been used to deduce a reasonable value of the interaction parameter for the polycarbonate‐copolyester blend system from the Flory‐Huggins theory of mixtures. The Langmuir capacity term from the dual‐sorption model is accurately related to the unrelaxed volume of the glass. Negative deviations of permeability and diffusion coefficients from simple additivity relations were observed and qualitatively interpreted to result from the decrease in volume on mixing for the blends.