Kinetics of vapor and liquid transport in glassy polyblends of polystyrene and poly (2,6‐dimethyl 1,4‐phenylene oxide) Part II

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Abstract
The kinetics of n‐hexane vapor and n‐hexane liquid sorption in solution cast films of polystyrene, poly(phenylene oxide), and blends of these homopolymers were studied over a significant range of temperature and penetrant activity. The kinetics of concomitant solvent crazing, apparent at high penetrant activities, were also monitored. In all cases the kinetics of sorption and crazing obeyed predominantly Case II or relaxation‐controlled behavior. Although the rates of crazing and sorption at high activities was much more rapid in the homopolymers than in the blends, the sorption rate at lower penetrant activities increased monotonically with increasing poly(phenylene oxide) content.These kinetic results qualitatively superimpose upon the equilibrium relationships reported in Part I of this series. Specifically, at a fixed temperature, the rate of crazing was virtually a unique function of equilibrium n‐hexane content independent of polymer composition and largely independent of penetrant activity. The coupling between rate of sorption and equilibrium penetrant content was dramatic. In limiting cases, the sorption rate increased by a factor of 10,000 apparently due to a twofold increase in equilibrium penetrant concentration. This seemingly complicated kinetic behavior is explained rather simply in terms of the equilibrium relationships between organic penetrants and polymeric glasses developed and interpreted in the first part of this series.
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