Dual‐mode sorption and transport of sulfur dioxide in kapton polyimide

Abstract

Abstract The kinetics and equilibria of SO 2 sorption in Kapton polyimide film have been studied at temperatures from 25 to 55°C and equilibrium sorption pressures up to 0.76 atm. The data are described well by the dual‐mode model of sorption and transport in glassy polymers. The assumption of “partial immobilization” is required to correlate the transport data: the mobility of the Langmuir component of the sorbed population relative to the Henry's‐law component is close to zero at 25°C, and increases to roughly 5% of the Henry's‐law component mobility at 55°C. The heat of sorption is anomalously low, suggesting the presence of residual solvent in the film, a suggestion confirmed by annealing studies. However, the study also shows that partial removal of the residual has a relatively minor effect on the measured SO 2 sorption level and transport rates at 55°C.