Diffusion and sorption of gases in poly(ethylene terephthalate)

Abstract

AbstractThe sorption and diffusion of gases in poly(ethylene terephthalate) (PET) films have been measured by using a newly devised apparatus which gives the sorption rate curves from the initial to the equilibrium state. By analysis of sorption data for carbon dioxide in PET film, it was shown that the diffusion rate, as well as the equilibrium solubilities, could be explained by the dual‐mode sorption mechanism proposed by Vieth et al. Constants of their equation were used in the analysis of our experimental results, in which the apparent diffusion coefficients were dependent on pressure. The result showed that the dual‐mode sorption mechanism indeed applies to diffusion. The value of the real diffusivity obtained in amorphous PET was 5.7 × 10−9 (± 8%) cm2/sec in the range of pressure from 0 to 1 atm. It is believed that this apparatus has wide applicability, not only to diffusion of gases in polymers, but also to the measurement of surface properties, and can be used to study the morphology of a variety of polymers.