The diffusion of gases and vapors in rigid PVC

Gravimetric sorption rate measurements have been carried out for (CO 2 , H 2 ), and ten C 1 ‐C 6 organic vapors at low concentrations (≤ 0.2%) in PVC films and uniform‐particle powders at 30°C. The dominant transport process in all cases appears to be Fickian diffusion. A distinguishable contribution of relaxation‐controlled swelling was observed for the more soluble vapors, such as acetone and benzene. A significant contribution of surface adsorption to the total sorption process was detected only for the n‐alkanes, among the penetrants studied. Diffusion coefficients, determined from half‐sorption times and polymer dimensions, range from 4 × 10 −8 cm 2 /sec for H 2 O to 1.5 × 10 −15 cm 2 /sec for n‐hexane. Diffusivities determined in this study, in combination with those for gases reported by Tikhomorov, et al. (Makromol. Chem. 118 177 (1968)), define a continuous curve, covering more than nine orders of magnitude, when plotted as a function of the molar volume constant, b, of the van der Waals equation of state for gases and vapors.