New apparatus for gas permeability, diffusivity and solubility assessing in dense polymeric membranes

Apparatus for consecutive measurements of permeability, diffusivity and solubility of vapors in polymer film during a single experiment was developed. The main advantage of this sweeping-gas apparatus with a new type of a permeation cell is the possibility to determine an amount of permeates sorbed in a membrane in the steady state of a vapor permeation process without any need of manipulation with the membrane. Permeate sorption data in the steady state provide important information about transport mechanism in polymeric membranes. Performance of the cell is illustrated on an example of toluene vapor permeation measurements through a low-density polyethylene (LDPE) membrane at 30 °C. The new apparatus provides transport parameters (permeant solubility, diffusivity as well as polymer permeability) with high sensitivity and good reproducibility. Errors in transport parameters determination directly attributable to this technique seldom exceed 7%.