Permeability of High-polymer-films to Gases and Vapors

V. Dependency of Permeability Coefficient on Film Thickness

Abstract

Dependency of permeability coefficient (P) on film thickness was examined with the results as follows:(1) Measurement, made on the cup method for the permeation of vapor through high polymer film to which the vapor has affinity, indicated that P increased with increase in thickness of the film.(2) Residual solvent, residual strain and difference in structure of the inner and surface parts of the film, hitherto regarded as probable causes for the phenomenon mentioned in (1) above, were turned out to have little influence.(3) In the process of permeation, one side of the film is in “wet” condition and the other in “dry” condition. The proportion of the former increases with increasing the film thickness. This fact in the most probable cause for the increase in P with increase in the film thickness.