ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A method of analyzing permeation data has been developed which permits the diffusion coefficient D, its variation with concentration, and the solubility coefficient to be determined from a single experiment on the permeation of a vapor through a membrane when diffusion is known to be Fickian. There is evidence that in the range from the glass temperature Tg to (Tg + 20°C.) the diffusion of an organic vapor into a polymer is not always Fickian. In such a case a single permeation experiment gives the limiting value of D at zero vapor concentration. If the sorption isotherm is determined, two or three permeation experiments give sufficient information to characterize the concentration dependence of D and to predict a “Fickian time lag.” The difference between the observed and the predicted time lag is the mean relaxation time of the time-dependent factors in the non-Fickian permeation. When there is a transient period of rapid permeation at the beginning of an experiment a plot of permeation rate against logarithmic time permits another relaxation time to be defined. By comparing these relaxation times with the mechanical characteristics of the polymer the time-dependent mechanisms of permeation may be identified.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1965.070090310
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