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:
The diffusion coefficient at zero concentration and the free volume parameters in Fujita's free volume theory were measured for benzene, hexane, and heptane in modified polyethylene films using an unsteady-state absorption technique. Films were modified by gamma irradiation, solvent conditioning, and post- and preirradiation conditioning. Dc=0 was found to drop with irradiation, the drop being larger the larger the molecular size of the diffusing molecule. A relationship for the dependance of Dc=0 on the crosslink density is proposed. Solvent conditioning led to an increase in Dc=0 directly proportional to the swelling power of the conditioning agent and to the molecular size of the diffusant molecule. In most cases, combined treatment resulted in an increase in Dc=0, the extent of which was dependent upon the relative effect of the swellant and the irradiation dose. In all cases, postirradiation conditioning led to values of Dc=0 higher than those obtained by preirradiation conditioning. The fractional free volume of the polymer was found to decrease with irradiation, showing a marked drop at low doses when reaching a state where the dose was of small effect. Changes in f(0,T) with conditioning and with combined treatment followed the same general pattern as Dc=0. β(T) was unaffected by any kind of treatment studied. Bd changed in practically the same manner as f(0,T) but in the opposite direction. A method is proposed for the optimum choice of a membrane modification procedure based on solubility and diffusivity results.
Additional Material:
8 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1979.070230623
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