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Sorption of organic liquids and vapors by rigid PVC
Author(s) -
Berens Alan R.
Publication year - 1989
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1989.070370405
Subject(s) - sorption , gravimetric analysis , kinetics , volume fraction , thermodynamics , glass transition , solvent , fick's laws of diffusion , thermal diffusivity , diffusion , chemistry , vinyl chloride , polymer chemistry , materials science , polymer , organic chemistry , adsorption , copolymer , physics , quantum mechanics
The effects of activity and solvent strength of a number of organic penetrants upon their sorption kinetics and equilibria in poly(vinyl chloride) have been studied by gravimetric vapor and liquid sorption experiments at 30°C. For each solvent, the relation of equilibrium sorption to activity is well approximated by the Flory–Huggins equation with a characteristic value of the interaction parameter χ. The glass transition temperature T g is depressed in direct proportion to the volume fraction of solvent absorbed; the composition corresponding to a T g of 30°C, C g (30°C), is in the range of 0.22–0.30 volume fraction for several common solvents. The form of the sorption kinetics varies with the ratio of the equilibrium sorption to C g , and thus depends on the combined effects of χ, solvent activity, and plasticizing action. When the equilibrium sorption is less than about C g /2, kinetics are Fickian, with the very low diffusivities typical of the glassy state; for sorption values between C g /2 and C g , anomalous kinetics are observed; and when the sorption is greater than C g , transport in thin PVC films follows Case II kinetics. At high sorption levels, increasing film thickness produces a shift of the kinetics toward Fickian form with apparent diffusivity values typical of rubbery polymers.