Mechanisms of gas permeation through polymer membranes. Progress report, April 30, 1980-March 31, 1981

Technical Report · Wed Apr 01 04:00:00 EST 1981

OSTI ID:6206921

Stern, S A; Kulkarni, S S; Mauze, G R

The objective of this study is to assess the validity of a free-volume model of gas permeation through nonporous polymer membranes. This model provides a formalism for the prediction of permeability coefficients for pure gaseous penetrants and their mixtures as a function of both pressure and temperature. Three characteristic free-volume parameters, designated A/sub d/, B/sub d/, and ..gamma.., are required for this purpose. The three parameters were determined for CH/sub 4/ in polyethylene from diffusivity and solubility measurements with polymer rods between 5 and 35/sup 0/C, and at pressures of up to 40 atm. Permeability coefficients for CH/sub 4/ estimated from the free-volume model by means of these parameters were found to be in satisfactory agreement with experimental values obtained from independent permeability measurements with thin polyethylene membranes. A new and more rigorous method of estimating permeability coefficients for gas mixtures from the free-volume model has been developed. Permeability coefficients were calculated by this method for the components of equimolar C/sub 2/H/sub 4/-C/sub 3/H/sub 8/, CO/sub 2/-C/sub 2/H/sub 4/, and CO/sub 2/-C/sub 3/H/sub 8/ mixtures and of a 74.9% CO/sub 2/-25.1% C/sub 2/H/sub 4/ mixture. Satisfactory overall agreement was found between these coefficients and values obtained experimentally between 20 and 50/sup 0/C and at pressures of up to 28 atm. Simple linear correlations have been found for the free-volume parameters A/sub d/, B/sub d/, and ..gamma.. as a function of certain basic physicochemical properties of penetrants and penetrant-polymer systems. These correlations can be determined with only a few measurements with a given polymer, and are useful for estimating values of A/sub d/, B/sub d/, and ..gamma.. for other penetrants in the same polymer. The free-volume model has bee modified and extended to describe gas permeation through both rubbery and glassy polymer membranes. The extended model should be applicable to porous as well as nonporous membranes.

• Research Organization: Syracuse Univ., NY (USA). Dept. of Chemical Engineering and Materials Science
• OSTI ID: 6206921
• Report Number(s): DOE/ER/05015-1; ON: DE81025637
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360404 -- Materials-- Polymers & Plastics-- Physical Properties-- (-1987)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400105* -- Separation Procedures
ALKANES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
COMPARATIVE EVALUATIONS
DIFFUSION
DISPERSIONS
ETHANE
FLUIDS
GASES
HYDROCARBONS
MEDIUM PRESSURE
MEDIUM TEMPERATURE
MEMBRANES
METHANE
MIXTURES
ORGANIC COMPOUNDS
ORGANIC POLYMERS
OXIDES
OXYGEN COMPOUNDS
PERMEABILITY
POLYETHYLENES
POLYMERS
POLYOLEFINS
PRESSURE DEPENDENCE
PROPANE
RESEARCH PROGRAMS
RODS
SOLUBILITY
TEMPERATURE DEPENDENCE