Ethylbenzene solubility, diffusivity, and permeability in poly(dimethylsiloxane)

✍ Scribed by S. V. Dixon-Garrett; K. Nagai; B. D. Freeman

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 226 KB
• Volume: 38
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(20000601)38:11<1461::aid-polb60>3.0.co;2-h

✦ Synopsis

The pure-gas sorption, diffusion, and permeation properties of ethylbenzene in poly(dimethylsiloxane) (PDMS) are reported at 35, 45, and 55 °C and at pressures ranging from 0 to 4.4 cmHg. Additionally, mixed-gas ethylbenzene/N 2 permeability properties at 35 °C, a total feed pressure of 10 atm, and a permeate pressure of 1 atm are reported. Ethylbenzene solubility increases with increasing penetrant relative pressure and can be described by the Flory-Rehner model with an interaction parameter of 0.24 Ϯ 0.02. At a fixed relative pressure, ethylbenzene solubility decreases with increasing temperature, and the enthalpy of sorption is Ϫ41.4 Ϯ 0.3 kJ/mol, which is independent of ethylbenzene concentration and essentially equal to the enthalpy of condensation of pure ethylbenzene. Ethylbenzene diffusion coefficients decrease with increasing concentration at 35 °C. The activation energy of ethylbenzene diffusion in PDMS at infinite dilution is 49 Ϯ 6 kJ/mol. The ethylbenzene activation energies of permeation decrease from near 0 to Ϫ34 Ϯ 7 kJ/mol as concentration increases, whereas the activation energy of permeation for pure N 2 is 8 Ϯ 2 kJ/mol. At 35 °C, ethylbenzene and N 2 permeability coefficients determined from pure-gas permeation experiments are similar to those obtained from mixed-gas permeation experiments, and ethylbenzene/N 2 selectivity values as high as 800 were observed.