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  • Physics  (1)
  • sorption rate curve  (1)
  • polyimide
  • time dependent diffusion
  • 1995-1999  (1)
  • 1970-1974  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 1829-1839 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sorption and diffusion of gases in poly(ethylene terephthalate) (PET) films have been measured by using a newly devised apparatus which gives the sorption rate curves from the initial to the equilibrium state. By analysis of sorption data for carbon dioxide in PET film, it was shown that the diffusion rate, as well as the equilibrium solubilities, could be explained by the dual-mode sorption mechanism proposed by Vieth et al. Constants of their equation were used in the analysis of our experimental results, in which the apparent diffusion coefficients were dependent on pressure. The result showed that the dual-mode sorption mechanism indeed applies to diffusion. The value of the real diffusivity obtained in amorphous PET was 5.7 × 10-9 (± 8%) cm2/sec in the range of pressure from 0 to 1 atm. It is believed that this apparatus has wide applicability, not only to diffusion of gases in polymers, but also to the measurement of surface properties, and can be used to study the morphology of a variety of polymers.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 777-784 
    ISSN: 0887-6266
    Keywords: permeation rate curve ; sorption rate curve ; polyimides ; chemical structure ; cohesive energy density ; gas separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The permeation rate curves and sorption rate curves of oxygen and nitrogen below 1.3 atm were measured for seven polyimides of which chemical structures were systematically changed. These rate curves were applied Fickian model curves. The Fick's law was found to hold from the pressure independencies of diffusion coefficients for both the experiments. The solubility was better described according to dual-mode sorption model rather than Henry-s law from the sorption experiments. The diffusivities of both the gases were correlated with packing density (reciprocal of specific free volume) of the polymer, except two polyimides. The packing density of these two polymers could not be successfully calculated from Bondi's method. However, all the diffusion coefficients decreased linearly with an increase in the cohesive energy density (CED), which was calculated by the group contribution method of van Krevelen. These results suggest that the gas diffusions in polyimides better correlate with CED than with the packing density. Therefore, the cohesive energy density may be considered as a more reliable indication of the efficient gas separation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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