Diffusion of Gases in Polyethylene Terephthalate

Journal of Applied Physics - Tập 34 Số 1 - Trang 13-20 - 1963
Alan S. Michaels1, W. R. Vieth1, J. A. Barrie1
1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts

Tóm tắt

Diffusion of helium, oxygen, nitrogen, argon, carbon dioxide, and methane in glassy and rubbery polythylene terephthalate has been studied in the range 25° to 130°C. Despite the abnormal solution behavior of these gases in the glassy polymer, the diffusion process is evidently normal and Fickian: Correlation of solubility constants for oxygen and nitrogen, obtained by the time-lag method, with data obtained by a static sorption method, indicates that glassy crystalline polyethylene terephthalate may be considered an isotropic diffusion medium. Diffusion is impeded purely geometrically by the presence of the crystallites, and the impedance factor is equal to the reciprocal of the amorphous volume fraction. In the rubbery crystalline state of the polymer, diffusion is Fickian and apparent activation energies for diffusion are larger than those in the glassy crystalline polymer. A model for diffusion in the glassy amorphous and crystalline polymers is proposed, assuming that the driving force for diffusion is the concentration gradient of dissolved molecules which are assumed to be in local equilibrium with molecules in the ``holes.'' The model predicts that actual diffusion constants and activation energies are larger than those experimentally measured. Thus, part of the observed difference between values of EDa in the glassy and rubbery states may be reconciled. Correlations of D and EDa with the square of gas molecular diameters are obtained in both the glassy and rubbery states. In the latter plots, the helium data fall above the correlations, showing evidence of partially non-activated diffusion in both states of the polymer.

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Tài liệu tham khảo

1959, J. Polymer Sci., 41, 53, 10.1002/pol.1959.1204113805

1961, J. Polymer Sci., 50, 413, 10.1002/pol.1961.1205015412

1959, J. Appl. Polymer Sci., 1, 340, 10.1002/app.1959.070010312

1959, J. Polymer Sci., 41, 307, 10.1002/pol.1959.1204113825

1924, Phys. Rev., 24, 575, 10.1103/PhysRev.24.575

1959, J. Phys. Chem., 63, 1080, 10.1021/j150577a012

1954, J. Am. Chem. Soc., 76, 3415, 10.1021/ja01642a015

1957, Trans. Faraday Soc., 53, 101, 10.1039/tf9575300101

1958, Trans. Faraday Soc., 54, 40, 10.1039/tf9585400040

1963, J. Appl. Phys., 34, 1, 10.1063/1.1729066

1961, Z. Naturforsch., 16, 37, 10.1515/zna-1961-0109

1959, J. Polymer Sci., 36, 21, 10.1002/pol.1959.1203613003

1955, J. Am. Chem. Soc., 77, 2172, 10.1021/ja01613a038

1960, J. Am. Chem. Soc., 82, 509, 10.1021/ja01488a001

1960, J. Am. Chem. Soc., 82, 513, 10.1021/ja01488a002

1951, J. Phys. Chem., 61, 178

1954, Zhur. Tekh. Fiz., 24, 797

1955, Zhur. Tech. Fiz., 25, 458

Thông tin
Thông tin xuất bản

Journal of Applied Physics

Tập 34 Số 1

13-20

Thông tin tác giả