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Permeation of gases across the poly(chloro‐ p ‐xylylene) membrane
Author(s) -
Tanioka Akihiko,
Fukushima Noriaki,
Hasegawa Koichi,
Miyasaka Keizo,
Takahashi Noboru
Publication year - 1994
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.1994.070540208
Subject(s) - permeation , xylylene , membrane , permeability (electromagnetism) , activation energy , glass transition , gaseous diffusion , materials science , diffusion , polymer , chemistry , analytical chemistry (journal) , polymer chemistry , thermodynamics , composite material , chromatography , biochemistry , physics , electrode
Gas permeabilities across poly(chloro‐ p ‐xylylene) (parylene C) films are measured with different thicknesses of 20.2, 10.0, 8.9, 4.6, 3.4, and 1.0 μm. Measurements were carried out below 1 atm and between 10 and 80°C, which are under the glass transition temperature. The temperature and pressure dependencies of the permeability and the apparent diffusion coefficients were measured. If the membrane thickness is larger than 8 μ, the gas‐transport mechanism is solution–diffusion, which implies that it is pinhole‐free, because the pressure dependency of the permeability cannot be found and the apparent activation energy of permeation and diffusion are observed. If the membrane thickness is less than 8 μ, the gas transport mechanism is pore flow combined with solution–diffusion flow because gas may penetrate both the porous area and the polymer matrix. The thinner the membrane, the higher is the permeability coefficient, since the diameter and number of pores increase with decrease of the membrane thickness. The gas permeability coefficient has different values at the same pressure or temperature. As this film is in the glassy state, it should be explained using the average ordering parameter (ξ), which is a function of temperature, pressure, gas concentration, and time. © 1994 John Wiley & Sons, Inc.