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General formula for bending beam determination of case II diffusion in polymer‐containing bilayer structures
Author(s) -
Jou JwoHuei,
Yang AnKuo,
Chang YingLun,
Jou JwoMin
Publication year - 1995
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.1995.070551103
Subject(s) - diffusion , bilayer , materials science , diffusion layer , polymer , polymer chemistry , substrate (aquarium) , bending , layer (electronics) , composite material , chemistry , membrane , thermodynamics , physics , biochemistry , oceanography , geology
An exact formula has been presented to correlate the bending curvature cariation ratio, Ω, of any given bilayer structure comprising a solvent‐swellable polymer layer with diffusion time, t , under case II diffusion. The formula can be used to determine the diffusion front velocity, v , for layered structures comprising a thick polymer film on a thin substrate or vice versa when subjected to solvent diffusion. According to this formula, there is little effect from plasticization or swelling in the transverse direction on the diffusion curve of Ω vs. t if the polymer layer to be investigated is relatively thin and its intrinsic hygroscopic strain ratio is less than unity. By using this model, the diffusion of N ‐methyl pyrollidinone (NMP) in a 18‐μm rodlike pyromellitic dianhydride p ‐phenylene‐diamine (PMDA‐PDA) polymide film, coated on a 75‐μm silicon substrate, is found to be case II with a diffusion front velocity of 1.84 × 10 ‐7 cm/s. © 1995 John Wiley & Sons, Inc.