barrier thickness is a factor?  


Posted by Thomas LeBlanc on March 26, 2004 at 21:06:00:

Hello,

I'm new to investigating water vapour diffusion in polymers and composites, and I'm hoping someone can answer for me what I think is a basic question...but unfortunately I haven't been able to find a definitive answer! Here is a detailed scenario of the question:

Assume I have a cube that is hermetically sealed and contains nitrogen at atmospheric pressure. The exception is a small "window" on one side of the cube. This "window" is a film of UV-cured epoxy adhesive. (This may sound like a strange setup, but it's the best way for me to describe the potential problem I need to solve)

I'm interested in determining if, at some "steady state" condition, the rate of water vapor molecules which will desorb from the inner surface of the "window" (i.e., can get into the "inner sanctum" of the cube) is at all affected by the THICKNESS of the adhesive film. The surface area of the window would not change, just the thickness of the polymer film. I understand that time lag is affected by the film thickness, but what about at a "steady state" condition?

Thank you very much in advance for any response!

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