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Measuring Gas Permeability and Diffusion Coefficients in Thin Polymer Films

IP.com Disclosure Number: IPCOM000089345D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Lee, W: AUTHOR [+2]

Abstract

The classical techniques for measuring the gas permeability of thick films (> 1 mil) cannot be used to evaluate the permeability and diffusivity of gases or vapor in thin films (

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Measuring Gas Permeability and Diffusion Coefficients in Thin Polymer Films

The classical techniques for measuring the gas permeability of thick films (> 1 mil) cannot be used to evaluate the permeability and diffusivity of gases or vapor in thin films (</= 1 Micron) deposited on an impermeable substrate.

An apparatus and technique have now been developed by which the important transport properties of thin films can be measured readily and precisely. The apparatus consists of an oscillating crystal microbalance upon which is deposited a thin film of a chemical sink. The chemical sink should be a substance which is specifically reactive with the diffusing gas or vapor of interest. For example, silver or sodium metal is a good sink for H(2)S gas. Subsequent to the coating with the chemical sink, the polymer film is applied on the microbalance crystal by either spin coating or doctor blading a polymer solution on it, followed by an appropriate annealing process.

To protect the reactive sink from the ambient air, the polymer coating process is done in an inert atmosphere, i.e., nitrogen or helium.

The coated microbalance crystal is then placed in an environmental chamber containing the vapor or gas of interest, and the weight gain of the polymer- chemical sink composite is monitored with time. The gas permeability and diffusivity are computed from the characteristic weight gained - time curve of the polymer-chemical sink composite.

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