The permeability of polymer films can be reduced dramatically with many layers of thin mineral flakes aligned parallel to the film's surface. For a film with a volume fraction φ of flakes of aspect ratio α, the permeability reduction is expected to be proportional to αφ for the dilute limit (φ ≪ 1 and αφ < 1) but proportional to (αφ)2 in the semi-dilute limit (φ ≪ 1 but αφ > 1). Permeabilities of hydrochloric acid and sodium hydroxide across films containing mica or vermiculite in polyvinyl alcohol agree with the second, semi-dilute prediction. Permeabilities of helium across films of montmorillonite in polyethylene glycol do as well. These improvements in barrier properties are independent of flake size, permeant and polymer chemistry.
Bibliographical noteFunding Information:
This work was largely supported by the Air Force Office of Scientific Research (grant F49620-01-1-0333). Other support came from the Department of Energy (grant DE-FG07-02ER63509), the Petroleum Research Fund (grant 39083-AC9), and the National Science Foundation (grant CTS 0322882).
- Polyvinyl alcohol