Thickness characterization of thin polymer nanocomposite oxygen barrier

Thin films of sodium montmorrilonite clay and cationic Polyacrylamide have been produced by alternately dipping a plastic substrate into dilute aqueous mixtures containing each ingredient. After 30 clay-polymer layers have been deposited, the resulting transparent films exhibit an oxygen transmission rate below the detection limit of commercial instrumentation (< 0.005 cm 3/m2/day). This level of oxygen barrier, which is unprecedented for a clay-filled polymer composite, is believed to be due to a nano-brick wall microstructure comprised of completely exfoliated clay in a polymeric mortar. This brick wall creates an extremely tortuous path at thicknesses below 500 nm. Thickness measurement of these thin films is very challenging, requiring several techniques to confirm accuracy. Ellipsometry, weight measurement, and electron microscopy were used in the present study to obtain accurate thickness. With an optical transparency greater than 90% and potential for microwaveability, this thin film composite is a good candidate for foil replacement in food packaging and may be useful for flexible electronics packaging.

Thickness characterization of thin polymer nanocomposite oxygen barrier Conference Paper