A Deep Dive into the Non-Fickian Behavior of Metalized Films
For various applications, metalized films should have their water vapor transmission rate (WVTR) examined alongside other barrier properties. However, whether historically or today, measuring WVTR of metalized films has proved challenging, particularly in obtaining repeatable values due to the film’s mysterious Non-Fickian behavior (i.e. the material changes with increasing humidity exposure).
Recently, MOCON tested WVTR of metalized OPET and metalized BOPP. The studies were conducted on one MOCON Legacy permeation analyzer PERMATRAN-W 3/33, and two Next Generation analyzers, the PERMATRAN -W 3/34 and AQUATRAN 3/38. The WVTR studies were conducted at the following test conditions: 37.8C, with RH levels of 50%, 75%, 85%, 90% and 100%.
Both OPET and BOPP based metalized films exhibited Non-Fickian behaviors to certain extents, with the OPET-based material showing a relatively more sever barrier breakdown at higher RH levels. The standard deviation of the test results showed a wider spread in the values for the OPET-based metalized film. The OPET-based film also showed increased deviation with the increase of the RH% levels. While the WVTR of BOPP-based metalized film showed better consistency, this structure started showing Non-Fickian behavior after 85%RH.
For more information on this study, please read the full white paper, “Non-Fickian Behaviors of Metalized Films at Higher Relative Humidity Levels” on the AMETEK MOCON website.