Effect of Test Conditions and Pet Surface Treatment on Moisture Barrier of Multilayer Metallized Film Structures

Abstract

Water vapor transmission rate (WVTR) testing on multilayer packaging films containing aluminum metallized polyester showed that barriers can be adversely affected by exposures to high levels of humidity. While it is a common industry practice to test and report results at 90% RH and 38 C, more realistic test conditions provide a more accurate prediction of barrier performance. WVTR results varied with the substrate surfaces beneath the aluminum metal coatings and were also dependent on which sample surface was exposed to the moist test gas. Modern test equipment and standard test methods permit testing conditions that more closely resemble the end-use conditions.