On the other hand, a PERMATRAN-W?Model 3/33 (Mocon Inc., USA) was used to measure films water vapor transmission, according to ASTM F 1249-89 standard method. Film sample was
placed in a test cell which is divided into two chambers separated by the specimen. The inner chamber is filled with nitrogen (carrier gas) and the outer chamber with water vapor (test gas).
Water molecules diffuse through the film to the inside chamber and WVTR is registered. Measurements were carried out at 25?C and films were subjected to a partial water vapor pressure
gradient. Masking specimens with precut aluminum foil were used to avoid saturation leaving an uncovered film area of only 5 cm2.