2.2 Determination of Water Vapor Transmission
Rate (WVTR)
WVTR was determined gravimetrically
according to ASTM E96-95 (ASTM, 1995). Film
specimens, approximately 8 cm diameter, were
mounted on the aluminum cups containing 10 grams
of silica gel. Paraffin was used to fix a film specimen
to the wide rim of an aluminum cup. The cups were
weighed and then placed in a desiccator containing
saturated calcium chloride solution. The relative
humidity of the chamber was kept at 35 ±2% and 25
±1°C throughout the experiment. The water vapor,
which passed through the film, was determined by
recording the weight gain daily for 5 days. The test
was performed in triplicate. WVTR was calculated
using the following equation.