Water vapor permeability (WVP) of chitosan films
ASTM E96 (ASTM, 2000) standard for testing WVP was adopted. The samples of chitosan film with a 6 cm diameter were prepared. Next, sealant was directed around testing cups containing distilled water. Then, the testing cups were covered with the samples. The cups were closed and knotted with the lids. They were weighted carefully and put in the chamber. The changing weight was recorded every one hour until the weight was 1% different. The following formula was used in calculating the water vapor permeability rate.