The WVP of films was determined using a gravimetric method
in accordance with the ASTM E-96-95 standard method. Water
vapor transmission rate (WVTR) ofthe film sample was determined
gravimetrically at 25 ◦C under 50% RH conditions using water
vapor permeability measuring cups as described by Gennadios,
Weller, & Gooding (1994). The WVTR (water vapor transmission
rate in g/m2 s) was calculated by the linear regression from the
linear portion of the weight change vs. time curve. Then the WVP
(g m/m2 s Pa) of the film was calculated using the following equation: