2.5.2. Water Vapor Transmission (WVP) Results

*WVP* was determined using the standard gravimetric method of ASTM E96-05. The films were covered on top of a 50 mL centrifuge tube with 20 mL of water and stored in a desiccator. *WVP* was analyzed according to the centrifuge tube weight every 12 h for 5 days and calculated with the following formula:

$$WVP = \frac{\Delta m \times d}{S \times \Delta P \times t} \tag{2}$$

where *d* is the average thickness (mm); *S* is the effective permeation area of the film (m2); Δ*m* is the mass of water permeation (g); *t* is the interval time(s); and Δ*P* is the pressure difference between the 2 sides of the film (3179 Pa).
