The water vapor permeability (WVP) (g/Pa day m) and the water vapor transmission rate (WVTR) (g/m2 day) were evaluated following the ASTM E96-00 standard procedure. For that, equilibrated test cups containing a desiccant (15 g of anhydrous CaCl2 (Sigma-Aldrich, MO, USA), previously dried at 105 °C) were sealed with the biocomposite films. Then, the cups were put in a container at 23 ± 2 °C and 50 ± 5% RH, the weight differences being checked every 2 h for 48 h. The slope of a linear regression of the weight increase versus time was used to determine the gradient [15 (link)]. The WVTR and WVP were calculated using Equations (2) and (3):
where ∆m is the weight change of the test cups (g), T is the test time (h), and A is the test area (m2).
where p is the water vapor pressure at 23 °C (Pa), RH1 is the RH of the container (50%), RH2 is the RH inside the cups (0%), and e is the thickness (m) of the biocomposite films.
where ∆m is the weight change of the test cups (g), T is the test time (h), and A is the test area (m2).
where p is the water vapor pressure at 23 °C (Pa), RH1 is the RH of the container (50%), RH2 is the RH inside the cups (0%), and e is the thickness (m) of the biocomposite films.
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