2.3.4. Water vapor permeability (Kw)
Film water vapor permeabilities (Kw) were determined in
appropriate diffusion cells (Saranto´ poulos et al., 2002), using
a relative humidity gradient of 2–75%. Water vapor permeability
was determined using Eq. (3).
where d is the average film thickness, S is the film permeation area
(0.005 m2), aw1 (75%) is the water activity in the chamber, aw2 (2%)
is the water activity inside the cell, ps is the water vapor pressure at
the experimental system temperature (25 C) and W ¼ G/t (g of
water/hour) was calculated using the linear regression of mass
variation over time, under steady state permeation condition.