2.3.2.2. Water vapor transmission rate (WVTR). WVTR
(g m2 d1) through films was determined gravimetrically
using the pouch method according to ASTM E96-95. Pouches
were placed in an environment of controlled humidity and
temperature (90% RH and 35 8C). All tests were conducted in
triplicate. The slope of the curve representing the weight
increase of the pouches versus time at the steady state of
transfer was obtained by linear regression.