while the diffusion coefficient Dw did not change considerably (only
22% higher).
The b value of all formulations increased as the DRH range
moved from 2–33% to 64–92%. Fig. 3 shows that for water activities
lower than 0.10 the b value was very influenced by aw, i.e.,
b decreased very quickly with the aw increase. From aw values
between 0.10 and 0.60, b was practically constant, but became very
responsive to aw when aw> 0.60.
Film densities decreased from 2.41 to approximately
1.3103 g/m3 due to cellulose fibers addition, which influenced
the values of Kw, accordingly to Eq. (5).
The DRH range did not affect a lot the Dw values of films without
fibers, indicating that in this case the Kw increasing was consequence
of the increment of b. The WF-film’ permeability was 4.5
times higher at the DRH ¼ 64–90% than at DRH ¼2–33%, due to the
big increase of b (about 6 times), while Dw did not change
considerably.
The values of Dw for P10, P30 and P50 did not present appreciable
change, except at intermediate DRH range (33–64%). For P30
samples, when DRH passed from 2–33% to 33–64%, the Kw
increased 5.6 times, due to the simultaneously increase of
b (2 times) and Dw (2.8 times). Under these DRH conditions, both
coefficients b and Dw had about the same influence on the Kw
values.
For the DRH ranges of 2–33% and 64–90% the addition of
cellulose fibers provoked decreasing of Kw from approximately 10