3.1.3. Water vapor permeability (WVP)
It was observed that the film WVP values increased with
increase in WPI concentration (Fig. 3). Mean values of
WVP for the 9% WPI films were much higher than 7% films
which were also higher than 5% films. Besides, it was also
observed that there was a significant difference between
WVP values of films made with 5% and 7% on one side
and 7% and 9% on another side (p < 0.05). The results
clearly showed how varying the concentration of WPI
could influence the water barrier property of the films as
studied by McHugh et al. (1994). This might be due to an
increased number of air bubbles when the concentration
became relatively high. The formation of bubbles could
probably be explained by the larger pores formed at high