Each film was cut into 2.5×2.5 cm and weighted in air-dried conditions (w1), then immersed in deionized water (25 °C) for 2 min. Wet samples were wiped with filter paper to remove excess liquid and weighted (w2). The amount of adsorbed water was calculated as
where w2 and w1 are, respectively, the weights of the wet and the air-dried samples (Bigi, Panzavolta, & Rubini, 2004). Each type of film was repeated three times, and took the average as the results.
The weight gain of swollen films (Ws) was measuredat selected times, after gently blotting the surface with filter paper,until equilibrium was reached. The swelling ration (SR) was eval-uated using the following equation