2.7. Film solubility in water
The film moisture equilibrium content at 58% RH was determined
gravimetrically by desiccating the conditioned films at
105 C for 24 h. Three film specimens measuring 4 cm2 were
weighed accurately and placed in beakers with 25 mL of distilled
water and then sealed and gently shaken at 25 C for 24 h. The
solution was then filtered through Whatman No. 1 filter paper to
recover the remaining undissolved film, which was desiccated at
105 C for 24 h. Film solubility was calculated by the equation:
FS ð%Þ ¼
Wo Wf
Wo
*100 (2)
where Wo was the initial weight of the film as dry matter and Wf
was the weight of the undissolved desiccated film residue. All tests
were carried out in quadruplicate.