2.4. Hydrolysis
The film samples prepared by compression molding were cut into 1 3 cm2 specimens for hydrolysis study. Each pre-weighed specimen (W0) was dipped in a vial containing 10 mL deionized water and the vials were placed in a water bath at a constant temperature of 58 C. Three specimens of each sample were picked out at predetermined time, washed with deionized water, dried to a constant weight in vacuum oven at 40 C and weighed again (Wt). The mass loss was calculated from the following formula: mass loss(%) ¼ (1Wt/W0) 100, and all the values presented were the average of three specimens.