Author(s): Cenita Rodehed, Bengt Rnby
A saponified starch-polyacrylonitrile graft copolymer containing water was studied using differential scanning calorimetry. The samples had a moisture content in the range of 0-1.05g water per gram of dry polymer. Molar heat capacity measurements at temperatures higher than 273 K gave partial molar values between those of ice and bulk liquid water. No crystallizable water was detected in samples with water contents lower than 0.44 g/g dry polymer. In samples containing larger amounts of water, both the amount of “bound” uncrystallizable water and the amount of “free” crystallizable water increased linearly. Two melting endotherms were detected, suggesting that the free water could be divided into two components withdifferent melting points (268 K and 274 K, respectively).