Characterization of water structure in cellulose acetate membranes by calorimetric measurements



The heat capacities of homogeneous and asymmetric cellulose acetate membranes have been measured at different water contents within the temperature range of −40 to +20°C. The experimental heat capacity–temperature curves were verified by DTA measurements within a temperature range of −120 to +20°C. The results for the partial heat capacity of water within the membranes as well as for the heat of fusion were interpreted by assuming two different states of water—unfreezing bound water due to a sorption process and unbound water due to capillary phenomena, which freezes with a freezing point depression and a reduced heat of fusion.