DENSE POLYMER FILM AND MEMBRANE FORMATION VIA THE DRY-CAST PROCESS .2. MODEL VALIDATION AND MORPHOLOGICAL-STUDIES

In order to validate the dry-cast model developed by us, a multifacete d experimental approach was undertaken whereby three process variables can be followed independently in real time. Since it is extremely dif ficult to determine experimentally the concentration and temperature p rofiles within the cast polymer solution, experiments were designed so as to provide information on the coupled mass- and heat-transfer proc esses by measuring other process variables. The experimental data-acqu isition technique combined gravimetric, inframetric, and light-reflect ion analyses which provided information on the overall mass change, su rface temperature, and the onset and duration of phase separation, res pectively. Structural studies were conducted using scanning electron m icroscopy. These studies revealed that macrovoids or ''fingers'' can b e formed in dry-cast members. A hypothesis for the formation of finger s based on the model predictions and experimental observations is prop osed.