2.3. Membrane fabrication
2.3.1. Fabrication of Elvaloy4170 polymer membrane
In this study, Elvaloy4170 flat sheet membranes were fabricated using solution-casting method. At first, polymer Elvaloy4170 was dried under vacuum at 60 °C overnight to remove any adsorbed water. To achieve a homogeneous solution, a predetermined amount of the dried polymer was added gradually to a specified volume of toluene and the mixture was continuously stirred and heated at 50 °C for 1 day to ensure complete dissolution of the polymer. The polymer solution had a composition of 15 wt.% Elvaloy4170 and 85 wt.% toluene. Before casting, the prepared viscous polymer solution was degassed under vacuum for 12 h to remove any gas bubbles that may exist in the dope. The dope was cast onto a clear, flat and smooth Teflon plate using a casting knife with a gap setting of 300 μm at ambient temperature. Teflon plate was used in order to peel off the membrane films easily. The whole plate was covered immediately with a glass hood to allow the solvent to slowly evaporate for two days at room temperature, providing a film with a uniform thickness without curling. Once dry, the membranes were placed in a vacuum oven at 60 °C for 12 h to remove the residual solvent. Finally, the membranes were allowed to cool to room temperature under vacuum for 6 h. After the drying procedure, all membranes were cut into circles of 5 cm diameter to be used for gas permeation test.