A Novel Manufacturing Process to Fabricate Double-Layer Membranes

A new method to fabricate double-layer membranes by using a specially design casting machine is described in this study. This machine is able to produce membranes with a double-layer structure via a single-casting technique with the use of a closed-loop feedback control system. The membrane casting operation is controlled by a programmable logic controller (PLC). Membranes produced from this simplified technique exhibit similar properties as the double-cast membranes, such as a macrovoid free structure and good porosity property. Results show that high casting speed is desired during the membrane fabrication process as the relaxed polymer molecular orientation and low polymer chain entanglement promote vertical swelling, and hence enhance the membrane porosity. Turbulent coagulant flow further improves the membrane porosity due to the high solvent–coagulant exchange rate during the phase inversion process. In summary, this machine simplifies the double-casting technique and produces membrane with similar advantages as the membrane fabricated via a double-casting technique.