| Nylon-11 homogeneous membrane is employed in the original design for removal of noncondensable gases (NCGs) or air in cooling system on board spacecraft. Because the membranes are not replicable, the cost is high. In this work, deposition of a hydrophilic polymer on the lumen of a porous polyethylene (PE) tube has been developed for replacements. The PE tube substrate provides excellent chemical stability and mechanical strength, while due to elevated bubble pressure, the hydrophilic layer provides for improved retention of gas bubbles.; Studies have shown that intimate contact between the deposited layer and the substrate is required to overcome surface energy differences that reduce good adhesion. This has been accomplished by presoaking the PE tube in the solvent to raise its average surface energy and by applying a pressure difference between the lumen and the outside of the PE tube during processing. Polymer solutions of different concentrations have been used to promote the penetration and control membrane surface layer thickness. Air-flow of various flow rates through the tube during drain time was employed to improve the performance of composite membrane. The resulting composite membranes have shown repeatable decrease in water permeability, which is indicative of a decrease in membrane pore size. Swelling of the added separation layer was observed, which causes a slight decrease in membrane pore size, and should result in improved bubble retention. PES/PSf blends experiment suggested that the hydrophilicity of polymers used as separation layer had significant effect on water permeability of the composite membrane.; A series of gas slug injection tests were conducted to determine the capability of the composite membranes to remove slugs of gas in flowing systems. Results have been promising with negligible gas permeation for the composite membranes compared to 100% gas permeation in the blank PE tube.; Drain tank model, mass transfer model, and mathematical model were used to calculate casting film thickness, membrane thickness, and depth of penetration, respectively. The comparisons of the outputs of these models with experimental data showed that these models work very well in this research. |
