Polymeric alternatives to teflon for membrane stripping

Membranes were manufactured using a novel plasma sputtering technique that rendered the surface hydrophobic. These membranes are cost effective compared to Teflon (polytetrafluoroethylene, PTFE) and allow for a greater selection of membrane alternatives. The nylon substrates used here were surface treated for 30 minutes at a power rating of 100 W to achieve an optimal surface contact angle of 151° and a surface fluorine concentration of 40%. Reductions in surface oxygen and carbon levels of the treated membranes suggested surface masking of the substrate, typical of sputtered surfaces. The breakthrough pressure of the membranes was found to be independent of the surface properties and was optimized at 200 W and 90 minutes of treatment. This suggests that penetration of the membrane pores by hydrophobic sputtered material improves the resistance to wetting. Membrane stripping experiments show that at elevated temperatures plasma sputtered nylon has increased mass transfer over a comparable PTFE membrane. Both membranes displayed signs of wetting as a result of elevated system temperature which causes a reduction of the solvent surface tension, that contributes to wetting.