Aijiren PTFE membrane filter for gasses-PTFE Membrane Filter. May 01, 2006 · The 47-mm membrane filter disks (Millipore, Bedford, MA), all having 0.45 μm pore sizes, included nylon 66, hydrophobic and hydrophilic polytetrafluoroethylene (PTFE), and mixed cellulose ester membranes. Nylon 66 filters were also purchased