What membrane has been used to prevent water vapor from passing, but would allow regular air to pass?
The common membranes used for gas/air filtration are our hydrophobic Polypropylene and PTFE Membranes. They both inhibit the flow of water vapors (hydrophilic) while allowing regular air molecules (such as oxygen) to pass.
For the PTFE membrane the water intrusion pressure (which is inversely related to pore size) is greatest with the smaller sizes:
|
Water Intrusion of PTFE |
| Pore Size (um) |
Water Intrusion Pressure (psi) |
| 0.2 |
40 |
| 0.45 |
20 |
| 1.0 |
7 |
| 3.0 |
2 |
| 5.0 |
1 |