From breath drying to humidifying oxygen and breathing gases, Perma Pure is the partner you need to help overcome your moisture management challenges.
The Nafion™ polymer is a copolymer of tetrafluoroethylene (Teflon®) and perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid. Like Teflon®, Nafion™ polymer is highly resistant to chemical attack, but the presence of it is exposed sulfonic acid groups confers unusual properties. Sulfonic acid has a very high water-of-hydration, absorbing 13 molecules of water for every sulfonic acid group in the polymer; consequently, Nafion™ tubing absorbs 22% by weight of water.
The Nafion™ polymer transfers water molecules from one side of the membrane to the other by a first order kinetic reaction. This is unlike a porous membrane that depends on the physical size of molecules. The Nafion™ polymer selectively transfers water vapors, leaving most analytes in the gas stream untouched.
The driving force for the Nafion™ polymer to transfer water molecules is the difference in humidity levels on either side of its membrane. The Nafion™ polymer tries to attain equilibrium of the partial pressure of water vapor on either side of its membrane.
Nafion™ tubing is very stable at high temperatures. As noted previously, its chemical resistance is similar to Teflon®, and very few things can attack it. Even samples containing high concentrations of very corrosive gases like hydrogen fluoride or hydrogen chloride can be dried or processed.
In addition to the Nafion™ tubing, most Perma Pure dryers and humidifiers include a shell to contain the purge gas as well as fittings for gas connections to the gas stream and purge lines. Shells and fittings are available in stainless steel, fluorocarbon polymer, or polypropylene. For higher gas stream flow rates, bundles of Nafion™ tubing are formed using chemically resistant thermosetting epoxy resin. The temperature resistance properties of the dryers are dependent on these other materials as well. The gas stream does not come into contact with the shell but the fittings for gas stream connection do contact the gases.
Nafion™ tubing is an energy free source to transfer humidity from gas samples. When trying to add humidity to a gas stream using a liquid water source, heat energy may be required to obtain high levels of humidity transfer. The reason for this is that water needs energy to transfer from liquid phase to vapor phase. Heat will not be needed if the source is a highly humid gas environment.
Perma Pure has conducted tests to ensure the Nafion™ polymer is suitable for medical grade use. Nafion™ tubing has been tested for biocompatibility in both humidification and drying applications. It also shows an ability to fend off microbial growth. Our testing indicates that when Nafion™ tubing is placed on an agar plate, it creates a zone of inhibition around itself where microorganisms will not grow.