Oxygen permeation through Teflon–PFA tubing into flowing helium

Abstract

SYNOPSISThe permeability coefficient for oxygen diffusing through a sample of Teflon-PFA tubing has been determined experimentally. The source of the diffusing oxygen was ambient air surrounding a 1.835 m length of PFA tubing. Pressurized high purity helium was directed through the center of the PFA tubing. Oxygen permeating from the low pressure ambient air source, through the PFA tubing, and into the flowing pressurized helium was observed in the effluent gases as they passed through a trace oxygen analyzer. By this means, oxygen concentrations in the effluent helium were determined as a function of varying helium flow rates, at helium gas pressures of 1.92 and 4.40 atm (absolute), within the tubing bore. All measurements were carried out at ambient temperatures of 23.5 5 1.3"C. In addition, a theoretically related graphical method of evaluating the experimental data was employed to actually determine the oxygen permeability coefficient for this system.

Improved Synthesis of Carbon-Clad Silica Stationary Phases

“…As mentioned above, we expect that polar sites are formed due to the leakage of O 2 into the reactor − along with the formation of free radicals due to crushing silica by the rocking action of the reactor . Previous reports have shown that hot H 2 gas is capable of reducing oxidized carbon surfaces .…”

Gas permeation resistance of various grades of perfluoroalkoxy–polytetrafluoroethylene copolymers

“…(6)] and then plotted in Figure 4 as V B/AÁDp versus t according to eq. (7). The points are experimental data and the solid line represents linear regression from longer times.…”

“…A great deal is known about the purity, mechanical, and thermal properties of PTFE and its copolymers, [3][4][5] but less information is available regarding their permeation characteristics. Although some permeation studies have been performed, [6][7][8][9][10][11][12][13] many have focused on fluoropolymers for membrane applications. [11][12][13] Because PFA is a semicrystalline polymer, its properties can be strongly affected by the processing conditions.…”

Hydrogen Chloride and Ammonia Permeation Resistance of Tetrafluoroethylene−Perfluoroalkoxy Copolymers

“…Among the melt-processable fluoropolymers, tetrafluoroethylene−perfluoroalkoxy copolymers, often abbreviated simply as PFA, have the highest service temperature and therefore have been used broadly in semiconductor fabrication. , While much is known about the purity, mechanical, and thermal properties of polytetrafluoroethylene (PTFE) and its copolymers, − less information is available regarding their permeation characteristics. Some permeation testing has been performed on PFA, − but these studies have not addressed two of the most widely used process chemicals, hydrochloric acid and ammonium hydroxide. Since the active ingredient in both of these aqueous chemicals is a dissolved gas, there have been concerns about unwanted permeation potentially causing cross-contamination or corrosion.…”