Extensive research is being carried out worldwide to develop more efficient, more compact, more powerful, and more cost-effective batteries and fuel cells. Innovative components being devised need to be evaluated for their liquid permeability in order to assess their suitability. Permeability for gaseous reaction components is also important for assessment of reaction rates and performance of the device. Batteries and fuel cells often use very strong liquid chemicals. High operating pressures and temperatures above room temperature are also encountered. One goal of fuel cell designers is to raise the temperature of operation in order to increase the efficiency of the electrochemical processes that occur in the system. It is, therefore, important to evaluate permeability under simulated service conditions of chemical environment, pressure, and temperature rather than extrapolate results obtained under laboratory conditions, which can be considerably different.

Equipment has been designed and permeability has been measured in strong chemical environments, elevated temperatures, and high pressures. The results show interesting possibilities.

Technique

Liquid from a tube of known volume is forced through the sample. The pressure on the liquid and the volume of the liquid forced out of the tube are measured. Alternatively, the liquid is pressurized to force it through the sample and the volume of liquid coming out of the sample is measured. Liquid permeability is computed from the pressure on the liquid, the volume of liquid passing through the sample, and the sample dimensions.

For determination of gas permeability, pressure and flow rates of a gas are measured as it passes through the sample.