Experiments were conducted on the effects of temperature, polymer molecular weight, and carbon loading on the electrical resistances of polymer/carbon-black composite films. The experiment were performed in a continuing effort to develop such films as part of the JPL Electronic Nose (ENose), that would be used to detect, identify, and quantify parts-per-million (ppm) concentration levels of airborne chemicals in the space shuttle/space station environments. The polymers used in this study were three formulations of poly(ethylene oxide) [PEO] that had molecular weights of 20 kilodaltons, 600 kilodaltons, and 1 megadalton, respectively.
The results of one set of experiments showed a correlation between the polymer molecular weight and the percolation threshold. In a second set of experiments, differences among the temperature dependences of resistance were observed for different carbon loadings; these differences could be explained by a change in the conduction mechanism.
In a third set of experiments, the responses of six different polymer/ carbon composite sensors to three analytes (water vapor, methanol, methane) were measured as a function of temperature (28 to 36°C). For a given concentration of each analyte, the response of each sensor decreased with increasing temperature, in a manner different from those of the other sensors.
This work was done by Allison Manfreda, Liana Lara, April Jewell, Margie Homer, Shiao-Pin Yen, Adam Kisor, Margaret Ryan, Hanying Zhou, Abhijit Shevade, and Lim James of Caltech and Kenneth Manatt of Santa Barbara Applied Research for NASA’s Jet Propulsion Laboratory.
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Refer to NPO-40621, volume and number of this NASA Tech Briefs issue, and the page number.