A HUMIDITY SENSOR USING POLYTETRAFLUOROETHYLENE-GRAFT-QUATERNIZED-POLYVINYLPYRIDINE

On polytetrafluoroethylene films (0.05 and 0.5 mm thick), polyvinylpyridine was graft-polymerized by gamma-ray irradiation. After quaternization of the pyridyl group of the grafted films, sandwich and surface-type sensors were prepared by vacuum deposition of gold electrodes. Electrical properties of these resistive-type sensors were studied in relation to the grafting ratio as well as the amount of sorbed water. Scanning electron microscopy observations and impedance measurements suggest that for the 0.05 mm film, graft-polymerization proceeds homogeneously into the film, while for the 0.5 mm film, the reaction is limited only near the surface of the film and is inhomogeneous. The prepared sensor is completely resistant to water.