Humidity sensor using epoxy resin containing quaternary ammonium salts

Humidity-sensitive epoxy monomer, glycidyl trimethyl ammonium chloride (GTM AC) was selected as the humidity-sensing resin. Polypropylene glycol diglyc idyl ether (PPGDGE) and methyl tetrahydrophthalic anhydride (MTPHA) were us ed as a comonomer and a curing agent, respectively. The humidity-sensitive membranes were composed of GTMAC, PPGDGE and MTPHA. When impedance characte ristics of the epoxy resins containing quaternary ammonium salts were measu red, the impedance decreased linearly with an increase in the content of GT MAC in its semi-logarithmic graph. The impedance changed from 10(7) to 10(3 ) Omega between 30 and 90%RH, which was required for a common humidity sens or, Temperature dependence, frequency dependence and response time were als o measured. The humidity-sensitive characteristics of the sensor did not ch ange even after soaking in water. (C) 2001 Elsevier Science B.V. All rights reserved.