Humidity sensing properties of pre-irradiation grafting ETFE films

Acrylic acid (AA) and sodium methallyl sulfonate (SMS) have been grafted onto Poly (ethylene-co-tetrafluoroethylene) (ETFE) films by pre-irradiation, and a humidity sensing film including strong acid (-SO3Na) and weak acid (-COOH) groups has been prepared. The structure and surface morphology of both grafted and ungrafted ETFE films were observed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), respectively. a resistive humidity sensor was prepared based on the humidity sensing film and its electrical response to humidity was examined. The films showed high sensitivity with nearly three orders of magnitude change in the resistance during the relative humidity variation from 5% to 98%. The film exhibits small hysteresis (less than 2% RH) and quick response (absorption: less than 2 min; desorption: less than 4 min). The effect of grafting yield on humidity sensing properties was discussed. (authors)