Abstract:

Several resistivetype humidity sensors were prepared from copolymer of \[2(methacryloyloxy)ethyl\]dimethyl butyl ammonium bromide(MEBA) and γ-methacryloxypropyl trimethoxy silane(KH570) and used as humiditysensitive material, which were respectively doped with inorganic salt LiCl, CaCl2 or FeCl3. The effects of concentrations of polymer， type of doped inorganic salt, doping concentration of salt on humidity sensitive properties of the humidity sensors were examined. The experimental results show that these humidity sensors exhibited high sensitivities(b=-0.043 8~-0.038 8) and good linearities(R=-0.994 8~-0.981 6) in a humidity range of 33%~95％RH. Increasing the concentration of polymer resulted in impedance, decrease but slower response. In addition, doping LiCl and CaCl2 caused the impedance decreases, while FeCl3 doping exhibited a different behavior. At an optimal doping concentration (1×10-2 mol/L) of LiCl, the sensor exhibits the best sensitivity(b=-0.044 6) and the shortest desorption time(20 s).

Key words: MEBA-co-KH570 copolymer, humidity sensor, inorganic salts, impedance