Humidity sensor using microporous film of polyethylene-graft-poly-(2-hydroxy-3-methacryloxypropyl trimethyl-ammonium chloride)
An hydrophilic monomer, 2-hydroxy-3-methacryloxypropyl trimethylammonium chloride, was graft-polymerized in a microporous polyethylene film using three different initiation methods, that is, with benzyl peroxide, pre-U.V. irradiation and mutual photo-initiation. Humidity dependence of the impedance was measured for the grafted microporous polyethylene films. Among the three graft polymers, the one prepared by pre photo-irradiation seems to have the most homogeneously grafted layer. The impedance increases as the grafting percentage increases except in the low grafting percentage region. The response time for the abrupt change of humidity becomes longer as the grafting percentage increases. The activation energy for conductivity has a maximum at 40% relative humidity in the plot of activation energy against humidity.
KeywordsPolymer Peroxide Activation Energy Relative Humidity Response Time
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