The Research Of Capacitive Humidity-sensitive Properties Of FLUPI

Polymer capacitive humidity-sensitive material has become the promising material for making humidity-sensitive sensors.As one kind of the capacitive humidity-sensitive materials PI has disadvantages of a negative temperature coefficient and a protrude output,PI materials have higher hygroscopic property is the main reason.In order to reduce its hygroscopic property, minish the lag in phase of humidity, ameliorate output and minish negative temperature coefficient, the author presents the consideration of making polyimide modified, and the final intention is to make mew style fluorinated polyimides, develop humidity-sensitive sensors with good humidity sensitivity and give the base for the research of humidity-sensitive sensors.This author has obtained 2, 2'- dimido 4, 4'- nitryl diphenyl aether through nitration, selectivity reducing reaction etc. five-step method and has done many researches about the reaction. And then obtained one of fluorinated polyimide family with phenyl through two-step method and has done many research about the reaction,the conditions of this reaction. After having made sensors with fluorinated polyimide, he tested the main humidity properties of fluorinated polyimides and the influence of many factors to fluorinated polyimide sensors. By testing,it is excited to find that the fluorinated polyimide have superior humidity properties to PI. The testing result reveals that fluorinated polyimide sensors have such excellent properties with response time of 4.36S,sensitivity of 0.5550PF/%RH,humidity-sensitive hysteresis of 1.81%RH,a negative temperature coefficient of -0.1351%RH/℃and a litter protrude output. Furthermore, the paper also presents the making process,humidity-sensitive mechanism and the osmosis of moisture to polymer.