Design And Preparation Of New Type Of Humidity Sensitive Composite Material

The environment humidity is closely related to the production and living of people. As a simple component to monitor the environment humidity, humidity sensors have been widely used in industry, agriculture, medical treatment, meteorology, electronics, aerospace and other fields. Many efforts have been made in the development of humidity sensitive material which is the core of the humidity sensors. Polymers have gained more and more attentions with the characteristics of wide detection range of relative humidity, fast response, easy preparation and low cost. Preparation of composite materials has been proved to be an important way to effectively improve the performance of sensitive material and has important practical significance on the research of new sensitive materials. Two types of composite have been prepared by different methods in this thesis, which are LDH-PANI/SDS inorganic-organic composite material and the CMC/PEO-TEOS composite nanofibers material.1. Conductive polymer intercalated LDHs humidity sensitive material: polyaniline (PANI) and sodium dodecanesulfonate (SDS) co-intercalated layered double hydroxides (LDH/PANI/SDS) have been obtained by coprecipitation method. The composites have been named as LiAl-LDH/PANI/SDS, MgAl-LDH/PANI/SDS, NiAl-LDH/PANI/SDS according to the composition of LDH nanosheets. All the composites have been conducted humidity sensing experiments by being fabricated into humidity sensors. It has found that the humidity sensors based on LDH/PANI/SDS behaves good humidity properties with a good linearity, little hysteresis, good stability and rapid response. Particularly, the response time of LiAl-LDH/PANI/SDS is about 2 s, the response time of MgAl-LDH/PANI/SDS is 3 s, and the response time of NiAl-LDH/PANI/SDS is about 4 s. The LDHs nanosheets play an important role in improving long-term stability and humidity sensitive properties by providing a stable environment for polymer and combining the metal cations on the LDHs nanosheets to improve the humidity response speed with polarize water molecule in the air.2. Composite nanofibers based on carboxymethyl cellulose slat: different proportions of CMC-Na/PEO-TEOS and CMC-Li/PEO-TEOS precursor solutions have been prepared at first. Fibers with an average fiber diameter smaller than 1?m have been obtained using electrospinning method under certain experimental conditions. The characterization and humidity sensing performance test indicate that 1CMC-Na/PEO-TEOSand 1 CMC-Li/PEO-TEOS exhibit good humidity sensitive properties with high sensitivity, good linearity, hysteresis, good stability.