• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.461-466
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• 1999

The humidity sensor containing ammonium salt was prepared from the copolymer of 2-methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide (MDHAB)/MMA/DAEMA = 6/3/1. The humid membrane was fabricated on the gold/alumina electrode by dipping. The impedances were $298k{\Omega},\;11k{\Omega}$, and $2.3k{\Omega}$ at 40%RH, 70%RH and 90%RH, respectively, at $5^{\circ}C$ and the humidity-sensitive characteristics were suitable for low temperature humidity sensor. The temperature-dependent coefficient between $5^{\circ}C$ and $20^{\circ}C$ was found to be $-0.80%RH/^{\circ}C$ and the hysteresis falled in the ${\pm}2%RH$ range. The response time was found to be 38 sec for the relative humidity ranging from 34%RH to 88%RH at $20^{\circ}C$. The reliabilities such as temperature cycle, humidity cycle, high temperature and humidity resistance, electrical load stability, stability of long-term storage and water durability were measured and evaluated for the application as a humidity sensor.

• Polymer(Korea)
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• v.31 no.3
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• pp.255-262
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• 2007

In this work, two types of copolymers are manufactured by a radical polymerization to develop a material for humid membrane. Each copolymer contains three monomers that have functions to improve humid-resistance, membrane stability, flexibility, impedance, and adhesion to the electrode. MDBAB (N,N'-dimethyl-2-methacryloxyethyl-3-bromopropyl ammonium bromide) having a salt form decreases the impedance of the humid membrane and reacts with amines to produce a cross-linking structure. HEMA (2-hydroxyethyl methacrylate) has an important role which reduces the impedance and increases the adhesion strength to the electrode. The other monomers are DAEMA (N,N'-dimethylamino ethyl methacrylate), 4-VP(4-vinyl pyridine), and 2-EHA(2-ethylhexyl acrylate) and all the monomers are formulated with several compositions to make a humid membrane. At specific composition, we could attain a satisfactory results having good performance and long term durability.