Competitive sorption of water vapor and CO2 in photocrosslinked PVCA film for a capacitive-type humidity sensor
✍ Scribed by Masanobu Matsuguchi; Nozomi Maeda; Yoshiro Sakai
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 193 KB
- Volume
- 83
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
The sorption behavior of water vapor and CO 2 gas in photocrosslinked poly(vinyl cinnamate) (PVCA) film was examined at 30°C under atmospheric pressure. Both the water sorption isotherm and the CO 2 sorption isotherm obtained with quartz crystal microbalance (QCM) method obeyed the simple Langmuir's equation. Water vapor/CO 2 mixed-gas sorption isotherms were also obtained. Total amount of sorbed mixed gases was clearly influenced by the partial pressure of water vapor (p w ) and CO 2 gas (p c ) in the atmosphere. A modified Langmuir's equation based on a dual-site model was employed for predicting the competitive adsorption isotherm, and the isotherm was clearly described by the equation. The theoretically estimated amount of adsorbed water at the constant p w decreased slightly with increasing p c . The effect of this phenomenon on the sensitivity of the capacitive-type relative humidity sensor was examined. As expected, the electrical capacitance of the sensor at the constant relative humidity decreased because of the coexistence of CO 2 gas. However, the influence was quite small in the CO 2 concentration range in the ordinary environment.