A novel gas sensor from crystalline polymer-grafted carbon black: responsibility of electric resistance of composite from crystalline polymer-grafted carbon black against solvent vapor

AbstractElectrically conductive immiscible polymer blends containing high impact polystyrene (HIPS), liquid crystalline polymer (LCP) and a low content of conductive carbon black (CB) were studied to establish and understand the correlation between composition, electrical properties and the morphology of filaments produced at different melt flow conditions. The HIPS/LCP/CB blend containing 30% LCP and at least 2 phr CB reveals a stable resisitivity throughout the shear rate range applied in a capillary rheometer. Interesting structure alterations were observed for the LCP and CB components as a result of melt flow processing. Unusual sensing properties of liquids were found for the blends containing LCP.

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Rheological Properties of Carbon Fiber and Carbon Black Filled Liquid Crystalline Polymer Melts

Applied Rheology ◽

10.1515/arh-2001-0011 ◽

2001 ◽

Vol 11 (4) ◽

pp. 188-196 ◽

Cited By ~ 8

Author(s):

Katsuhiko Araki ◽

Takeshi Kitano ◽

Berenika Hausnerova

Keyword(s):

Shear Rate ◽

Carbon Fiber ◽

Carbon Black ◽

Liquid Crystalline Polymer ◽

Liquid Crystalline ◽

Filler Content ◽

Crystalline Polymer ◽

Normal Stress Difference ◽

Steady Shear Viscosity ◽

Rate Region

Abstract The rheological properties of thermotropic liquid crystalline polymer (LCP) and its carbon fiber (CF) and carbon black (CB) filled composites in molten state were measured using a cone-plate rheometer. The measurements of the CF/LCP and CB/LCP melts were performed with carbon fiber contents of 5, 10 and 20 wt %, and carbon black contents of 1.5, 3, 5, 10 and 20 wt %. As expected, steady shear viscosity of the LCP, CF/LCP and CB/LCP melts in a low shear rate region (0.1 to 1 s-1) decreased with an increase of temperature and increased with rise of filler content. In shear rate region of 1 to 50 s-1, the LCP melt showed a unique viscosity behaviour with maximum and minimum values. The CF/LCP and CB/LCP melts showed disappearance of such a unique viscosity behaviour with an increase in the CF (CB) content and an increase of temperature. CB filler had a more pronounced effect on the disappearance of the unique viscosity behaviour in comparison with CF. Regarding apparent yield stress, the CF/LCP melts gave the same value as pure LCP, the CB/LCP melts showed an increase of yield with a rise of the filler content. In addition, the first normal stress difference of the LCP and CF/LCP melts are smaller than yield stress values, although the rate of increase with shear rate is higher in case of normal stress difference than in case of yield. The results of the dynamic shear oscillatory flow measurements of CF and CB based compounds at 300˚C showed that both, the storage and loss moduli are more affected by carbon black filler. Complex viscosity values of the LCP and CF/LCP melts showed no such unique complex flow pattern as observed in the case of steady shear viscosity.

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A NOVEL GAS SENSOR FROM POLYMER-GRAFTED CARBON BLACK: EFFECTS OF POLYMER, CRYSTALLINE ORGANIC COMPOUND, AND CARBON BLACK ON ELECTRIC RESPONSE TO TETRAHYDROFURAN VAPOR

Journal of Macromolecular Science Part A ◽

10.1081/ma-100103356 ◽

2001 ◽

Vol 38 (4) ◽

pp. 383-398 ◽

Cited By ~ 24

Author(s):

Jinhua Chen ◽

Norio Tsubokawa

Keyword(s):

Organic Compound ◽

Carbon Black ◽

Gas Sensor ◽

Electric Response

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Measurement of Solvent Vapor Absorption by Polydimethylsiloxane Using Quartz Crystal Microbalance

2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems ◽

10.1115/micronano2008-70163 ◽

2008 ◽

Cited By ~ 1

Author(s):

W. W. F. Leung ◽

C. Chao ◽

C. H. Cheng ◽

K. F. Lei ◽

D. Ngan ◽

...

Keyword(s):

Frequency Shift ◽

Gas Sensor ◽

Quartz Crystal Microbalance ◽

Quartz Crystal ◽

Specific Area ◽

Small Mass ◽

Crystal Oscillator ◽

Solvent Vapor ◽

Adsorbed Gas ◽

Micro Electromechanical System

A new micro-electromechanical system (MEMS) gas sensor has been developed using quartz crystal microbalance (QCM) with adsorbent coated in form of nanofibers on the QCM sensor. The nanofibers with fiber diameter typically around 200–300 nm increases the specific surface area to enhance adsorption. The QCM is made to oscillate at its natural resonance frequency. Upon exposure of the gas sensor to a given gas, the adsorbed gas onto the nanofibers adds a small mass which changes the natural frequency of the oscillation. By detecting the frequency shift due to adsorption of a given gas, the presence of the gas is detected, and by measuring the frequency shift, the amount of gas being adsorbed at a given pressure and temperature is quantified via the Sauerbrey equation [1]. A circuit has been developed to read the frequency shift due to the energy dissipation in the QCM coated with Polydimethylsiloxane (PDMS) nanofibers under the environment of several solvent vapors. The developed circuit includes two crystal oscillator circuits, two QCM’s which are respectively 1MHz reference QCM and a coated QCM, RC filter and AND gates. The results of the frequency shift between the reference QCM and the coated QCM were recorded on the oscilloscope so as to investigate the relationships between the frequency shift and the amount of vapor adsorbed for different gases. Ultimately, Volatile Organic Compounds (VOCs) are the target to be monitored and a MEMS based sensor will be developed similar to the present QCM gas sensor discussed herein. This work provides the feasibility study for using nanofiber coating to enhance the adsorbent specific area and a stand-alone QCM sensor for making measurement.

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