| Carbon nanotubes have been recognized as one of the potential candidates for gas sensing materials due to its distinguished properties such as small diameter, remarkable absorption ability. The PMMA/PVAc composites is a compatible blends. We fabricated the carbon nanotubes/PMMA/PVAc composite film, and investigated its microstructure and electric properties and performance of applications such as vapor detectors. It would be a good candidate for gas sensing materials. The research work consists of:1. Thin films of poly(methyl methacrylate)(PMMA), poly(vinyl acetate)(PVAc) and carbon nanotube composite were produced by different dispersion and coating method. The best way to produce carbon nanotubes/PMMA/PAVc composite film with conductive network is dispersing carbon nanotubes by ultrasonic and sulotion casting.2. Carbon nanotubes content dependences of the electric resistance of the carbon nanotubes/PMMA/PAVc composite film was investigated. The volume electric resistivity of carbon nanotubes/PMMA/PVAc decreased with increasing the content of carbon nanotubes. The electrical percolation thresholds were at5wt%and2wt%respectively in the CNTs/PMMA/PVAc film and GCNTs/PMMA/PVAc film.3. Effect of structure of the carbon nanotubes on conductivity and electric resistance response of the carbon nanotubes/PMMA/PAVc composite film was investigated. The conductivity of the CNTs/PMMA/PVAc composite film is better than that of GCNTs/PMMA/PVAc composite film. But, the electric resistance response of CNTs composite film is better than GCNTs composite film.4. At a fixed vapor of THF, carbon nanotubes content dependences of the electric resistance response of the carbon nanotubes/PMMA/PAVc composite film was investigated. The maximum electric resistance response increased with increasing carbon nanotubes content, But when the content of carbon nanotube is close to3wt%, The maximum electric resistance response is0.092which is the best response. Then, with increasing carbon nanotube content, the maximum electric resistance response began to decreased.5. At different vapor concentration of THF, the electric resistance response of CNTs/PMMA/PVAc composite film was investigated. In the adsorption zones, the electric resistance increased with increasing time. But in the desorption zones, the electric resistance decreased with increasing time. And with THF concentration increasing, the electric resistance began to increase. The electric resistance response of the composite film is linear with THF concentration. 6. At different vapor concentration of ethyl acetate, the electric resistance response of CNTs/PMMA/PVAc composite film was investigated. The electric resistance response of the film is similar to the CNTs/PMMA/PVAc composite film at0.6-6ppt THF. And the electric resistance response of the composite film is linear with ethyl acetate concentration.7. At different vapor concentration of acetone, the electric resistance response of CNTs/PMMA/PVAc composite film was investigated. Comparing to same vapor concentration of THF and ethyl acetate, the electric resistance response of CNTs/PMMA/PVAc composite Film in the acetone is smaller.8. At different vapor concentration of ethanol, the electric resistance response of CNTs/PMMA/PVAc composite film was investigated. The momo-peak of electric resistance in the ethanol is smooth. And the electric resistance response began to increase with ethanol concentration increasing. But the change of electric resistance is smallest and the linearity is bad, comparing with above three kinds of vapor.9. PVAc content dependences of the electric resistance response of CNTs/PMMA/PVAc composite film was investigated. In different vapor, the electric resistance response of the film decreased with increasing the content PVAc.10. The electric resistance response of CNTs/PMMA/PVAc composite film to above four kinds of vapor is as follows:ethyl acetate>THF>acetone> ethanol. 11. At the same time, the conductivity and the electric resistance response of CB/PMMA/PVAc composite film are studied. The conductivity of CB/PMMA/PVAc film is better than that of CNTs/PMMA/PVAc composite film. When the content of CB is close to20wt%, the maximum electric resistance response is0.085, which is the best effect. But for CNTs/PMMA/PVAc composite film, when the content of CNTs is close to3wt%, the maximum electric resistance response is the best. So the electric resistance response of the CNT/PMMA/PVAc film is better than that of CB/PMMA/PVAc film. |
