Studies On Dielectric And Resistance-Pressure Properties Of Carbon Nanotubes/Silicone Rubber Composites

The electrical conductive rubber-based composites can be used as pressure-sensors in practice. However, in the past, the pressure-sensitive materials developed slowly due to the limitation of fillers and the preparation technology. Meantime, this kind of materials is a new type of high-dielectric constant materials. The law of polarization and the mechanism of electric conductance under the alternating current (AC) field are still uncertain, although dielectric performance and percolation effect were studied in the past years.In this paper, multi-walled carbon nanotubes(MWNT) with excellent properties are used as the functional fillers, their composites with silicone rubber(SR) were prepared by wet method and three roll mills mixing method and the electrical conductive, dielectric and resistance-pressure properties of composites were investigated.It is found that coupling agent KH550 was a kind of simple and effective modifier, which can improve the interfacial interaction, the dispersion and the mechanical properties of composites. Meanwhile, the dispersion of the modified MWNT/SR composites prepared by three roll mills is completely homogenous.The percolation effect and the factors of electrical conduction were studied. It is found that the percolation threshold of MWNT/SR composites is small and only 1.0 vol. %, which guarantees the good elasticity and stabilization of composites. Meanwhile, the relationship between dispersion and electrical conductive properties was explored and the conduction mechanism is summed up.According to the analysis of the alternating current impedance spectra, the equivalent circuits of MWNT/SR composites are built and the law of polarization and mechanism of electric conductance under the alternating current (AC) field were explored. It is founded the resistance of MWNT/SR composites increases with the applied pressure, which is different with the traditional pressure-sensitive conductive materials. The mechanism and factors of pressure-sensitive properties are investigated. It is concluded that the MWNT/SR composites have high resistance-pressure sensitivity, good controllability and stable property as force-sensitive element, which are potential to be used a novel type of pressure sensor.