Study On The Impact Of The Interfacial Polarization On Dielectric Properties Of Carbon Nanotubes Elastomer Composites

Dielectric elastomer is a new type of electroactive polymer.That material being deformable in loading can cause the electric field change of materials,so they are widely used in the sensors.However,the low dielectric constant of elastomer limits their applications.As a resultresearchers have been working to develop dielectric film with outstanding dielectric performance and lower dielectricloss.Doping nano-fillers in the elastomer material,especially the conductive filler is a very effective method.According to the theory of percolation threshold,near the percolation threshold of conductive fillers content,the material can show superior dielectric properties.Dielectric behavior of the material is mainly due to the polarization effect in the material.As far as the dielectric composite material is concerned with the conductive nano-fillers,interfacial polarization plays a leading role.In the previous studies,major efforts were made in researching different kinds of modified fillers,or the use of special compound method to enhance the interfacial polarization.Limited by microscopic characterization method of interfacial polarization,there are little studies on how interface at the micro level effect interfacial polarization.So this paper studies the two different modification methods in order to make clear the influence of the modified fillers on interfacial polarization respectively.(1)Different amount of silane coupling agent KH570 was used to modify carbon nanotubes to prepare modified carbon nanotubes.A series of Nanotube/hydrogenated butyronitrile dielectric elastomer composites were prepared by solution method..The change of interface layer thickness was characterized by AFM.The circuit fitting method was used to characterize the interface polarization effect,and the relationship between interface structure,interface polarization and dielectric properties was studied.The experimental results show that the increase of the grafting ratio of carbon nanotubes will increase the interfacial force between the filler and the rubber matrix,so the thickness of the interfacial layer will increase.The thickness of the interfacial layer increases from 4.5 nm to 5.3 nm and the lamellar thickness increases from 12.7 nm to 20.7 nm.The volume fraction of carbon nanotubes is 1.5vol.%The dielectric constant of composite increases with the grafting rate from 12.3 to 18.2,and the dielectric loss increases.According to the fitting data of the circuit,the interfacial polarization also increased substantially.Therefore,the polarization of the interface of the material is the result of the combined effect of the loose layer of the close layer in the interface layer.(2)Carbon nanotubes are coated with dopamine and the thickness of coating layer is controlled.Two modified methods could affect the interfacial polarization of dielectric elastomers.Finally the experimental results show that by changing the grafted rate of coupling agent on carbon nanotubes,interface polarization of hydrogenated nitrile/carbon nanotube composite material is different.Therefore,the dielectric constant of the composite can be improved.Carbon nanotubes being coated insulating layer at the surface can significantly reduce the intensity of interfacial polarization and dielectric properties of materials will also be significantly reduced.