Investigation On Dielectric And Mechanical Properties Of Modifisied MWCNTs/PVDF Composites

With the fast development of science and technology,the development of electronics industry is particularly rapid.Carbon nanotubes as conductive filler and dielectric film modifier can improve the dielectric constant,but the interface caused by the flaws,has a great impact on the dielectric constant and mechanical properties.In this paper,two surface modification methods were used to modify carbon nanotubes,and then the influence of the two surface modification methods on the structure,dielectric and mechanical properties of PVDF-based films,has been studied.The main contents and results of the study are as follows:Firstly,MWCNTs were pickled with concentrated acid to produce more active points on their surface,then P-MWCNTs with PVDF on the surface were prepared by grafting PVDF onto MWCNTs using BPO as initiator.At last,with the modified P-MWCNTs,P-MWCNTs/PVDF composites were prepared by solution casting method.DSC,FTIR,SEM and XRD analysis showed that PVDF was successfully grafted on the surface of p-MWCNTs;and compared with unmodified and acidified MWCNTs,P-MWCNTs dispersed more homogenously in the composite films,and fewer flaws were observed,more polar phases were formed.Dielectric tests showed that the dielectric constant and the dielectric loss increases with the content of the additive.When the content of P-MWCNTs was 3 wt.%,the breakdown strength of the composite film still maintained 60.31 MV/m.The mechanical properties of the composite films are reduced with the filler content.However,compared with MWCNTs/PVDF composite films and S-MWCNTs/PVDF composite films,the mechanical properties of P-MWCNTs/PVDF composite films are significantly improved.Secondly,K-MWCNTs were prepared with KH550 as modifier,and the analysis results of FTIR,TEM and TG etc.verified that the KH550 layer was formed on the surface of MWCNTs.K-MWCNTs/PVDF composites were prepared by solution method.DSC,FTIR,XRD and other analysis methods showed that within the effective addition range of K-MWCNTs,multiply phases existedin the composite films.K-MWCNTs can induce nucleation.When the content of K-MWCNTs is 1 wt.%,the dispersion of K-MWCNTs in the matrix is good.When the content of K-MWCNTs is 3 wt.%,K-MWCNTs appear agglomeration in the matrix.The dielectric constant of the composite films is up to about 130,and the dielectric loss increases to several thousands.Percolation threshold of the K-MWCNTs was about 0.5?1 wt.%.At the percolation threshold,the breakdown strength of the composite film decreased nearly zero.Meanwhile,mechanical properties of the films also decreased with fillers,but compared with that unmodified,KH550 modification can improve the interface of the composite films and benefit to the mechanical properties.