Study On High Dielectric Constant Resin Composites Based On Three-dimensional Conductive Framework Structure And Multilayer Structure Interface Polarization

High dielectric constant materials play an important role in the development of modern industry due to their ability to store electrical energy and uniform electric field,while high dielectric constant composites have low dielectric loss,good processability and low cost.Among them,the conductor/polymer matrix composite can obtain high dielectric constant at a low content of the filler,but the high dielectric loss and low dielectric constant caused by the agglomeration of the conductor are widely used.Therefore,this paper studies the high dielectric constant with lower filler addition amount,high dielectric constant and low dielectric loss obtained at same filler addition,which mainly includes the following two parts:Firstly,fPCNT/EP composites were prepared by using CNT as conductor and PVDF as binder to prepare fPCNT framework with three-dimensional network structure and then infiltrating EP resin.The dielectric properties were tested and compared with the dielectric properties of CNT/EP and CNT/PVDF/EP composites.The effects of three-dimensional structure on percolation thresholds and dielectric properties of composites were investigated.The results show that the percolation thresholds(fc)of CNT/EP,CNT/PVDF/EP and fPCNT/EP composites are 0.34wt%,0.38wt%and 0.25wt%,respectively,indicating that the three-dimensional network structure helps to reduce the fc of composite.In addition,the fPCNT/EP composite has a higher dielectric constant than CNT/EP and CNT/PVDF/EP.When the CNT content is 0.28 wt%,the dielectric constants of CNT/EP and CNT/PVDF/EP are respectively 55 and 50 at 100 Hz.When f is 0.25 wt%,the dielectric constant of fPCNT/EP can reach 170,and the dielectric loss is 0.5 at 100 Hz,which satisfies the requirements for practical use.In addition,compared with M20-CNT/EP,M450-CNT/EP,CNa-CNT/EP and CC-CNT/EP composites,the fPCNT/EP composite has a higher dielectric constant and better dielectric constant-frequency stability at the same CNT content.It is found that the increase of the dielectric constant of fPCNT/EP composites is mainly due to the microscopic interface between fPCNT and EP,which causes interface polarization and achieves the purpose of increasing dielectric constant.Secondly,multilayer composites were prepared by using PP and TiO2 nanorod array films as insulating layers.The influence of the layers on the composites and their placement were studied.When the amount of CNT added is 0.4wt%,the dielectric constant of the CNT/EP composite is about 95 at 100 Hz.As the insulating layer is added,the dielectric constant of the composite also increases.The insertion of single-layer and double-layer PP films can increase the dielectric constant of the composites to small extent.It is worth noting that the addition of the TiO2 nanorod array film has greatly improved the dielectric constant of the composite.Specifically,with same amount of CNT,the addition of the single-layer TiO2 nanorod array film increased the composite from about 95 to about 1750,an increase of nearly 20 times.In addition,the two-layer TiO2 nanorod array further increases the dielectric constant of the composites,and its dielectric constant is above 2000.At the same time,the dielectric constant of the multilayer composite is also related to the orientation of the two layers of TiO2 nanorod arrays,that is,the strength of the interfacial polarization.In addition,through equivalent circuit simulation and Nyquist curve study,it is found that compared with CNT/EP composites,multi-layer composites have more parallel circuits,and their Nyquist curves also have obvious double semicircular shapes,which indicates the existence of insulating layers,and bringing a macroscopic interface,causing interface polarization,resulting in an increase in dielectric constants.