Preparation And Properties Of Epoxy Resin/Nickel Coated Carbon Fibers Conductive Composite Foams

Polymer-based conductive composite foams are widely used in packaging,sensor and electromagnetic shielding due to their excellent performance.As one of the most widely used thermosetting resins,epoxy resin(EP)has excellent mechanical,thermal stability and chemical resistance.Therefore,it is of great significance to prepare high performance and multi-functional EP conductive foams.In this paper,nickel-coated carbon fiber(NCCF)with large aspect ratio and high conductivity was prepared by electroless plating.EP/NCCFs conductive foams were prepared by compression molding and chemical foaming.On the basis of this,a small amount of carbon-based filler(carbon black(ACET)and carbon tube(CNT))were doped into EP/NCCFs conductive foam,The effects of these two fillers on the properties of conductive foams were studied.We also use the nano ferroferric oxide partly replace ACET in the EP/NCCFs/ACETs system,and obtain the EP/NCCFs/ACETs conductive foams doped with magnetic particles.(1)The nickel coated carbon fiber(NCCF)with core-shell structure was successfully prepared by electroless plating.The conductivity of NCCF could be as high as 167 S·cm-1.A light-weight and electromagnetic interference(EMI)shielding conductive epoxy resin(EP)composite foam was fistly fabricated by loading NCCFs.The foamed EP/NCCFs composites with a uniform foam cell containing various NCCF contents(0-5.03 vol%)have been fabricated via chemical foaming.The foams exhibit densities of as low as 0.45 g cm-3.Owning to the high aspect ratio of carbon fiers and selective distribution of NCCF in the foam structure,NCCF could easily connect with each other and construct the conductive network in polymer matrix.As a result,the composite foams exhibit an EMI shielding effctiveness(SE)of ~33 dB and a corresponding specifi EMI SE of as high as 77.4 dB cm3 g-1 in the microwavefrequency range of 8.2–12.4 GHz.(2)On the basis of EP/NCCFs conductive foams,the lighter conductive foams were prepared in the same approach by doping a small amount of acetylene black(ACET)and carbon nanotube(CNT)using a combinatorial technology of mould pressing and chemical foaming.Owning to the high aspect ratio of NCCF and the synergistic effect of conductive fillers with different dimensions in the foam structure,NCCF and the second conductive filler(ACET or CNT)could easily connect with each other and construct the conductive network in polymer matrix.The density of the two foams can be as low as 0.18 g cm-3.Through the doping of ACET and CNT,the cell size of the EP/NCCFs foam is reduced and the cell density is increased.Also it can effectively reduce the percolation and significantly improve the conductivity and EMI performance.After the doping,these two composite foams show a ultra low percolation threshold of 0.60 and 0.41 vol%,respectively.The EP/NCCFs/CNTs foams presents high performance EMI shielding with a remarkable effectiveness and a corresponding average specific EMI SE of ~41 dB and ~227 dB cm3 g-1,respectively,which is twice that of EP/NCCFs/ACETs composite foam.(3)Based on the EP/NCCFs/ACETs conductive foams,ACET was partly replaced by the magnetic nano ferroferric oxide.After the nano ferroferric oxide doping,the cell size is reduced and the cell density is increased.Although the conductivity of the foams decrease with the increase of the doping content,the EMI and mechanical properties of the foams increase due to the magnetic and rigidity of the ferroferric oxide.