Study On Conductive Properties Of Ethylenediamine Modified Nickel-coated Graphite/Epoxy Resin Composites

Epoxy conductive composites have excellent processing and electrical properties,and have great potential for development in coatings and packaging,adhesives,electronics,aerospace and aviation.In order to obtain low-cost,high-conductivity epoxy-based conductive composites,conductive composites were prepared using nickel-coated graphite(NCG)filled epoxy(EP).Due to the high density of NCG and its easy settlement in the polymer matrix,this article mainly explores the formula design and process conditions of NCG/EP composites,and focuses on solving the problem of settling of NCG in EP matrix and further improving the electrical conductivity of NCG/EP composites.Details as follows:(1)Using a multimeter to measure the volume resistivity of NCG/EP composites with different curing temperatures and times,curing agent content,and conductive fillers.When the curing temperature is 140°C,the curing time is 60 mins,the ratio of EP/curing agent is 2.5:1.8,the curing is complete and the volume resistivity of the composite is minimum;when the average particle size of nickel-coated graphite is100?m,the volume resistivity of the composite is also the minimum,horizontal conductivity percolation threshold is 25 wt%.The scanning electron microscopy(SEM)results of the composites show that the structure of the NCG is complete and the NCG has a significant settlement phenomenon in the EP,and the delamination phenomenon is obvious.(2)Fumed silica was added to the composite system to obtain r-NCG/EP conductive composites.SEM results showed that the addition of fumed silica effectiively suppressed the settling of NCG in the matrix.The addition of fumed silica increased the G 'and ? of the composite,indicating that the addition of fumed silica increased the viscosity of the mixture and inhibited filler settling.However,the horizontal volume resistivity of the composite r-NCG/EP increases,indicating that the addition of the non-conductive component fumed silica is not conducive to the lateral conductivity of the composite.However,the perpendicular volume resistivity of the composite r-NCG/EP is greatly reduced.It shows that the composite material forms a conductive pathway longitudinally.(3)r-ENCG/EP conductive composite was prepared by EDA modification of NCG.The results of infrared and thermogravimetry tests of the modified NCG show that the coordination reaction between EDA and NCG occurs,and the N-Ni coordination bond is formed,and the modification does not destroy the structure of NCG.The ?,G ?and G ??of the EDA modified mixture all increased.The results showed that during the heat-treatment at 100° C/10 h,the N-Ni ligand partially reversibly reacted,resulting in the EDA showing the epoxy room temperature curing agent.The effect of partial curing with EP increased the viscosity of the system and further improved the settlement of NCG in EP.The SEM images of the composites and the modified composites show thatthe peak temperature of the composites decreases,and the larger enthalpy of heat indicates that the modification contributes to the dispersion of the fillers in the matrix.The volume resistivity of the EDA modified r-ENCG/EP conductive composite in the transverse and longitudinal directions is smaller than that in the unmodified system.The N-Ni coordination bond formed on the surface of the NCG can improve the dispersion by suppressing the aggregation between the particles,which plays an important role in the construction of the conductive path.