Study On The Ifeld Conductive Cffect And Thixotropv Of The Nickel-coated Graphite/Two-componcnt Silicone Rubber

With the development of the electronic industry and the miniaturization ofelectronic equipment, the application field of conductive composite adhesive wasexpanding. The requirements of the conductive property, the stability and theconstruction method of it from people was enhance. In this paper, the high conductivesilicone rubber composite material were prepared with nickel coated graphite (NCGPs)as conductive filler and two component silicone rubber as blowing agent matrix. Theinfluencing factor of mechanical property and conductive property, and the conductionresponses of composite material under the external field, including the tensile,compression, temperature, electric field. he results show that:(1)The tensile strength and elongation rate of composite material were increasedwith the increase of the content of NCGPs. and both go to the best when the content ofNCGPs betweet50%to54%. The surface treatment of NCGPs can effectively improvethe compatibility between the filler and the matrix materials. And the heat treatmentgood for improve the mechanical property of composite material. At the same time,with the content of fillers increasing, the conductive percolation phenomenon occurred,and the percolation threshold was46%~48%.(2) The electrical resistance of composite material present a step-like rise underuniaxial tension. This relates to the flake shaped of the conducting particles. In thecreep and stress relaxation experiments, the electrical resistance variation curves of thecomposite material were similar to the polymer’ creep and stress relaxation curves, thissuggests that the conductive structures inside the composite material and the matrixstructure were not only independent, but also interrelated. The cycle loading made thematerial occursed permanent deformation, so the electrical resistance baseline was rise.(3) The electrical resistance of composite material was enhance with the increase oftemperature, exhibited aclearly positive temperature coefficient effect (PTC), and thepositive temperature coefficient effect was weaken with the increase of filler rate. Thecycle heating made the material occursed electrical resistance relaxation phenomenon,that can improve the stability of conductive networks.(4) The low electric current wasn’t enough to make conductive network inside the composite material to move, but when the electric current raise to5A, the electricalresistance had a clearly increasement, that suggests that the conductive structures insidethe composite material and the matrix structure both were independent and interrelatedagainst.(5) The viscosity of compound adhesive had a closely relation with the rotorspeed, shear time, temperature, the nickel content of NCGPs, particle diameter,thixotropic agent. The viscosity was increase with the quicken of rotor speed under theshear system, this revelation that there was exist a competition regime betweenreconstruction and damage of the conductive network inside the compound adhesive.The viscosity curve of compound adhesive became to a closedloop undergo thecyclic Shear at the speed from0r/min to500r/min, that was electrical resistancehysteresis phenomena.(6) Increase the temperature made the viscosity of compound systems rised. Thecompound systems with large particle size fillers had a better thixotropy, but had abader mechanical property. Under the same shear history, the viscosity of compoundsystems with smaller particle size filler was smaller. The shear time dependence ofviscosity was stronger at low shear rates. The shear-thinning effect was best when thecontent of thixotropic agent was2phr.