Study On Filled Composite Conductive Paints And Its Conductivity

High performance of aircrafts` invisibility to radar is hard to achieve due to the scattering of edges, gaps, grooves and steps. High conductive materials is used to keep the electrical continuities in order to avoid scattering. Silver powder has been the dominant choice for electrically conductive paints and repairing materials of electromagnetic discontinuities all the time owing to its high conductivity, excellent resistance for oxidation.After studying the mechanism of circuit forming, and other parameters that matters, the best processing parameters of preparing conductive paints, surface treatment of silver filler and preparation for silver flake by ball-milling are discussed. Contents and conclusions are as followed:Keeping some certain parameters constant, a series of experiment is conducted to value how many different ball-milling speed, solvent medium and ball-milling time have impacts on the surface morphology of silver flake and its size distribution, concluding the optimum process parameters are water as solvent medium, ball-milling speed of 200 rpm, and ball-milling time of 6 hour. The average particle size reach 12.3μm, and the surface resistance of conductive paint is as low as 0.068Ω/□, tensile strength is as high as 8.69 MPa.What influences surface modification with different coupling agent has on mechanical properties and conductivity of conductive coatings are studied. We confirm that the interfacial compatibility between conductive filler and resin matrix has significant effect on physical, electrical properties of conductive paints. The improvement of mechanical properties and electrical conductivity are results in proper amount of different coupling agent. When the usage of KH550 and KH560 both weight 1% of silver flake, the surface resistance reduces from 0.38Ω/□ to 0.066Ω/□, and the tensile strength keeps steady at 8.5mpa.Epoxy resin is chosen as the matrix resin, silver flake as filler, at the mass ratio of 3.75:1; mixed solvent(ethyl acetate, butyl acetat, butanone) with mass ratio of 2:1:1; solidifying temperature as 80℃, in 12 hour; multiple layers painting technique; curing agent with mass ratio 13% of epoxy resin. And finally the surface resistance reduce from 0.10Ω/□ to 0.039Ω/□, tensile strength increase from 8.5MPa to 13.9MPa.