Preparation And Electroforming Properties Of Epoxy Conductive Composite

Slush molding is a stress-free processing method,and its products have the characteristics of good dimensional stability,high pattern replication rate,and difficult to crack,so it is widely used in the field of automobile instrument panel manufacturing.As a key tool of the production of slush molding products,the quality of surface texture directly determines the performance of the slush molding products,and the quality of the surface quality depends directly on the production process of slush molds,especially in the preparation of epoxy master model.During the preparation of the epoxy master model it usually needs conductive treatment to meet the requirement of subsequent electroforming process because epoxy resin has a high degree of insulation.The common way of conductive treatment is silver spray,but due to the spray process reasons,it will causes the shallower depth of the texture on the surface of the master mold,which in turn affects the quality of the pattern.This research commenced with this issue and decided to develop an epoxy composite material with excellent conductivity,eliminating the need for a conductive treatment before electroforming process in order to improve the texture of the surface of the slush mold.In this paper,flaky silver powder?Ag?was first used as a conductive filler.Ag-EP composites were prepared with different contents of Ag powder after solution treatment.The effects of filler content on the properties of composite materials were investigated using four-probe resistance meters,rotational rheometers,scanning electron microscopy,etc.The results showed that after the treatment of mixed acid?7.2%HCl+19.8%H2SO4?,the carbon content on the surface of the flake silver powder decreased by 79.9%,indicating that the stearic acid on the surface of silver powder had been basically removed and the resistivity of flake silver powder was reduced to 74.3 m?·cm.Rheological experiments showed that after adding flake silver powder,the Ag-EP system behaved obvious shear thinning,the system modulus also increased sharply with the increase of filler content.Besides the filler has a positive effect on the curing of epoxy resin.As the content of Ag powder increases,the resistivity of the composite material Ag-EP decreases significantly,and when the filling content up to 100 copies,the resistivity of 100Ag-EP is 1.74×10⁴?·cm.Two kinds of carbon-based fillers,VGCF and GNP,were selected respectively,and conductive composites VGCF-EP and GNP-EP were prepared by solution blending.The effects of filler differences on the properties of composites were studied in this chapter.It was found that the in rheological experiments GNP-EP system had higher viscosity and modulus than VGCF-EP when the addition amount was the same.Comparing the frequency scan curve,the lamellar structure of GNP in the resin matrix is more likely to form a network and has a lower percolation threshold.In addition,the resistivity of GNP-EP composites is significantly lower than that of VGCF-EP.When the amount of GNP added is 10 parts,the resistivity is only 236?·cm,which is much lower than 10VGCF-EP.Finally,under the condition of the same total filler content,epoxy composite materials with dual network structure,V_xG_1-x-EP,were prepared by VGCF and GNP compounding.Studies had demonstrated that VGCF and GNP have a strong synergistic effect in the resin matrix.Through the complementarity of their structural differences,the two can more easily build a perfect three-dimensional network structure in epoxy resin,so the composite material VxG1-x-EP displayed more excellent electrical conductivity.When the total filler content is10 copies and the ratio of VGCF and GNP is 3:1,the resistivity of the composite material is142?·cm.Besides,several samples with certain differences in conductive properties were selected for electroforming experiments.It was found by comparison that the lower the resistivity of the composite material,the faster the surface deposition rate.On sample of10V_0.75G₀₂₅-EP,the weight after electroforming 24 h was increased by 19.39 g,and the maximum thickness of the nickel layer could reach 3.2 mm,while the plating quality of5VGCF-EP is only 1.69 g due to its high resistivity.