The Study On Ag/Graphene Unsaturated Polyester Resins Electrical Conductive Adhesive

As the development of electronics industry and technology, traditional tin/lead solder have been replaced by electrical conductive adhesive owning to its low energy costing, eco-friendly, and simple operation process. In this study, we focus on preparing a novel electrical conductive adhesive with high shear strength, high electrical conductivity and good thermal stability. In this adhesive, the conductive filler was obtained by mixing graphene and Ag nanoparticles together and further added into the unsaturated polyester resin to give the final product.The preparation of Ag loaded graphene (Ag-G) was started from natural flake graphite. According to the modified Hummers method, graphite oxide was obtained and further treated under ultrasonication to prepare the graphene oxide. In the next step, AgN03 solution was added to the graphene oxide and chemical reduced by the facile reductant sodium borohydride (NaBH4) to give the Ag-G conductive filler. To synthesize the unsaturated polyester resin which could cure at room temperature, phthalic anhydride, maleic anhydride, diethylene glycol, glycerol were used as the reactant, styrene as diluting agent and crosslinking agent, cobalt naphthenate as curing agent, methyl ethyl ketone peroxide as a promoter. The final Ag-G electrocial conductive adhesive was prepared by mixing the as-prepared Ag-G conductive filler and the unsaturated polyester resin.To characterize the Ag-G, transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectrum (Raman), and X-ray photoelectron spectroscopy tester (XPS) were applied. The results indicated that, Ag-G has been prepared successfully. And, to study the optimal reaction time of synthesizing the unsaturated polyester resin,Acid value detection and Fourier trans- form-infrared spectroscopy (FT-IR) were conducted. And it could be deduced that 4 h is the optimal reaction time from the results. The shear strength was also studied by a universal testing device. When the content of the curing agent, cobalt naphthenate, was 2.0 wt%, the adhesive exhibited a high shear strength of 5.7 MPa, curing time of 53.7 s, and a good thermal stability.For the electrical conductive adhesive, the relationship between the electrical conductivity (k) and the content of conductive filler was estimated by a four point probe resistance measuring instrument. As the increasing of the conductive filler, the electrical conductivity increased but scarcely changed when the content of Ag-G is higher that 25wt%. The shear strength decreased as the addition of conductive filler. The thermal property was carried out through thermogravimetric analysis (TGA). From the obtained curves of TG and DTG, the initial temperature of thermal degradation (t0), the maximum weight loss rate (Dm) as well as the temperature of maximum weight loss rate (tm), and the final carbon residue quantity (w) were obtained. All the data indicated the electrical conductive adhesive prepared in this study exhibited a good thermal stability.