| With the popularization of electronic office and the improvement of intelligent level of production and life,electromagnetic radiation has more and more influence on people's work and life.Shielding coating has the advantages of low cost,simple preparation and strong practicability in all kinds of shielding materials.The traditional shielding coating is difficult to be prepared in the complex factory and office environment,while the movable flexible coating can meet this demand.In this paper,nickel / graphene / epoxy flexible composite coating was prepared on polyimide film by vacuum coating and spin coating.XRD,Raman spectrum and SEM were used to characterize the coating's structure and micro morphology.The process parameters of the coating preparation were optimized by single factor experiment.Then,it was discussed that how nickel powder content and graphene's amount influenced the coating's adhesion,hardness,flexibility,electromagnetic shielding performance and corrosion resistance.Meanwhile,we compared related properties of this composite coating with another flexible composite coating which is double-layer structure and prepared by copper coating on the substrate.The results shown follow:(1)The optimum technological conditions for the preparation of Ni / graphene / epoxy coating are: the size of nickel powder is 2 ? m,the content of nickel powder is 60wt%,the thickness of coating is 0.5mm,the content of graphene is 0.7wt%,and the thickness of copper film is 1 ?m.(2)It was found that the thickness of graphene was thinner and the defects were fewer.Inside the coating,nickel powder particles and graphene nanoflakes are connect with each other which produced,the coating's inner network structure.(3)With the augment of nickel powder content,the adhesion of the composite coating increased to peak value 5.1Mpa when the nickel powder content was 60wt%.However,when continued to increase the nickel powder,the adhesion decreased.The regulation is also suitable with graphene content.And we get the maximum value at 0.7wt% of graphene content.After coated with copper on the substrate,the total adhesion of this double-layer flexible composite coating descend to 4.6Mpa.(4)With the increase of the content of nickel powder,the hardness of the composite coating increases at the beginning and then decreases which is consistent with the regulation between graphene content and coating hardness.When the content of nickel powder is 60wt%,the maximum value is 14.03 HV.Meanwhile,the graphene content come at 0.5wt% and 0.7wt% produce the maximum value 14.03 HV.Compared with the composite coating,the hardness of the double-layer flexible composite coating with copper coating on the substrate has not changed significantly.(5)When the content of nickel powder in the composite coating increases,the overall flexibility of the coating shows a downward trend,and when nickel content is 20wt% and 30wt%,the best flexibility of the coating is 1mm,when the content of nickel powder is 60wt%,the flexibility of the coating is 2mm;with the increase of the content of graphene,the overall flexibility of the coating shows a first upward and then downward trend,and When the content of graphene is 0.3wt% and 0.5wt%,the flexibility of the coating is the best,which is 1mm.The flexibility of the double-layer flexible composite coating with copper coating on the substrate decreases to 3mm.(6)When the frequency of electromagnetic wave is 30MHz?1.5GHz,the average shielding effectiveness of flexible composite coating is 29.3d B.The average shielding efficiency of the double-layer flexible composite coating is 36.6d B.The electromagnetic shielding effectiveness of the double-layer flexible composite coating is obviously improved.(7)Through the research on the corrosion resistance of the coating,it is found that the corrosion resistance of the composite coating is generally excellent,while the corrosion resistance of the flexible composite coating with double-layer structure is slightly worse,with the corrosion resistance grade of 7. |
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