Molding And Electromagnetic Interference Shielding Performance Of Flexible And Ultrathin Chopped Carbon Fiber Composites

Miniaturization and integration of electronic circuits and components have put forward requirements for lightweight and flexible electromagnetic shielding materials.In addition,in some specific fields,materials are also required to have high absorbing properties to prevent secondary pollution of electromagnetic waves.Lightweight and flexible electromagnetic shielding materials with high shielding effectiveness or high absorbing properties have gradually become a hot topic in recent research.Therefore,this paper proposed a manufacturing method by combining wet-papermaking method with heat-pressing technology.A flexible and ultra-thin EMI shielding material(referred to as CEF-NF)is prepared with chopped carbon fiber.Based on this material,functional materials with high absorbing properties or high electromagnetic shielding properties that can be applied in different fields are designed and prepared separately.The main work and conclusions of this paper are as follows:(1)Proposed a two-step method – combining a wet-papermaking method with heatpressing technology.The CEF-NF material prepared by chopped carbon fiber and chopped polypropylene/polyethylene fiber(this fiber is a polypropylene/polyethylene sheath-core fiber)has excellent flexibility and mechanical stability.(2)Based on the previous research,investigated the effect of process parameters and structural parameters on its EMI shielding performance.We found that the conductivity percolation threshold of CEF-NF material has a great influence on the power coefficient.When the concentration of the chopped carbon fiber reaches the percolation threshold,the absorption coefficient A reaches its peak value.In addition,the secondary lamination of CEF-NF and PC film can improve its mechanical properties without affecting its electromagnetic shielding performance.(3)The CEF-NF material was used as the surface modification carrier,then we combined electroless nickel deposition and secondary lamination to produce a high EMI performance,compact,ultra-thin and flexible film with good mechanical strength(referred to as Ni plated CEF-NF/PC composite).Its electrical properties,EMI shielding performance,and mechanical properties have been investigated in detail.The experimental results show that the electroless nickel deposition can effectively improve the EMI shielding performance of the material.After mechanical bending for 5000 times and heating at 120 °C for 50 h,the Ni plated CEF-NF/PC film still maintained 96.36% of its EMI shielding effectiveness.(4)Based on the percolation threshold theory,CEF-NF materials and polycarbonate film were laminated to prepare a chopped carbon fiber reinforced resin with multi-layer structure composite(referred to as multi-layer CEF-NF/PC composite).Investigated and clarified the actual shielding performance and potential shielding performance of EMI shielding materials.The experimental results show that the multi-layer structure has a great effect on improving EMI shielding performance.