Preparation Of PAN/MWCNTs Micro/Nano-fiber Membrane And Microwave Absorbing Performance Of Its Laminated Structure Composites

In modern society, people have suffered from water pollution, air pollution, noise pollutionand electromagnetic pollution in daily life.Electromagnetic pollution is known as the fourth largestpollution and excessive microwave radiation has a serious impact on people’s health. Absorbingmaterials with carbon nanotubes have a wide bandwidth, light weight and good materialcompatibility, so they exhibit potential application in absorbing field. Electrospinning is thesimplest method to manufacture nanofibres and this technic is widely used in the filter material,biomedical material, tissue engineering and composite materials. In this study, a new type ofcomposite laminates was prepared by adding Multi-walled carbon nanotubes (MWCNTs) intoPolyacrylonitrile (PAN) solution for electrospinning and its application in absorbing areas wasexplored. This research had a certain reference and guidance for the study and application ofnano-absorbing materials and structural absorbing material.Firstly, in order to explore the optimal electrospinning parameters of PAN solution and obtainmicro/nano-fiber membrane with stable structure and performance, Orthogonal experiment wasexplored to study the effect of three important spinning parameters (PAN solute concentration,applied voltage, and receiving distance) on electrospinning of PAN solution. The study observedSEM, diameter distribution of PAN nanofibers associated with orthogonal test was analyzed, Itwas demonstrated that the concentration of PAN solution was the most important processparameters which influenced the diameter of the nanofibers. Then the optimum process wasobtained.Secondly, according to the optimum electrospinning process parameters of above PANmicro-nano fiber membrane, MWCNTs was added into PAN spinning solution to preparePAN/MWCNTs micro-nano fiber membrane. In order to improve the uniformity and stability of dispersion of MWCNTs in PAN solution, carboxyl groups were grafted to MWCNTs by acidizingtreatment. Then, the influence of the mass fraction of MWCNTs on properties (viscosity andconductivity) of PAN solution was studied. The results showed that with the increasing of massfraction of MWCNTs, the viscosity and conductivity of the mixed solution increased. The impactof MWCNTs on the structure and properties of resulting micro-nanofiber membrane were studiedby the distribution of MWCNTs in PAN/MWCNTs micro-nano fibers using SEM and diameteranalysis software. The results indicated that the fiber diameter, coefficient of variation, tensileperformance and electrical properties of PAN/MWCNTs micro/nano-fibers wereMWCNTs-ralated changes..Finally, a new absorbing composite material with multi-layer structure was prepared.Glassfibers and epoxy resin were acted as a wave-transparent material and PAN/MWCNTs micro-nanofiber membrane was acted as absorbing material, VARTM method was used to curePAN/MWCNTs micro-nano fiber membrane laminate to explore its microwave absorbingperformance. Test results showed that when the mass fraction of MWCNTs was below percolationthreshold, which was25wt%, shielding effectiveness increased with increasing of MWCNTs massfraction.When mass fraction exceeded the percolation threshold, the polarization of the materialweakened, which caused the attenuation of the electromagnetic wave energy decreases.Withincreasing of MWCNTs mass fraction, the frequency corresponding to the curve peak of eachelectromagnetic shielding plate was on a shift to lower frequency.This research also compared shielding effectiveness between single and multi-layerPAN/MWCNTs micro-nano fiber membrane laminate. The test result showed that when the massfraction of MWCNTs was25wt%, electromagnetic shielding performance of laminate with tenlays PAN/MWCNTs micro-nano fiber membrane increased significantly. In addition, the shieldingeffectiveness of different superimposed layers of laminated plates was investigated and it showedthat electromagnetic shielding effectiveness after superposition is approximately equal to the sumof shielding effectiveness of each Laminate, and with increasing of the number of laminates, theshielding effectiveness is larger, the frequency corresponding to the absorption peak shifted tohigh frequency. At the same time, shielding width increased largely with increasing of the numberof laminated plates.