Fabrication And Properties Of Electrospun PI/Fe₃O₄ Composite Fibrous Membrane

The main electromagnetic shielding materials are mainly composed of composite conductive polymer materials at present.However,the shielding effect of this kind material is often affected by the filler particles dispersed in the polymer matrix,the promblem of low efficiency and the shielding effect is not stable.Therefore,it is imperative to model eletromagnetic shielding materials and the development of lightweight high efficiency.In this paper,a coprecipitation method was used to prepare iron oxide（Fe₃O₄）magnetic nanoparticles.X ray diffraction（XRD）and transmission electron microscop（TEM）analysis showed that,the prepared Fe₃O₄ particles were spinel structures with an average particle size of about 80 nm.The Fe₃O₄ magnetic nanoparticles were prepared by using the method of in-situ polymerization,and the PI/Fe₃O₄ composite fibrous membrane was prepared after electrostatic spinning and thermal imization.The PI/Fe₃O₄ composite fibrous membrane was prepared by electrospinning technology.By using Fourier transform infrared spectroscopy（FT-IR）,transmission eletron microscopy（TEM）,scanning electron microscopy（SEM）,X ray diffraction（XRD）,thermogravimetric（TG）analysis of morphology and structure of the composite fiber membrane;The broadband dielectric spectrometer,broadband dielectric spectrometer,hysteresis curve instrument（VSM）and vector network analyzer were used,which analysised PI/Fe₃O₄ composite fibrous membrane dielectric properties,magnetic properties and electromagnetic shielding.The effects of liquid solid content,Fe₃O₄ nanoparticle addition,spinning voltage,injection speed and drum speed on themorphology and properties of electrospun PI/Fe₃O₄ composite fiber were discussed in details.By scanning electron microscopy,the best electrospinning process was obtained by analyzing the morphology of the composite fibrous membrane with different electrospinning processes.The specific process parameters are as follows:the eletrospinning voltage is 20 kV,the injection speed of the solution is 0.3 mL/h,and the speed of the receiving roller is 5000 rad/min.The fiber in the composite fiber membrane prepared by this process is uniform and without bead section,and the ratio of fiber wire under 5 degrees is up to 30%.The results of FT-IR showed that,the introduction of Fe₃O₄ magnetic nanoparticles does not destroy the chemical struture of PI molecules;The performance test results showed that,when the Fe₃O₄content is 1 wt%,composite fibrous membrane has the best mechanical properties,the tensile strength is 10.9 MPa,the elongation is 18.6%;TG analysis results showed that,the composite fiber membrane thermal decomposition temperature is increasing with the Fe3O4 particle content;when content of Fe3O4 is 7 wt%composite fiber,the decomposition temperature pure PI fiber membrane was 550℃,the thermal decomposition temperature with Fe₃O₄ content of 7 wt%is 562℃,which increased by 12℃compared than the pure film.The dielectric spectroscopy results showed that,the dielectic constant of the composite fibrous membrane increased with the increase of Fe₃O₄ content,and the dielectic loss also appeared a slowly growth trend.When Fe₃O₄ content is 7 wt%,dielectric constant of the composite fiber membrane reaches 1.92/10¹ Hz,the dieletric loss is 3.8×10^-3/10¹ Hz;hysteresis curve analysis showed that,the Fe₃O₄particles were prepared by magnetic domain has good performance,the saturation magnetization,esidual magnetization and the coercivity values were 79 emu/g,and9.5 emu/g,63 Oe.With the content of the nano-Fe3O4 particles,magnetic composite fibrous membranes were increased;electromagnetic shielding performance analysis results showed that,when the shielding band in 8.2-12.8 GHz,the Fe₃O₄ addition amount was 7 wt%,The shielding effect reached 35 dB and the shielding effect was good.