Study On Preparation Of Conductive Polymer/Carbon Material Composites And Their Electromagnetic Shielding Properties

With the rapid development of science and technology,electromagnetic(EM)wave pollution is becoming more and more serious,EM radiation has adverse effects on precision equipment and human health.EM shielding materials can effectively reduce the problems related to EM.The easily-dispersible C60,ferrocene modified graphene oxide and ferrocene modified ethylenediamine functionalization graphene oxide were chosen to prepare a series of conductive polymer/carbon material composites by in-situ chemical oxidation polymerization with aniline(ANI)and pyrrole,respectively.Their EM shielding properties and mechanism were studied.The main work of this paper is as follows:(1)A total of 22 PANI/C60 composite samples were prepared by in-situ chemical oxidation polymerization method at different reaction conditions(concentration of aniline,concentration of C60,concentration of doped acid H2SO4 and reaction temperature).The structures and compositions of the prepared samples were characterized by FT-IR,XRD and XPS,and the morphologies of the samples were observed by SEM and TEM.The electrical conductivity of the samples were determined by a four-probe method.The possible formation mechanism of PANI/C60 composites was discussed and the optimal synthesis conditions were determined(Sample-12:ANI/K2Cr2O7=5.74:1(molar ratio),[H2SO4]=3.5 mol/L,ANI=1 mL,reaction temperature T=0?).The EM shielding performance of PANI/C60 composites was tested in the frequency range of 1?4.5 GHz,and the effect of electrical conductivity on the EM shielding performance of the composites was studied.It was found that when 50 wt%Sample-12 was added to the paraffin matrix,the average EM interference shielding efficiency(EMI SE)was the highest,reaching about 23.01 dB.This may be due to the interfacial polarization generated by the heterogeneous interface between PANI and C60,which effectively consumed the EM wave.In addition,the conductive network provided by PANI contributed greatly to the electron transition,which further improved the EM shielding performance.Meanwhile,the multiple reflections of EM waves inside PANI/C60 could convert more EM waves into thermal energy.Besides,a large number of poles and dipoles on PANI could also caused EM loss.(2)Ferrocene-modified graphene oxide(GO-Fc and GO-Fc-GO)were prepared by acyl chlorination of ferrocene-monoformic acid(FcCOOH)and 1,1'-ferrocene-dicarboxylic acid(Fc(COOH)2),and then reacted with the-OH on the surface of GO.Polypyrrole nanotube/ferrocene modified graphene oxide composites(PNT/GO-Fc and PNT/GO-Fc-GO)were prepared by in-situ chemical oxidation polymerization using methyl orange as template.The structures,compositions,morphologies and thermal stability of the prepared samples were characterized by FT-IR,XRD,EDS,XPS,SEM,TEM,TGA and Raman.The conductivity of the samples were measured by a four-probe method,and the effect of the conductivity on the EM shielding performance of the composites was studied.FT-IR,XRD and EDS results demonstrated that the GO surface was modified by ferrocene groups,and PNT/GO-Fc and PNT/GO-Fc-GO composites were successfully prepared.Raman test results also showed that ferrocene groups successfully modified GO surface,and there were interactions between the two groups.XPS results illustrated that compared with GO,the content of C-OH on the surface of GO-Fc and GO-Fc-GO was significantly reduced,which was consistent with the introduction of ferrocene groups through the method of reacting with-OH.SEM and TEM observations showed that the surface roughness and thickness of the modified GO were increased,while the PNT had a hollow rod structure with a length of about ten microns and a diameter of several hundred nanometers.The EM shielding properties of the composites were studied by coaxial method in the frequency range from 1 to 4.5 GHz,test results demonstrated that the EMI SE value of PNT/GO-Fc-GO composite prepared by adding 50 wt%to the paraffin matrix was 20.8 dB,this may be due to the interactions between the conjugated system formed by GO-Fc-GO and PNT,such as ?-? stack,hydrogen bonding and electrostatic force,which accelerated the electron transmission in the composite material and improved the electron transition ability.,at the same time dipole polarization,interfacial polarization between heterogeneous interfaces and multilevel reflections within the material further improved the EM shielding performance of the composite.(3)After acyl chlorination of FcCOOH and Fc(COOH)2,ferrocene-modified ethylenediamine functionalized graphene oxide(GO-EDA-Fc and GO-EDA-Fc-EDA-GO)were prepared through the reaction with an epoxy-group bridged ethylenediamine on the GO surface.Polypyrrole nanotube/ferrocene modified ethylenediamine functionalized graphene oxide composites(PNT/GO-EDA-Fc and PNT/GO-EDA-Fc-EDA-GO)were prepared by in-situ chemical oxidation polymerization using methyl orange as template.The structures,compositions,morphologies and thermal stability of the prepared samples were characterized by FT-IR,XRD,EDS,XPS,SEM,TEM,TGA and Raman.The conductivity of the samples were measured by a four-probe method,and the effect of the conductivity on the EM shielding performance of the composite was investigated.FT-IR,XRD and EDS results showed that the bridging of ethylenediamine,the introduction of ferrocene groups,and the successful preparation of PNT/GO-EDA-Fc and PNT/GO-EDA-Fc-EDA-GO composites.Raman test results also illustrated that the ferrocene groups successfully modified the functionalized GO,and there were interactions between the two groups.XPS results showed that the Fe element with Fe(?)was given priority to,a small amount of Fe(?)could be due to some ferrocene by oxidation.SEM and TEM observations demonstrated that there were no significant difference between the morphologies of ethylenediamine functionalized GO and GO,while the surface roughness and thickness of functionalized ethylenediamine modified by ferrocene groups increased,and the folds decreased.The EM shielding properties of the composites were studied by coaxial method in the frequency range from 1 to 4.5 GHz,test results showed that the EMI SE value of PNT/GO-EDA-Fc-EDA-GO composite prepared by adding 50 wt%to the paraffin matrix was 28.7 dB,this may be due to the interactions between the larger and more stable system formed by GO-EDA-Fc-EDA-GO and PNT,such as ?-? accumulation,hydrogen bond and electrostatic force,which accelerated the transfer rate of electrons in the composite material,thus increasing the electrical loss of EM waves.Dipole polarization,interfacial polarization between heterogeneous interfaces and multilevel reflections in the material were all beneficial to the improvement of EM shielding performance of composite.In conclusion,the prepared PANI/C60,PNT/GO-Fc-GO and PNT/GO-EDA-Fc-EDA-GO composites have good application prospects in the field of EM shielding.