Research On Preparation And Electromagnetic Shielding Properties Of Porous Polyimide-based Composites

With the rapid development of communication equipment,electronic instruments and the military industry,the demand for electromagnetic shielding materials in today's society is increasing.Polymer-based electromagnetic shielding materials have attracted much attention due to their advantages such as lightweight,good designability and good chemical resistance.At present,the development of polymer-based composite materials with high electromagnetic shielding properties has become a hotspot in this field.In this paper,a polyimide with good heat resistance was used as a matrix,and a hybrid filler was prepared as an electromagnetic wave absorber by graft modification/physical coating method.Then,porous polyimide-based electromagnetic shielding composites were prepared using in-situ polymerization and thermally assisted non-solvent induced phase separation(TNIPS).In this paper,graphene oxide(GO)with oxygen-containing groups on the surface was synthesized by Hummers method.Polyaniline was used to chemically graft the surface of GO to obtain polyaniline-modified graphene oxide(PANI-g-GO).The PANI-g-GO/MWCNT hybrid filler was obtained by the adhesion and coating of PANI chemically grafted on the surface of PANI-g-GO.With hybrid filler PANI-g-GO/MWCNT as electromagnetic wave absorbent,dibutyl phthalate(DBP)as porogen,using 4,4-diaminodiphenyl ether(ODA)and4,4-(4,4-isopropyldiphenoxy)diphthalic anhydride(BPADA)as monomers.A series of porous polyimide-based composites(PPIC)with different hybrid filler contents were prepared by in-situ polymerization and thermally assisted non-solvent induced phase separation(TNIPS).The structure and properties of the PPICs were characterized and analyzed by FT-IR,XRD,SEM,DSC,TGA,density test,hardness test,contact angle test,digital four-probe and network vector analyzer.FT-IR analysis showed that the thermal imidization of the porous polyimide composite was complete;XRD analysis showed that the addition of PANI-g-GO/MWCNT hybrid filler did not significantly affect the crystallinity of the polyimide;SEM analysis showed that the porous structures were successfully prepared inside and on the surface of the porous polyimide-based composite,and the hybrid filler had good compatibility with the PI matrix;DSC and TGA analysis showed that the porous polyimide-based composite has good thermal stability;The results of density and hardness test showed that when the hybrid filler content was 12 wt%,the density and hardness of the porous polyimide-based composite as low as 0.557g/cm~3 and 5.52;The results of contact angle test showed that when the hybrid filler content was8 wt%,10 wt%and 12 wt%,the surface of the porous polyimide-based composite had hydrophobic properties;The results of digital four-probe test showed that when the hybrid filler content was 12 wt%,the conductivity of the porous polyimide-based composite material can reach 160±5 S/m;The results of the network vector analyzer test showed that the porous polyimide-based composite had good dielectric loss characteristics,and when the hybrid filler content was 12 wt%,the total electromagnetic shielding effectiveness of the porous polyimide-based composite can reach 28.2 d B,which had excellent electromagnetic shielding performance.