Preparation And Electromagnetic Shielding Properties Of Wood-based Cellulose Nanofible/Polyaniline Film

Wood-based cellulose nanofiber(CNF)is a new product of poplar.Due to its high aspect ratio,good biocompatibility,and sustainability,CNF can be a good matrix in composite materials.However,CNF has limited its development in practical applications due to its own defects.As a typical conductive polymer,polyaniline(PANI)has been attracted by more and more attention due to its excellent physical and chemical properties,unique doping mechanism,controllable dielectric properties,and wide absorption band.However,the solubility and melting properties of pure PANI are poor,resulting in poor mechanical properties.In addition,PANI particles are tightly packed together,which hinders ion transmission and affects its final properties.This paper first analyzes the CNF element and the PANI element separately,and then uses CNF as the matrix to make PANI polymerized in situ on the surface of the CNF to form a CNF/PANI film.The CNF/PANI composite film can not only solve the problem of CNF in practical applications.Limitation also improves its thermal stability and water resistance,also improves the poor mechanical properties of PANI,gives PANI good flexibility,and improves the conductivity of the sample,thereby achieving the ultimate effective electromagnetic shielding effectiveness.The research content of the paper is as follows:(1)Preparation of CNF by chemical pretreatment combined with ultrasound,then using CNF as the matrix,HCL as the dopant,and ammonium persulfate as the initiator,the conductive polymer PANI was polymerized and deposited on the surface of the CNF by ANI in-situ chemical polymerization,forming a CNF/PANI nanocomposite film with a heterogeneous core-shell structure.SEM images show that the diameter of CNF ranges from 15 to 40 nm,and the length of CNF fibers is about 150-350 nm.The eigenstate PANI shows fine particles,and the main form of doped PANI is "holothurian-like " structure.From the TEM image of PN50,the core-shell structure formed by the PANI coating on the surface of the CNF was observed.The diameter of the CNF core was 23 nm,and the thickness of the PANI shell was 7 nm.(2)Cellulose and CNF films will absorb moisture and swell when they encounter water,and PANI has good hydrophobicity.Test the durability and flexibility of composite film materials,and explore the practical application of composite film materials.CNF/PANI nanocomposite film was immersed in water for 1 month,and it was found that CNF/PANI nanocomposite film showed good water resistance,and CNF/PANI films with different PANI filler content showed good flexibility,even if the content of PANI filler was 50wt%.Analyze the thermal stability of the composite film according to the TG data.When heated to 700?,comparing with virgin cellulose(12.7%),PANI,PN50,and CNF showed higher carbon residue rates,which were 63.2%,41.3%,and 27.5%,respectively.(3)The conductivity of the PN50(2.27 S·cm-1)film measured by a four-probe resistance tester is greater than that of the doped PANI(1.04 S·cm-1),and the dielectric loss is generally considered to be the cause of electromagnetic wave energy loss in non-magnetic materials.The ? value of the PN50 composite film is calculated to be?1.48.According to the EMI analysis of the shielding performance of the sample and analysis of its shielding mechanism,the results show that the PN50 composite film with a thickness of 0.28 mm has an electromagnetic shielding effectiveness of 25.2dB in the range of 8.2-12.4 GHz.Moreover,the unique core-shell structure of PN50 film also has a significant impact.