Study On Preparation And Electromagnetic Shielding Properties Of Cellulose-based Highly Conductive Film

With the wide use of electronic products and communication systems in commercial,military,scientific and other fields,electromagnetic radiation pollution is increasingly aggravated and serious harm.Therefore,it is urgent to develop high-performance electromagnetic interference(EMI)shielding composite materials.In light of the shielding requirements of "lighter,thinner and stronger",the lightweight and flexible conductive polymer composites(CPC)have become a current research hotspot.Cellulose is the most abundant natural polymer currently known.Cellulose paper is a kind of flexible porous composite material prepared from cellulose,which has good adsorption properties and can be combined with conductive fillers to make EMI shielding composite material used in a variety of fields.However,cellulose paper has poor water resistance and is prone to moisture,resulting in the life cycle and scope of application is limited.In addition,the type and content of fillers will also affect the shielding efficiency(SE)of CPC.Therefore,the development of lightweight flexible cellulose composite films with low filler content and high EMI SE is the focus of this subject.Based on the above problems,this paper first uses silver nanowires(AgNW)with high conductivity and large aspect ratio as fillers to prepare composite materials.We fabricated hydrophobic AgNW/cellulose composite films by efficient and simple dip-coating process and coating method.SEM shows that AgNW interweave tightly attached to the surface of cellulose paper,which gives the composite film high electrical conductivity(33.69 S/cm,in-plane direction).Owing to multiple reflection and scattering of electromagnetic waves between the two highly conductive surfaces,the obtained composite film presented a high EMI SE(46 dB)and ultra-high specific shielding effectiveness(271.2 dB mm-1),when dip-coating 10 times.At the same time,due to the presence of the inorganic hydrophobic coating on the outside of the composite film,the surface water contact angle is as high as 140°,exhibiting good waterproofness and antifouling performance,and oxygen-resistant protection against AgNW.In addition,the resulting hydrophobic AgNW/cellulose composite film can still maintain high EMI SE and waterproof performance after dozens of bending or thousands of peeling tests,showing high stability and reliability.Secondly,two-dimensional(2D)conductive filler graphene nanosheets(GNSs)were introduced.Two kinds of PVDF-AgNW/GNSs/cellulose composite films(CGA and ACG)with different structures and excellent mechanical flexibility was fabricated via vacuum filtration to attach GNSs to the cellulose paper side and simply surface coating process.The ACG with conductive fillers distributed on both sides shows excellent flexibility and EMI SE of over 39.3 dB.Highly reliable shielding ability is achieved with 94%EMI SE retention after 100 folding cycle tests.The CGA with conductive filler distributed to one side shows a high EMI SE of 53.3 dB against the X band and an ultra-high specific EMI SE of 313.5 dB mm-1.As a new paper-based EMI shielding composite,CGA and ACG will provide more convenient strategies for different EMI shielding requirements.