Preparation And Electromagnetic Interference Shielding Properties Of Lightweight Polyetheretherketone Composites

With the rapid development of electronic equipment,especially the rise and commercialization of 5G network communications,electromagnetic waves have penetrated into all aspects of human production and life as a carrier of information transmission,has brought us great convenience.However,the rapid development of communication technology and electronic equipment has also complicated the electromagnetic environment around us,and electromagnetic pollution has become one of the most serious environmental problems all over the world.The emergence of electromagnetic interference?EMI?shielding materials has effectively alleviated the problems above.However,with the progress of the times,society has put forward higher and higher requirements for the comprehensive properties of EMI shielding materials.EMI shielding materials not only need to have a certain shielding effectiveness,but also need to be lightweight.Especially in areas where weight loss is the main factor,such as aviation,aerospace and portable electronic equipment.Therefore,it is urgent to develop lightweight,high-performance electromagnetic shielding composites.Polyetheretherketone?PEEK?,as a semi-crystalline polymer material,belongs to special engineering plastics.It has the advantages of high thermal resistance,radiation resistance,chemical resistance,impact resistance,creep resistance,good flame retardancy,and excellent electrical properties.And it has been widely used in high-speed rail transportation,new energy vehicles,efficient transportation technology and equipment,aerospace,electronics,information and defense fields.However,PEEK as a polymer material,has very poor electrical conductivity due to its structural characteristics:PEEK molecules are made up of a large number of atoms connected by covalent bonds,and non-bonded electrons are bound to a single atoms cannot form effective carriers,so they have extremely poor conductivity and do not have EMI shielding properties.Therefore,introduce conductive fillers into the PEEK matrix to prepare polyetheretherketone-based composites could not only take the advantage of PEEK as a special engineering plastic,but also give the composites high shielding effectiveness,has important application significance.In this thesis,PEEK was chosen as the matrix and HALS-3346 as the chemical foaming agent,and then the PEEK foams were fabricated via compression moulding process.Through the adjustment of process parameters such as the chemical blowing agent content,foaming temperature and foaming pressure,the cell structure can be regulated to a certain extent.The research results show that the PEEK foams has high compressive strength,excellent thermal stability and good solvent corrosion resistance.So,it can meet the performance requirements of foam materials in some special fields such as aviation,aerospace and military.In addition,we provide a certain theoretical basis and technical support for the development of high-performance foam materials.In order to develop lightweight and efficient EMI shielding composites,we introduced carbon fiber?CF?and carbon nanotubes?CNT?as hybrid conductive fillers into the mixture of PEEK and HALS-3346 and prepared a series of lightweight porous PEEK/CF/CNT composites.The effects of the total content of conductive filler and the ratio of CF and CNT in the filler on the properties of the composite were discussed.The research shows that the PEEK/CF/CNT composite has a porous structure,and the density is significantly lower than that of pure resin.And the conductive fillers overlap each other in the resin matrix,forming a perfect 3D conductive network.The test results show that the composites has good conductivity and electromagnetic shielding effectiveness,and the composites exhibits an absorption-based shielding mechanism.The study found that with the increase of filler content,the density of the composites increases,the porosity decreases,and the electrical conductivity and electromagnetic shielding efficiency are increasing.When the filler content is the same,the density and porosity of the composites are basically the same,and the conductivity and shielding effectiveness of the material increase with the proportion of CNT in the filler.The PEEK/CF10/CNT10 composite,which possess a density of only 0.672 g/cm³,has a electrical conductivity of 10.14 S/m,and the shielding effectiveness in X-band reaches54.68 dB,and the specific electromagnetic shielding effectiveness is as high as 81.62dB cm³ g^-1.In addition,the composites show a good thermal stability.In summary,we provide a simple and efficient strategy for preparing lightweight carbon materials/polymer electromagnetic shielding composites,which can achieve excellent shielding effectiveness at a relatively low filler content.