Research On The Preparation And Properties Of Lightweight Poly (Ether Ether Ketone) Electromagnetic Shielding Materials

With the development of electronic and information technology,electromagnetic wave has been widely used as an important carrier of information dissemination.At the same time,it also leads to the complex electromagnetic pollution.In the past decades,the development of electromagnetic interference(EMI)shielding materials with excellent comprehensive performance has became a research focus,in which the foams based on polymeric composite have attracted much attention due to its light weight,low volume fraction of the fillers and so on.Poly(ether ether ketone)(PEEK)is a kind of special engineering plastics with excellent comprehensive performance and has a wide market in the automotive,aerospace,electronic,medical and other fields.Therefore,in order to broaden the application fields of PEEK and make full use of the advantages of special engineering plastic,it is of great significance to develop crystalline PEEK foam and its EMI shielding foams.Firstly,we choose the crystalline PEEK sheets as the research object by pressure-quenching foaming,and systematically studied the influence of melt index,crystallinity,saturation temperature,saturation pressure,saturation time,depressurization rate and cooling medium on the cell morphology through screening of matrix resin and foaming process parameters.A series of crystalline PEEK sheet foams with volume expansion ratio of 1.78-7.11,cell density of 5.18×108-7.7 ×107cells/cm3,cell size of 11-45 ?m were successfully prepared.In the frequency of Ku band,the shielding effectiveness(SE)of PEEK foam is low.Although the porous structure in the foam can lead to the multi-reflection of the electromagnetic wave in the material,it can not make up for the loss caused by the intrinsic insulation of the matrix.In addition,crystalline PEEK foams have excellent heat resistance and corrosion resistance.In order to further improve the EMI shielding properties of crystalline PEEK foams,we choose multi-walled carbon nanotubes(MWCNTs)as conductive filler,and selected poly(ether sulfone)(PES)that has good compatibility with PEEK,coating on MWCNTs(PES@MWCNTs)to improve its dispersibility in PEEK matrix.It should be noted that the addition of MWCNTs has multiple effects.It can not only increase the melt viscosity of the system,but also play an important role of heterogeneous nucleation in the foaming process.Then,a series of PES@MWCNTs/PEEK composite foams were prepared by optimizing the foaming conditions.In the frequency of Ku band,the specific SE of 3 wt%PES@MWCNTs/PEEK composite foam with the density of 0.39 g/cm3 is as high as16.46 dB g-1 cm3,which was 7 dB g-1 cm3 higher than the un-foamed composite,and the absorption loss is significant.With the frequency from Ku to Ka band,the SE of composite foams increase gradually.Moreover,with the same MWCNTs content,the SE of composite foams is higher with the higher cell density and the smaller cell size.In addition,composite foams have excellent heat resistance and corrosion resistance.In a word,PES@MWCNTs/PEEK composite foams can be used as a new type of lightweight,broadband and absorption type electromagnetic shielding materials.