Preparation And Properties Of Hollow Mesoporous Carbon Microspheres/MWCNT/Polyurethane Electromagnetic Shielding Composites

With the rapid increase of intelligent communication equipment,electromagnetic pollution is getting worse,and the research and application of high-performance electromagnetic shielding materials have attracted great attention from academic and engineering circles.Traditional metal-based electromagnetic shielding materials have high reflection loss and high density and are difficult to process.Conductive polymer materials with carbon materials as fillers have the advantages of flexibility,light weight,corrosion resistance,and low processing cost.They have become the research field in electromagnetic shielding in recent years.One of the hot spots.However,the conductivity of conductive polymer materials is not high.Therefore,how to improve the electromagnetic shielding performance and increase the proportion of absorption loss under the condition of low density has become a key issue for polymer-based electromagnetic shielding materials.In order to solve the problems in practical applications,this paper prepares one-dimensional,two-dimensional,and three-dimensional electromagnetic shielding materials from the three dimensions of point,surface and volume.By manufacturing hollow mesoporous carbon(MCHMs)fillers with different average particle sizes.The influence of microstructure on electromagnetic wave absorption performance was discussed.The influence of the content of multi-walled carbon nanotubes(MWCNT)and MCHMs on the electromagnetic shielding performance of waterborne polyurethane(WPU)film composites was discussed.The influence of density on the electromagnetic shielding performance of MWCNT/MCHMs/WPU/polyvinyl-alcohol(PVA)foam composite was discussed.The main contents are as follows:(1)A hard template etching method was used to manufacture hollow mesoporous carbon microspheres(MCHMs).Adjust the structural characteristics of MCHMs by adjusting the content of resorcinol and formaldehyde.When the average particle size of MCHMs is 452 nm,paraffin composites containing 10wt%MCHMs can achieve a maximum reflection loss(RL_min)of-51 dB and an effective absorption bandwidth(EAB)of 3.92 GHz.When the average particle size of MCHMs is 425 nm,the RL_min of the paraffin wax composite containing10wt%MCHMs is-22 dB,and the EAB is 7.14 GHz.Excellent electromagnetic wave absorption performance is obtained by rationally designing the microstructure.(2)MWCNT/MCHMs/WPU composites were prepared by solution mixing method,with 20wt%,40wt%,60wt%MWCNT and 40wt%MWCNT/10wt%MCHMs as fillers.Study the influence of different MWCNT content and MCHMs on the electrical conductivity,electromagnetic shielding performance and mechanical properties of polyurethane composites,and explore the relationship between composite structure and performance.WPU/60wt% MWCNT has a conductivity of 95.4 S/m and an electromagnetic shielding efficiency of 40 dB(X band)at a thickness of 0.6 mm;adding 10wt% to the composite material of WPU/40wt% MWCNT can improve the conductivity of the composite material.The electromagnetic shielding effectiveness were increased from 51.2 S/m to 55.4S/m,and from 30 dB to 33 dB.The research results show that increasing the content of MWCNT and adding MCHMs are beneficial to improve the electrical conductivity and electromagnetic shielding performance of the composite.(3)The MWCNT/MCHMs/WPU/PVA foam material with porous structure was prepared by freeze-drying method,and 20wt%MWCNT,40wt%MWCNT,40wt%MWCNT/10wt%MCHMs were used as conductive fillers.The effects of filler content,filler type and density on electrical conductivity,electromagnetic shielding performance and mechanical properties are studied.The composite material with a density of 232.8042 mg/cm³ and 40wt% MWCNT has a conductivity of 30.2 S/m and an electromagnetic shielding efficiency of 23 dB.After adding 10wt%MCHMs,the composite material achieved a conductivity of 33.2 S/m and an electromagnetic shielding effectiveness of 28 dB.Both absorption losses accounted for 70%.It can be seen that increasing the content of MWCNT,increasing the density of the composite material,and the introduction of MCHMs all have a positive effect on the electrical conductivity and electromagnetic shielding performance of the composite material.MCHMs,MWCNT/MCHMs/WPU,MWCNT/MCHMs/WPU/PVA,as one-dimensional,two-dimensional,and three-dimensional electromagnetic shielding materials,can be respectively applied to electromagnetic shielding materials such as fillers,coating materials,and fillers.