Research On Low Reflection Electromagnetic Shielding Rubber Composite

With the development of electronic information technology,the application of electromagnetic wave in daily life is more and more widely,which brings convenience to people,but also causes serious electromagnetic pollution,so it needs to be controlled by electromagnetic shielding materials.As a kind of flexible material,electromagnetic shielding rubber composite can overcome the disadvantages of traditional electromagnetic shielding materials,such as high density,difficult processing and easy corrosion.It is a new development direction of electromagnetic shielding materials in the future.In this paper,multi-walled carbon nanotubes(MWCNT)were used as functional fillers to prepare VMQ/MWCNT composite electromagnetic shielding materials and NBR/EPDM/MWCNT composite microwave absorbing materials.The low reflection electromagnetic shielding rubber composites were prepared by combining the two materials in different ways,and the electromagnetic shielding properties of the three composites were studied.The effects of MWCNT content and curing method on VMQ/MWCNT composites were studied.It is found that the addition of MWCNT can improve other properties except elongation at break.When the MWCNT content reaches 8 phr,the composite has the best electromagnetic shielding effectiveness.After post cure,the physical and mechanical properties of the material tend to be stable,but the crosslinking density decreases at high MWCNT content(6-8 phr),and the total electromagnetic shielding effectiveness is significantly improved,up to 57.7%.The effect of post cure time on the electromagnetic shielding effectiveness of the composites was studied.It was found that the set of the composites increased significantly at 0-1 h,and reached the maximum at 4 h.The experimental results show that VMQ/MWCNT is a kind of electromagnetic shielding composite with reflection as the main component.The effects of MWCNT content and curing system on the properties of NBR/EPDM/MWCNT composites were studied.It was found that with the increase of MWCNT content,the physical and mechanical properties of the composites did not change significantly,and the real and imaginary parts of the complex permittivity of the composites increased significantly.When the content of MWCNT is 8 phr,the lowest RL_min of the composite is-48.1 d B.The effects of two processing technologies on the dispersion of fillers were studied.It was found that the microwave absorbing properties of the composites were improved by adding MWCNT after inorganic fillers and plasticizers.The effects of double-layer and multi-layer gradient structures on electromagnetic shielding of rubber composites were studied by integrating the above electromagnetic shielding materials and absorbing materials.It was found that the double-layer electromagnetic shielding composites with absorbing layer in the incident direction of electromagnetic wave could effectively reduce the reflection of electromagnetic wave,and the structure with MWCNT content gradient could further reduce the reflection.