| Electromagnetic wave play a useful role in health care, construction, exploration, etc,on the other hand, electromagnetic interference and electromagnetic radiation generated by the electromagnetic waves had a negative impact on the human body and the device.In order to reduce the electromagnetic wave negative effects on the health hazards of equipment, we can use the highly conductive material such as a metal material as an electromagnetic wave shielding material, but due to high density of metallic materials and perishable, in the current aircraft and other military purposes, to cut when they reach a certain shielding effect under heavy resistance to environmental change requirement does not apply. Thus, the composite material can be used controllability can be designed, the design for the special cases apply electromagnetic shielding materials become necessary.In this paper,we've researched the carbon black, graphite as the conductive filler compounding with epoxy, prepared electromagnetic shielding composites.In order to reduce the density of the composites, reinforce the dispersibility of the filler to improve the electromagnetic shielding conductive composites and electromagnetic shielding effectiveness, add lightweight polystyrene microspheres into the carbon black / epoxy and graphite / epoxy composites.The carbon black / polystyrene microsphere / epoxy composites and graphite / polystyrene microsphere / epoxy composites were prepared by mechanical stirring, and studied the electrical properties, dielectric properties and electromagnetic shielding performance of the material.The results are as follows:The introducing of polystyrene microspheres reduces the density of CB/epoxy system, without introducing polystyrene microspheres, the minimum density of the composites is 1.13 g/cm3, the minimum density of the composites is 0.800 g/cm3 when introduced the polystyrene microspheres. The addtion of polystyrene microspheres improved CB/epoxy composite volume conductivity from 1.26×10-4S/cm to 3.30×10-3S/cm at the same carbon black volume fraction of 36.0vol%. The addtion of polystyrene also improved the dielectric properties of the material. The dielectric loss increased from a maximum of 0.480 to 1.46 after adding the microspheres. Within 0.96-1.46 GHz frequency range,the addtion of polystyrene microspheres also improved the electromagnetic shielding effectiveness from 12.2dB to 15.4dB.The increasement of the reflection loss is more than the absorption loss after the addtion of the polystyrene microspheres.As for the Graphite/polystyrene microspheres/epoxy composites, as the proportion of polystyrene microspheres to graphite increases, the density of graphite /polystyrene microspheres/ epoxy composites gradually reduced, by a ratio of 0.0125: 1 of 0.961 g/cm3 down to the ratio of 0.05:1 of 0.617 g/cm3. As the proportion of polystyrene microspheres to graphite gradually increased, its volume resistivity decreased slightly, then slightly increased by a ratio of 0.0125: 1 of 1.00×10-3S/cm down to the ratio of 0.025: 1 of 4.74×10-4S/cm, then slightly up to a ratio of 0.05: 1 of 4.98×10-4S/cm. As the ratio of the polystyrene microsphere and graphite is increased, and the real part of the dielectric constant was decreased as the imaginary part of the dielectric constant also showed a trend of decreasing, the real part of the dielectric constant decreased from the ratio of 0.0125:1 of 9.18 to the ratio of 0.025:1 of 5.80. The imaginary part of the dielectric constant decreased from ratio of 0.0125:1 of 0.78 to the ratio of 0.025:1 of 0.150. The electromagnetic shielding effectiveness decreased with the increasing ratio of the polystyrene microsphere and graphite,then the specific electromagnetic shielding effectiveness of the composites increased with the increasing ratio of the polystyrene microsphere. The reflection loss decreased with the increasing ratio of the polystyrene microsphere and graphite, while the absorption loss decreased. |
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