Preparation Of Carbon Nanomaterials/Epoxy Composites And Their Electromagnetic Interference Shielding And Mechanical Properties

Since information technological revolution, electronic equipments and products have emerged in endlessly, and are used by more and more people. However, it can lead to more and more electromagnetic wave around people, and gradually harm to people’s health. Nowadays, the negative effects bring by electromagnetic wave are so large that people start to pay attention on it. Therefore, the research about electromagnetic interference (EMI) shielding materials have became more and more. In this paper, on the one hand, we use electrically conductive graphene and magnetic carbonyl iron as fillers, which can attenuate electromagnetic wave by dielectric loss and magnetic loss, to prepare the composites with excellent EMI shielding performance. Meanwhile, we also use conductive filler, such as carbon nanotube and graphene, to prepare the preforms with the three-dimensional structure and then use them as filler, and utilize the three-dimensional structure of them to make the composites possess both excellent EMI shielding performance and mechanical properties with the ultra-low filler content. The main work were as follow:1, we use thermally reduced graphene oxide (TGO) as conductive filler, carbonyl iron (CI) as magnetic filler and epoxy as matrix to prepare composites. The results show that the electrical conductivity and EMI shielding performance of the composites prepared by different stirring method (centrifugal mixing, ultrasonic mixing and mechanical mixing) exist the obvious differences. The addition of TGO can not only build an interconnected conducting network within composites, but also prevent the aggregation and sedimentation of CI components and make it disperses in the composites uniformly. The incorporation of CI components leads to an effective increment in magnetic properties, permeability and magnetic loss of the composites, and then lead to the further enhancement in the EMI shielding performance of the composites. Compare with epoxy/TGO (3 wt%) composite (-20 dB), EMI shielding performance of epoxy/TGO (3 wt%)/CI (30 wt%) composites have a different increment by the addition of CI with different shape. Therein, epoxy/TGO (3 wt%)/CI (30 wt%) composite filled with spherical CI particles possess the best EMI shielding performance (average EMI shielding effectiveness is 36 dB, the maximum can reach 40 dB).2, we use resol and graphene oxide as raw materials to prepare phenolic resin-modified graphene aerogel (p-GA) with the three-dimensional structure by hydrothermal method. Then, it is used to prepare epoxy/p-GA composites by adopting a vacuum-assisted method. The results show that the three-dimensional structure of p-GA become more complete and firm by the addition of resol. Scanning electron microscope (SEM) images and transmission electron microscope (TEM) images show that p-GA can maintain the three-dimensional structure before and after the preparation process. The higher annealed temperature can lead to higher intrinsic electrical conductivity, lower aerogel density and lower filler content in composites of p-GA, and then lead to higher electrical conductivity and EMI shielding performance of the epoxy/p-GA composites. With only 0.33 wt% of filler content, epoxy/p-GA-1300 composite exhibits a high electrical conductivity of 73 S·m-1 and an excellent EMI shielding effectiveness of 35 dB. Moreover, with the increase content of resol, the three-dimensional structure of p-GA become more and more complete and firm, and flexural property of the corresponding composites can also be improved. Flexural strength and flexural modulus of epoxy composite filled with p-GA (1:30), which is prepared by 30 mg·ml-1 resol and 1 mg·ml-1 graphene oxide, increased by 67% and 20% respectively compared to epoxy.3, we use carbon nanotube sponge (CNT sponge) with three-dimensional structure as filler to prepare epoxy/CNT sponge composites by using a vacuum-assisted method. SEM images show that CNT sponge possess a good three-dimensional structure, and the CNTs within it can disperse uniformly in epoxy matrix. When the content of CNT sponge was only 0.66 wt%, the corresponding composites can obtain a remarkable conductivity of 148 S·m-1, an outstanding EMI shielding effectiveness of around 33 dB with 2 mm sample thickness and an excellent mechanical properties. Compared with epoxy, flexural strength, flexural modulus, tensile strength, tensile toughness and elongation at break of epoxy/CNT sponge (0.66 wt%) composite increased by 102%,27%,64%,250% and 97% respectively.