Preparation And Properties Of Graphene/BMI High-dielectric-constant Material

With the rapid development of electronic industry, high dielectric constant composite, which has good abilities of uniforming electric field and storing electricity, shows great prospect in terms of memory, capacitors, and all kinds of sensors. Compared with traditional inorganic high dielectric materials, high dielectric polymer matrix composites, which combine the advantages of polymer materials and inorganic materials, have excellent dielectric properties, mechanical properties, heat resistance, molding technology and so on. Among them, the conductor/polymer composites have a very high dielectric constant due to seepage effect. Therefore, developing more excellent conductor/polymer dielectric materials has become a hot and key point in the research of engineering dielectric materials.The research targets and pilot program of this project are determined based upon literature search, and the research works are carried out as follows. Firstly, graphene(rGO) was prepared by chemical reduction method and studied focuses on the degree of reduction and dispersion of graphene. The results showed that graphene had removed most of the oxygen-containing functional groups after reduction, C/O ratio of 3.89. Graphene had excellent dispersibility in water and some organic solvents. Secondly, aromatic hyperbranched polyester(HBPE) was used to tough bismaleimide(BMI) and the effect of the addition of HBPE on mechanical properties, heat resistance, dielectric properties and microstructure morphology were studied. The results showed that the addition of HBPE can significantly improve the mechanical property of BMI/BA resin. By using 15wt% HBPE, impact strength, bending strength and tensile srength respectively increased 36.3%, 43% and 22.8% compared with untreated BMI/BA resin. SEM results showed that the addition of HBPE led to macroscopic homogeneous and microscopic phase separation structure. According to thermal analysis, the addition of HBPE improved obviously the heat resistance of materials. By using 15wt% HBPE, the glass transition temperature and the initial decomposition temperature increased 10 oC and 23 oC compared to the BMI/BA resin. Dielectric analysis showed that HBPE/BMI/BA resin had higher dielectric constant and dielectric loss compared to BMI/BA resin. Lastly, rGO/modified BMI composites were prepared by ultrasonic dispersion- situ polymerization and the effect of the addition of rGO on mechanical properties, heat resistance, dielectric properties and microstructure morphology were studied. The results showed that the addition of graphene can further improve the toughness and strength of the composites. By using 1wt% rGO, impact strength, bending strength and tensile srength respectively increased 17.9%, 7.9% and 12% compared with modified BMI. Thermal analysis showed that heat resistance was roughly equal with modified BMI. Dielectric analysis results showed that rGO/modified BMI composites had good dielectric properties. At the frequency of 1 kHz, by using 2wt% rGO, the dielectric constant of composites jumped to 303.5, which was about 70 times of the matrix resin. At the same time, the composites also had low dielectric loss(0.13) and good frequency stability.