Preparation Of Graphene/Polymer Composites And The Study Of Their Dielectrical And Thermally Conductive Properties

With the the rapid development toward miniaturization and multi-function of theelectronic devices, the electronic industry urgently needs higher dielectric and higherthermally conductive polymer material in order to reduce the volume of electroniccapacitors and improve the heat dissipation capacity of the electronic device.Adding high dielectric ceramic fillers and electrically conductive fillers into thepolymer matrix can be two effective ways to improve the permittivity of polymermaterials. As fabricating electrically conductive fillers/polymer composites canimprove the dielectric constant significantly with a low volumn constant, this wayshows great advantages in improving the permittivity of polymer materials. But it canresult higher dielectric loss at the same time. The first part of this thesis makes useof the high electrically conductivity of graphene and fabricates a specially kind ofgraphene filler （rPANI-GS-rPANI） with “insulator-conductor-insulator” sandwichstructure. When adding this kind of filler into the Poly （methyl methacrylate）（PMMA）, the dielectric constant of the polymer composites is rised with the thefiller’s content and the dielectric loss still remains quite low. For example, when thegraphene volumn percentage reaches6%, the dielectric constant of the materialincreases to40.6from3.6, while the dielectric loss is as low as0.12.Meanwhile, adding fillers with high thermal conductivity into polymer matrix canalso improve the thermally conductive property. Ceramic, metal and carbon-basedmaterials are the concentional fillers to improve the thermally conductive propertiesof polymer materials. Carbon-based fillers, especially graphene, have geat merits inthe field of improve the thermal conductivity of polymer matrix beause of their outstanding properties, such as ultral-high thermal conductive, large specific surfacearea and low density. The second part of this thesis mainly introduces the way tofabricate graphene/polymer composites and study the thermally conductiveenhancement of the polymer matrix. This kind of graphene fillers are produced bysolvent liquid exfoliation of graphite with the help of intercalation of POSS. Researchshows that the graphene flakes prepared by this method （PGGF） can improve thethermal conductivity of the polymer matrix more effectively in compared with theones produced without POSS （EG）. When the volume percentage of PGGF fillersreaches15%, the thermal conductivity of the composites is increased to1.7Wm^-1K^-1from0.24Wm^-1K^-1, which is nearly an enhancement of six-times.These results show that the two dimensional nanosheet of graphene can be apromising kind of filler for preparing a high dielectric and high thermal conductivitypolymer composite.