| Multi-walled Carbon Nanotubes (MWCNT) having a large aspect ratio and high conductivity, making it more suitable fillers for high dielectric composite material. However, according to percolation theory, when the MWCNT content close to the percolation threshold (fc), the composites obtain a higher dielectric constant, while the insulator transition the conductor will lead to a higher dielectric loss. Researchers use coated method to prepared composites, which greatly reducing the dielectric loss. However, these methods are often limited due to the preparation process was more complex, it limiting its application in electronic devices. Therefore, we expect to use a simple method to design and optimization structure, and explore The structure-property relationship in the composite system. The main content and result of this thesis were listed as follow:First, we prepare MWCNT/PVDF through a solution mixing and injection molding method. The effects of the injection molding process on properties of the MWCNT/PVDF composites were studied. The results showed that MWCNT uniformly dispersed in the PVDF matrix through the solution mixing, and the injection molded method can make MWCNT produce orientation and widen the typically narrow concentration window near the percolation threshold, which is used to dominate the dielectric properties. The electrical percolation threshold of MWCNT/PVDF composites is 5.00 wt.%-9.00 wt.% based on percolation theory. The permittivity of 5.00 wt.% MWCNT/PVDF,7.00 wt.% MWCNT/PVDF and 9.00 wt.% MWCNT/PVDF composites were 23.8,48.71 and 73.55, then loss angle were 0.11,1.96 and 4.79 at 100Hz, respectively.Second, we also prepare g-MWCNT/PVDF and CTAB@g-MWCNT/PVDF through a solution mixing and injection molding method. The properties of the two kinds of composites were studied. The results showed that the percolation threshold of g-MWCNT/PVDF composites decreased to 3.00 wt%-5.00 wt% through graphitizing. When the frequency is 100Hz, the dielectric constant of 5.00 wt% g-MWCNT/PVDF composites creased from 23.8 to 105 at 100Hz,, but loss angle creased from 0.11 to 8.67. After adding CTAB, The dielectric constant of 5.00 wt% CTAB@g-MWCNT composite creased to 119, and the loss angle only were 0.816. |
