Preparation Of PANI/PVDF-Based Dielectric Composites And Research On Their Performance

In this thesis, several PVDF-based dielectric composite with high dielectric constant and low dielectric loss were prepared via introducing nano PANI with good compatibility and polarizing capability as well as BT@PANI and Ag@PANI functional filler prepared via nano-compounding technology. On the basis of effective improvement of their dielectric constant, their dielectric loss were controlled in lower level, and the good stability of frequency and temperature can also be given. This study focuses on the influence of interface and microstructure on the dielectric constant in the composite. The physical mechanism of the dielectric composite were analyzed combining the dielectric physics theory.The main contents and results of this thesis were as follows:(1) Using PANI nanoparticles synthesized through ice-freezing method with good dispersibility as filler, PANI/PVDF dielectric composites were prepared by means of solution blending. The results showed that PANI nanoparticles with diameter of 30 nm were synthesized. Nanocomposites with 10 wt% loading of PANI possessed the dielectric loss at only about 0.06 and high dielectric permittivity up to35 at 1 kHz, the composites also showed good frequency and temperature stability.The dielectric constant were highly enhanced but the dielectric loss have no significant change. The excellent dielectric properties should be ascribed to the improvement in the polarization ability as well as the transformation from of PVDF crystaline.(2) BT/PANI/PVDF three-phase composite dielectrics were prepared by introducing BT with high dielectric constant into PANI/PVDF matrix. Results showed that the three-phase composites presented the dielectric constant of 49 and dielectric loss of 0.12 with 30 wt % loading of h-BT at 1 kHz which was superior to BT/PVDF composite. The dielectric constant of BT/PANI/PVDF composite significantly improved compared to that of BT/PVDF composite, the composites also showed excellent frequency and temperature stability. The introduction of PANI reduced the dielectric constant and improved dielectric compatibility between ceramic particles and polymer matrix which enhanced the dielectric constant of the composite.(3) The core-shell(BT@PANI) compounds were prepared by the introduction of PAA onto the surface of BT via in situ polymerization. Using core-shell BT@PANI compounds as filler, the BT@PANI/PVDF three-phase composites were prepared.The results showed that percolation threshold of the three-phase composite presented at 30 wt% filler loading and its dielectric constant reach to 250 which was 30 timeshigher than PVDF matrix at the same condition. The three-phase composites presented the dielectric constant of 80 and dielectric loss of 0.79 only the filler loading was 20 wt% at 1 kHz. This three-phase composite achieved the balance of high dielectric constant, low dielectric loss and filler loading. The excellent dielectric properties were attribute to good interface combination between BT@PANI and PVDF.(4) Ag@PANI composite fiber were prepared by solution polymerization and interfacial polymerization. Using core-shell Ag@PANI compounds as filler, the Ag@PANI/PVDF dielectric composites were prepared. Results showed that the composite filled with Ag@PANI prepared by solution polymerization showed better dielectric performance. The composites presented the dielectric constant of 55 and dielectric loss of 0.85 only the filler loading was 10 wt% at 1 kHz. The excellent dielectric properties were attribute to the micro capacitance function of Ag@PANI and interfacial polarization of PVDF matrix.