Preparation And Study Of Fluoropolymer-based Dielectric Composites

With the advancement of high integration and miniaturization of electronic components,it is crucial to control the synthesis and processing performance of the materials at the nanoscale,which raises a higher demand to the performance of dielectric materials.The traditional single dielectric material is far from meeting the current market demand.Therefore,the research and preparation of polymer matrix composites with high dielectric properties and mechanical flexibility are of great significance to the modern electronic equipment and electrical systems.In this paper,polymer matrix composites with high performance are prepared via solution co-blending method,where polyvinylidene fluoride-chlorotrifluoroethylene?P?VDF-CTFE??is used as a flexible substrate and barium titanate is used as a high-dielectric filling phase.High-performance polymer matrix composites are prepared by means of filler surface modification and morphological changes.Moreover,the properties of the polymer matrix composites can be improved by the surface modification and morphology change of fillers.The main contents are as follows:?1?Poly?dodecylfluoroheptyl methacrylate?terminated with thiol end groups?PDFMA-SH?was synthesized through reversible addition-fragmentation chain transfer?RAFT?polymerization and subsequent ammonolysis reaction.Then the fluoropolymer was grafted to the surface of BaTiO₃?BT?nanoparticles by the“thiol-ene”click reaction.A new nanocomposite composed of core-shell PDFMA@BT hybrid nanoparticles and P?VDF-CTFE?matrix was prepared.The effects of fluoropolymer shell on filler dispersion,compatibility between filler and polymer matrix,dielectric properties and breakdown strength were studied in detail.The results show that the strong interfacial adhesion between the hybrid nanoparticles and the P?VDF-CTFE?matrix makes the filler dispersed more evenly in the polymer matrix.Moreover,the excellent compatibility between the filler and polymer matrix improves the breakdown strength of the composite material and inhibits the dielectric loss.?2?Barium titanate nanofiber?BT NF?with high aspect ratio was prepared by electrospinning.In order to further improve the breakdown strength of the composite material,the SiO₂-coated SO@BT NF core-shell type filler was prepared by the St?ber method,and nano-composites with different types of filler were prepared by solution blending and casting methods.The influence of filler morphology and inorganic interface on the dielectric properties and breakdown strength of composite materials were studied,and the change of inorganic nanofiller morphology has a significant effect on improving the dielectric properties of composite materials.When the filler loading is 10 vol%,the dielectric constant of SO@BT NF/P?VDF-CTFE?nanocomposite membrane is 35.62,while BT NP/P?VDF-CTFE?is 19.42,which is raised 2 times.Besides,the addition of low-content nanofibers has enhanced the breakdown strength of the composite material benefited by the anisotropy of nanofibers,and the improvement of the breakdown strength is more remarkable after the coating of SiO2 on the surface of BT NF.Compared with unmodified BT NF,the introduction of SiO₂ coating has greatly improved the breakdown strength and dielectric loss of nanocomposites.