Preparation And Dielectric Property Study Of Large Dielectric Constant Polyvinylidene Fluorine Based Nanocomposites

Polymer materials with high dielectric constant have been widely used in modernpower and electronics industry. Traditional ceramic materials possess a high dielectricconstant, but they also have many disadvantages such as high processing temperaturesand poor toughness. Polymer materials have good process ability and toughness, but alow dielectric constant. The preparation of polymer/nano-filler composites bynanocomposite technology is an important way to get both of the excellentperformance. In this paper, the author use poly vinylidene fluoride (PVDF) as thematrix and graphene as the main filler to prepare a series of composites andinvestigate its dielectric properties, and successfully obtain the ideal composites withhigh dielectric constant and low dielectric loss.Firstly, the author choose barium titanate (BT) and graphene (rGO) as the fillersto prepare PVDF/BT/rGO composites. The mutual electrostatic interactions betweennegatively charged graphene oxide and positively charged barium titanate can makethe two species get gather, which has been confirmed in the transmission electronmicroscopy (TEM).The result shows that the dielectric constant of PVDF/BT(40vol%)/rGOcomposites increase with rGO content. When the rGO content is up to0.7%, thesystem reaches percolation. Then the dielectric constant of the composite start todecrease. It is worth noting that when the rGO content is0.6%, the dielectric constantof the PVDF/BT/rGO composites is nearly twice that of PVDF/BT composites whiledielectric loss almost did not change. After variable temperature dielectric testing ithas been found that the dielectric constant of the PVDF/BT/rGO is deeply influencedby the temperature and frequency, showing a very high dielectric constant at high temperature and low frequency.In the end, the author graft methacrylic acid methyl ester (MMA) to the surfaceof grapheme by ATRP method to obtain a modified graphene (GS-PMMA). Afteradding the modified graphene to the PVDF matrix, the dielectric constant ofPVDF/GS-PMMA composite also increase. The PVDF/GS-PMMA start percolationwhen GS-PMMA content is up to3%.