Study On Preparation And Dielectric Properties Of Polyvinylidene Fluoride Composite Films

In recent years,with the vigorous development of the electronics industry,it is particularly urgent to develop a new generation of flexible dielectric materials with high energy storage and low loss.Polyvinylidene fluoride(PVDF)and its copolymers have attracted great attention due to their high dielectric constant and become the most potential dielectric energy storage material.In this paper,P(VDF-HFP)was used as the matrix material and the core-shell structure M220(shell is polymethyl methacrylate(PMMA),core is polyacrylate)was introduced by solution casting to prepare different ratios of P(VDF-HFP)/M220 composite films,and the effects of M220 on the crystallization behavior and energy storage performance of P(VDF-HFP)were studied.In addition,MWCNTs as conductive fillers also were introduced in this paper.And different ratios of the P(VDF-HFP)/MWCNTs two-phase composite films and P(VDF-HFP)/PMMA/MWCNTs three-phase composite films(the content of PMMA is 10%)were prepared by melt method and solution method.M220 as a heterogeneous nucleating agent to promote crystallization when its content is low,and its structure will rupture and hinder the crystallization when the content of M220 is high.The dielectric constant and dielectric loss of the composites decreased with the addition of M220,but the breakdown strength of the composite films was significantly improved.When the M220 content was 5%,the breakdown strength reached to 464.93 MV/m.Moreover,the discharge efficiency of the composite films was improved.Under the electric field of 100MV/m,the discharge efficiency of the composite film is 78% when the M220 content is 3%,the discharge efficiency of the P(VDF-HFP)film is only 65%.For the P(VDF-HFP)/MWCNTs composite films,the percolation threshold is when the content of carbon nanotubes is 1%.At this time,the dielectric constant of the composite films is reach up to 154,and the dielectric loss is 5.2.In addition,the breakdown strength of composites was significantly reduced,and the tensile properties increased first and then decreased with the increasing of MWCNTs content.When the content of MWCNTs was 1.5%,the tensile strength and elongation at break of the composite films both reached to the highest values,respectively 34 MPa and 717%.For the P(VDF-HFP)/PMMA/MWCNTs composite films,the increasing of MWCNTs content has little effect on the tensile properties,and the dielectric constant and dielectric loss both increased with the increasing of MWCNTs content.When the MWCNTs content is 2%,the dielectric constant of the composite film is as high as 120,the dielectric loss is 11.5,and the breakdown strength of the films fell faster than the two-phase composite film.