Preparation And Properties Study Of All Organic PVDF-based Dielectric Composites

In this paper,the polymer dielectric material PVDF was used as matrix;the poly(styrene-block-maleic anhydride)(PS-b-MAH)and poly(styrene-block-methyl methacrylate)(PS-b-PMMA)with-C=O groups which had good compatibility with PVDF were selected as organic fillers to prepare all organic dielectric composites for enhanced dielectric and energy storage properties.The effects of filler type,content and molecular weight on the energy storage properties were investigated,and the mechanism of performances improvement was explained.Firstly,the heat treatment conditions of single-phase PVDF films prepared by solution casting method were studied for determining the preparation process of composites.The heat treatment conditions were optimized,which affected the breakdown strength(Eb)and dielectric constant(?r)of PVDF.The results showed that when quenching temperature,quenching time,annealing temperature and annealing time were 200?,30 min,110??and 12 h,the better Eb and ?r the of the gained PVDF were 361 kV/mm and 10.8,which were 1.17 and 1.26 times higher than that of untreated PVDF,respectively.The effect of PS-b-MAH with different content and molecular weight on dielectric and energy storage properties of composites was investigated by single factor test.It was found that when the mol%of MAH in PS-b-MAH increased from 20%to 44%,the energy density Uc of the composites increased with the increase of the MAH content.When the content of PS-b-MAH(MAH mol%=44%)was 3 wt%,the maximum Eb and Uc of the composites were 415 kV/mm and 8.4 J/cm3,which were 1.15 and 1.35 times higher than that of pure PVDF,respectively.The improvement of energy storage properties were mainly attributed to the good compatibility induced by the the intermolecular interactions between O atom of-C=O in PS-b-MAH and H atom of-CH2-in PVDF.The effect of PS-b-PMMA with different content on the dielectric and energy storage properties of composites was investigated.It was found that when the content of PS-b-PMMA was 9 wt%,the composites exhibited the largest Eb of 522 kV/mm and discharged energy density(Ue)of 10.1 J/cm3,which were 1.45 and 2.5 times higher than that of pure PVDF,respectively.The energy storage properties of PS-b-PMMA/PVDF composites were also superior to that of PS-b-MAH/PVDF composites.As the PS-b-PMMA content increased from 0 wt%to 12 wt%,the charged-discharged efficiency(?)of the composites increased gradually,and when the PS-b-PMMA content was 12 wt%,at 300 kV/mm,the ? of PS-b-PMMA/PVDF composites was 88%,which was 1.35 times higher that of PVDF.The increase of the discharged energy density may be due to the reduced the residual polarization of PVDF with the introduction of PS-b-PMMA.