柔性高储能P(VDF-CTFE)/PA11-g-GMA聚合膜的制备与性能研究

Preparation and Characterization of P(VDF-CTFE) /PA11-g-GMA Flexible Films with High Energy Density

采用反应增容及等温拉伸技术制备了柔性高储能P(VDF-CTFE)/PA11-g-GMA聚合物薄膜.通过XRD、SEM以及电性能测试分析了聚合物薄膜的微观结构与介电性能.结果表明,经GMA接枝改性后的P(VDF-CTFE)/PA11-g-GMA聚合物薄膜两相相容性增加;经外力拉伸后,P(VDF-CTFE)/PA11-g-GMA的分子链在外力作用下被强制解缠,极性基团在外场作用下取向程度增大,增加了结晶结构中β相的含量,有效提高了s-P(VDF-CTFE)/PA11-g-GMA聚合膜的介电性能和储能密度;同时,由于外力协同分子链的运动,聚合物链段运动能力也增大,经过增容改性的聚合物薄膜介电损耗下降.因此制备了一类高储能、低损耗的柔性聚合物薄膜,耐压强度达到275 MV/m,储能密度可达8.09 J/cm3,为轻质、柔性、小型功能器件的发展奠定了基础.

Novel flexible P（VDF-CTFE） /PA11-g-GMA ferroelectric polymer films with high energy density,were prepared via melt extrusion in a twin screw extruder and thermal stretching. The preparation protocol including two steps：（1） as an interface compatilizer,GMA was introduced into nylon11（PA11） for preparing blended films;（2） based on stretch processing,the s-P（VDF-CTFE） /PA11-g-GMA films were obtained. The crystal configuration and micromorphology of the films were characterized by x-ray powder diffraction（ XRD）and scanning electron microscopy（ SEM）. The electric energy storage and discharge behaviors in the films were studied by electric displacement（ D）-electric field（ E） loop measurements. It was found that the interface cohesive ability between P（VDF-CTFE） and PA11 was improved because of the strong polar effect of GMA,which is responsible for the increasing of the dipoles and high polarization under the applied fields,clearly observed in the dielectric spectra of the copolymer films. It is also demonstrated that PVDF segments in uniaxially stretched P（VDF-CTFE） /PA11-g-GMA films form large amount of β-crystal. That is to say,if the crystalline morphology with a high β-crystal content can be further modified to help the discharge process,a polymer capacitor film with high energy densities and low dielectric loss can be achieved. In this paper,the breakdown strength and energy density of the flexible s-P（ VDF-CTFE） /PA11-g-GMA films are 275 MV /m and 8. 09 J /cm3,respectively. It shows a great potential of a new class of polymer films with high energy density for flexible capacitors.