聚偏氟乙烯共混物结构调控与储能特性

发布时间：2018-05-04 08:33

本文选题：熔融共混 + 相转变　；参考：《东华理工大学》2017年硕士论文

【摘要】：随着电力行业的飞速发展,电介质电容器具有快速充放电能力和高功率密度的优点而受到广泛关注。与商用储能电容器的介质材料双向拉伸聚丙烯(BOPP)相比,聚偏氟乙烯(PVDF)有着更大的电位移,使其储能密度得到提升,在电介质储能领域有着巨大的研究价值。PVDF的性能与其结构密切相关,比如晶型,故而研究PVDF的晶型转变是非常必要的。本文主要通过熔融共混和流延的方法制备了PVDF共混物,研究了PVDF在共混物中的晶型、温度以及取向对共混物能量储存行为的影响。(1)研究了PVDF/PA6共混物的流变行为,力学行为以及在拉伸作用下PVDF在共混物中的晶型转变。由于PA6微粒的形态和PVDF基体的相互作用,共混物熔体的弹性和粘性可以得到显著加强。在低频下,PA6含量较高时,共混物展现出了近固态熔体行为。受到应力集中的影响,PA6微粒的存在会降低流动应力,从而在机械拉伸作用下抑制α→β相的转变。(2)研究了PVDF/PMMA共混物的结构转变和温度对共混物的能量储存行为的影响。共混物随着PMMA含量的增加,其熔点、结晶温度和结晶度都是下降的;PMMA的加入有利于共混物中α→β相的转变,当PMMA含量达到30wt%时,共混物中β相占据主导地位。随着共混物中PMMA含量的增加,共混物β相的相对含量也是增加的,介电常数、储能密度却是是减小的。随着温度的升高,共混物的介电常数和储能密度都是增加的,其能量效率是减小的。(3)研究了取向对PVDF/PMMA共混物结构转变和能量储存行为的影响。取向对于共混物的结晶度有一定的提高,并且对于PVDFβ相形成有促进作用。PMMA含量在30wt%时,β相相对含量达到90%以上。由于取向对于共混物的总有效偶极矩影响不大,其介电常数与未取向共混物相差无几;但是取向对于共混物的击穿强度由150MV/m提高至200MV/m,从而极化强度增加,储能密度增加。
[Abstract]:With the rapid development of power industry, dielectric capacitors have been paid more and more attention because of their rapid charge-discharge capacity and high power density. Compared with commercial dielectric materials such as biaxial tensile polypropylene (BOPP), PVDF (polyvinylidene fluoride) has a larger electric displacement, which increases its energy storage density. PVDF has great research value in the field of dielectric energy storage. The properties of PVDF are closely related to its structure, such as crystal form, so it is very necessary to study the crystal transformation of PVDF. In this paper, PVDF blends were prepared by melt blending method. The effects of crystal type, temperature and orientation of PVDF on the energy storage behavior of PVDF/PA6 blends were studied. The rheological behavior of PVDF/PA6 blends was studied. Mechanical behavior and crystalline transformation of PVDF in blends under tensile action. Because of the interaction between the morphology of PA6 particles and the PVDF matrix, the elasticity and viscosity of the blend melt can be significantly strengthened. When the content of PA6 was high at low frequency, the blend exhibited near solid melt behavior. Under the influence of stress concentration, the presence of PA6 particles can reduce the flow stress, and thus inhibit the 伪-尾 phase transition under mechanical tension.) the structural transformation of PVDF/PMMA blends and the effect of temperature on the energy storage behavior of the blends were studied. With the increase of PMMA content, the melting point, crystallization temperature and crystallinity of the blends are all decreased, and the addition of PMA is favorable to the transformation of 伪-尾 phase in the blends. When the content of PMMA reaches 30 wt%, the 尾 phase occupies the dominant position in the blends. With the increase of PMMA content in the blends, the relative content of 尾 phase increases, but the dielectric constant and energy storage density decrease. With the increase of temperature, the dielectric constant and energy storage density of PVDF/PMMA blends increased, and their energy efficiency was reduced. The effect of orientation on the structural transformation and energy storage behavior of PVDF/PMMA blends was studied. The orientation increased the crystallinity of the blend to some extent, and promoted the formation of PVDF 尾 phase. When the content of PMMA was 30 wt%, the relative content of 尾 phase was more than 90%. Because the orientation has little effect on the total effective dipole moment of the blends, the dielectric constant of the blends is similar to that of the non-oriented blends, but the breakdown strength of the oriented blends increases from 150MV/m to 200MV / m, thus the polarization strength increases and the energy storage density increases.
【学位授予单位】：东华理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O632.21;TB332

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