Semicrystalline Structure Dielectric Property Relationship and Electrical Conduction in a Biaxially Oriented Poly(vinylidene fluoride) Film under High Electric Fields and High Temperatures
Semicrystalline Structure Dielectric Property Relationship and Electrical Conduction in a Biaxially Oriented Poly(vinylidene fluoride) Film under High Electric Fields and High Temperatures
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DOI：
10.1021/acsami.5b02944
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发表时间：
2015-09-16
影响因子：
9.5
通讯作者：
Zhu, Lei
中科院分区：
文献类型：
--
作者：
Yang, Lianyun;Ho, Janet;Zhu, Lei
聚偏二氟乙烯 (PVDF) 基均聚物和共聚物由于其高介电常数而对广泛的电活性应用具有吸引力。特别是，双向拉伸PVDF(BOPVDF)薄膜表现出与双向拉伸聚丙烯薄膜一样高的直流击穿强度。在这项工作中，我们通过研究商用 BOPVDF 薄膜揭示了高介电常数的分子起源。通过测定 BOPVDF 中非晶相的介电常数，可以得出约 100% 的高值。在25℃下获得了图21-22，并提出了三相（即层状晶体/取向中间相/非晶区）半晶模型来解释该结果。同时，通过热刺激去极化电流（TSDC）光谱和漏电流研究研究了高电场和高温下 BOPVDF 的电子传导机制。当 BOPVDF 极化温度高于 75 摄氏度和 20 MV/m 时，金属电极的空间电荷注入被认为是电子传导的主要因素。此外，当使用银或铝作为电极时，在高场作用下电化学反应会产生新的离子。由于PVDF和金属电极之间的电化学反应，在高场和高温条件下使用PVDF及其共聚物的实际电气应用提出了一个问题。本研究提出了一种防止 PVDF 电化学降解的潜在方法。
Poly(vinylidene fluoride) (PVDF)-based homopolymers and copolymers are attractive for a broad range of electroactive applications because of their high dielectric constants. Especially, biaxially oriented PVDF (BOPVDF) films exhibit a DC breakdown strength as high as that for biaxially oriented polypropylene films. In this work, we revealed the molecular origin of the high dielectric constant via study of a commercial BOPVDF film. By determination of the dielectric constant for the amorphous phase in BOPVDF, a high value of ca. 21-22 at 25 degrees C was obtained, and a three-phase (i.e., lamellar crystal/oriented interphase/amorphous region) semicrystalline model was proposed to explain this result. Meanwhile, electronic conduction mechanisms in BOPVDF under high electric fields and elevated temperatures were investigated by thermally stimulated depolarization current (TSDC) spectroscopy and leakage current studies. Space charge injection from metal electrodes was identified as a major factor for electronic conduction when BOPVDF was poled above 75 degrees C and 20 MV/m. In addition, when silver or aluminum were used as electrodes, new ions were generated from electrochemical reactions under high fields. Due to the electrochemical reactions between PVDF and the metal electrode, a question is raised for practical electrical applications using PVDF and its copolymers under high-field and high-temperature conditions. A potential method to prevent electrochemical degradation of PVDF is proposed in this study.