摘要/Abstract
拥有超快放电速率以及超高功率密度的聚合物薄膜电容器, 在脉冲功率技术、先进电力与电子系统等诸多领域中发挥着关键的作用. 本工作采用溶液刮涂的方法, 制备了柔性全有机热塑性聚氨酯/聚偏氟乙烯-六氟丙烯(TPU/P(VDF-HFP))复合薄膜, 并结合多种表征手段系统地研究了复合薄膜的微观特性、介电特性、绝缘特性、储能特性以及力学性能. 系统观察和测试结果表明: 适量热塑性聚氨酯添加到P(VDF-HFP)中, 能够形成分散性和相容性均十分优异的两相交联结构, 从而进一步提高复合材料的电学、储能、力学等性能. 在P(VDF-HFP)中添加2% (φ) TPU时, 复合薄膜的特征击穿强度为450 MV/m, 对应的放电能量密度为7.03 J/cm3, 分别提高了25.35%和49%. 此外, 复合材料的机械性能也随着TPU的添加得到一定程度的提高, TPU-2% (φ)/P(VDF-HFP)复合薄膜的杨氏模量、抗拉强度以及断裂伸长率分别达到591.22 MPa, 25.6 MPa, 362%. 通过以上表征分析, 发现在聚合物中添加弹性体橡胶能够形成具有高击穿强度、高能量密度以及高充放电效率等优点的柔性电介质材料, 有望在大规模的工业生产中获得较好的应用.
关键词: 电介质, P(VDF-HFP), 全有机聚合物, 击穿强度, 能量密度, 薄膜电容器
Polymer-based film capacitors with ultra-fast discharge rate and high-power density play a key role in many fields, such as pulsed power technology, advanced electric and electronic systems. In this paper, the flexible all-organic composite films with thermoplastic polyurethanes (TPU) and poly(vinylidene fluoride-co-hexafluoropropene) (P(VDF-HFP)) are prepared by a solution coating method, combined with a variety of characterization methods to systematically study the microscopic properties, dielectric properties, insulation properties, energy storage properties and mechanical properties of the composite films. The typical experimental procedure for the fabrication of all-organic composite films is as follows: First, the TPU and P(VDF-HFP) pellets were dried in the oven for 24 h. Then, 1 g P(VDF-HFP) and corresponding TPU (0, 1% (φ), 2% (φ), 3% (φ), 4% (φ), 5% (φ)) were added into 10 mL N,N-dimethylformamide (DMF) solution, and were stirred vigorously at room temperature for 24 h. The mixtures were moved into vacuum oven for 30 min to eliminate the air. The solutions were cast onto a clean glass, and finally were dried at 70 ℃ for 12 h to obtain the TPU/P(VDF-HFP) films. Systematic observation and tested results show that: adding an appropriate amount of thermoplastic polyurethane to P(VDF-HFP) can form a two-phase cross-linked structure with excellent dispersibility and compatibility, thereby further improving the electrical, energy storage, and mechanical properties of the composite films. In TPU/P(VDF-HFP) composite film with 2% (φ) TPU, the characteristic breakdown strength of the composite film is 450 MV/m, and the corresponding discharge energy density is 7.03 J/cm3, which are increased by 25.35% and 49% compared to the pristine film, respectively. Moreover, the mechanical properties of the composite films have been improved to a certain extent owing to the addition of TPU, and the Young's modulus, tensile strength and elongation at break of the TPU-2% (φ)/P(VDF-HFP) composite film reaches 591.22 MPa, 25.6 MPa, and 362%, respectively. Through the above characterization and analysis, it can be found that adding elastomer rubber to the ferroelectric polymers can form flexible dielectric materials with high breakdown strength, high energy density as well as high charge-discharge efficiency, which is expected to have better applications in large-scale industrial production for film capacitors.
Key words: dielectrics, P(VDF-HFP), all-organic composite, breakdown strength, energy density, film capacitor
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