压电相聚偏氟乙烯（PVDF）的制备与性能研究

发布时间：2018-03-16 18:04

本文选题：聚偏氟乙烯　切入点：剪切力　出处：《江苏科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：聚偏氟乙烯(PVDF)作为一种半结晶多晶型功能高分子材料,至少含有四种不同的晶体结构,即α,β,γ,δ晶相。其中,因为β晶和γ晶都含有TTT全反式构象而表现出优异的铁电和压电性能,而且PVDF具有柔软轻质、频响宽、力电转换灵敏度高、耐冲击等优点,所以PVDF薄膜被广泛应用于电子器件。但是,制备β和γ晶这两种晶相的条件较为苛刻,需要机械拉伸、高温高压、高电场等复杂的实验条件;同时,获得的PVDF薄膜表面粗糙,漏电流较高。所以,设计更简单有效制备高含量β晶和γ晶的实验方法尤为重要。本论文主要采用刀片剪切法和纤维剪切法,制备高含量β晶和γ晶PVDF薄膜。利用广角X-射线衍射仪(WAXD)、傅里叶变换红外光谱(FTIR)和拉曼光谱仪(Raman)定量的研究了不同温度下PVDF剪切膜的β晶和γ晶含量的变化;利用偏光显微镜(POM)和原子力显微镜(AFM)研究了PVDF剪切膜的表面粗糙度和分子链的取向性;利用原位热台和差示扫描量热法(DSC)定性的研究了退火温度温度对PVDF剪切膜的影响;利用压电力显微镜(PFM)和铁电测试系统研究了PVDF剪切膜的电学性能,为其在未来的电子器件中的应用提供有价值的信息。结果表明,当刀片剪切力施加于PVDF熔体膜时会诱导高含量β晶形成,且随着剪切温度的升高,β相的含量逐渐增加,α相含量逐渐较少。此外,PVDF剪切膜表现出较优的取向性,分子链沿着剪切力的方向排列,片晶垂直于剪切力方向;同时,PVDF剪切膜表面非常光滑,β相的含量分布均匀。将PVDF剪切膜置于较高温度下进行原位退火处理,发现剪切膜的β相的含量不发生变化,表明剪切膜晶体结构稳定,退火有益于晶体结构完善而不发生晶体构象的改变。通过拉伸聚酰胺纤维对PVDF熔体施加剪切力,在纤维两侧会形成均匀取向的柱晶结构。在较低温度下,得到的都为α柱晶,将其置于高温下退火,可发生α→γ′的相转变;在较高温度下,随着结晶时间的延长,α柱晶的生长和α→γ′的相转变同时进行。相较于α球晶的相转变,α柱晶的相转变更均匀可控。通过控制温度,在先得到的内层柱晶外侧再制备一层柱晶的体系中,结晶温度和内层柱晶的晶体结构对外层柱晶有不同程度的影响。先低温后高温结晶,内层柱晶的晶体结构对外层柱晶的影响更大;先高温后低温结晶,结晶温度对外层柱晶的影响更大。
[Abstract]:Polyvinylidene fluoride (PVDF), as a semi-crystalline polycrystalline functional polymer, contains at least four different crystal structures, namely 伪, 尾, 纬, 未 crystalline phase, in which both 尾 and 纬 crystals exhibit excellent ferroelectric and piezoelectric properties due to the all-trans conformation of TTT. Moreover, PVDF has the advantages of soft and light weight, wide frequency response, high sensitivity to electromechanical conversion and shock resistance. Therefore, PVDF thin films are widely used in electronic devices. However, the preparation conditions of 尾 and 纬 crystals are harsh and require mechanical stretching. High temperature and high pressure, high electric field and other complicated experimental conditions. At the same time, the surface of the obtained PVDF thin film is rough, the leakage current is high. It is very important to design a simpler and more effective experimental method for preparing high content 尾 -crystal and 纬 -crystal. In this paper, the blade shear method and fiber shearing method are mainly used. High content 尾 -crystalline and 纬 -crystalline PVDF thin films were prepared. The changes of 尾 -crystal and 纬 -crystal content in PVDF shear films at different temperatures were quantitatively studied by means of wide-angle X-ray diffraction (WAXD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy (Raman). The surface roughness and molecular chain orientation of PVDF shear film were studied by polarizing microscope and atomic force microscope (AFM), and the effect of annealing temperature on PVDF shear film was studied qualitatively by in-situ thermostat and differential scanning calorimetry (DSC). The electrical properties of PVDF shearing film were studied by using PPM) and ferroelectric test system, which provided valuable information for its application in electronic devices in the future. The results show that, When the blade shear force is applied to the melt film of PVDF, the high content of 尾 -crystal will be induced, and the content of 尾 -phase will gradually increase and the content of 伪 phase will decrease with the increase of shear temperature. In addition, the shear film of PVDF has a better orientation. The molecular chains are arranged along the direction of shear stress, and the wafer crystal is perpendicular to the direction of shear force. At the same time, the surface of PVDF shear film is very smooth and the content of 尾 phase is uniform. The PVDF shearing film is annealed in situ at a higher temperature. It is found that the content of 尾 phase in the shear film does not change, which indicates that the crystal structure of the shearing film is stable and annealing is beneficial to the perfection of the crystal structure without changing the crystal conformation. The shear force is applied to the melt of PVDF by tensile polyamide fiber. Homogenous columnar structure will be formed on both sides of the fiber. 伪 -columnar crystals can be obtained at lower temperature and annealed at high temperature. 鈫扨hase transition of 纬', growth of 伪 columnar crystal and 伪 with the increase of crystallization time at higher temperature. 鈫扵he phase transition of 纬'is carried out at the same time. Compared with the phase transition of 伪 -spherulite, the phase transition of 伪 -columnar crystal is more uniform and controllable. The crystallization temperature and the crystal structure of the inner columnar crystal have different effects on the outer columnar crystal. The crystal structure of the inner columnar crystal has more influence on the outer columnar crystal, and the crystal structure of the inner columnar crystal has more influence on the outer columnar crystal, the first high temperature then the low temperature crystallization, The effect of crystallization temperature on the outer columnar crystal is greater.
【学位授予单位】：江苏科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB324

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