本文選題：聚偏氟乙烯　切入點(diǎn)：剪切力　出處：《江蘇科技大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：聚偏氟乙烯(PVDF)作為一種半結(jié)晶多晶型功能高分子材料,至少含有四種不同的晶體結(jié)構(gòu),即α,β,γ,δ晶相。其中,因?yàn)棣戮Ш挺镁Ф己蠺TT全反式構(gòu)象而表現(xiàn)出優(yōu)異的鐵電和壓電性能,而且PVDF具有柔軟輕質(zhì)、頻響寬、力電轉(zhuǎn)換靈敏度高、耐沖擊等優(yōu)點(diǎn),所以PVDF薄膜被廣泛應(yīng)用于電子器件。但是,制備β和γ晶這兩種晶相的條件較為苛刻,需要機(jī)械拉伸、高溫高壓、高電場(chǎng)等復(fù)雜的實(shí)驗(yàn)條件;同時(shí),獲得的PVDF薄膜表面粗糙,漏電流較高。所以,設(shè)計(jì)更簡(jiǎn)單有效制備高含量β晶和γ晶的實(shí)驗(yàn)方法尤為重要。本論文主要采用刀片剪切法和纖維剪切法,制備高含量β晶和γ晶PVDF薄膜。利用廣角X-射線衍射儀(WAXD)、傅里葉變換紅外光譜(FTIR)和拉曼光譜儀(Raman)定量的研究了不同溫度下PVDF剪切膜的β晶和γ晶含量的變化;利用偏光顯微鏡(POM)和原子力顯微鏡(AFM)研究了PVDF剪切膜的表面粗糙度和分子鏈的取向性;利用原位熱臺(tái)和差示掃描量熱法(DSC)定性的研究了退火溫度溫度對(duì)PVDF剪切膜的影響;利用壓電力顯微鏡(PFM)和鐵電測(cè)試系統(tǒng)研究了PVDF剪切膜的電學(xué)性能,為其在未來(lái)的電子器件中的應(yīng)用提供有價(jià)值的信息。結(jié)果表明,當(dāng)?shù)镀羟辛κ┘佑赑VDF熔體膜時(shí)會(huì)誘導(dǎo)高含量β晶形成,且隨著剪切溫度的升高,β相的含量逐漸增加,α相含量逐漸較少。此外,PVDF剪切膜表現(xiàn)出較優(yōu)的取向性,分子鏈沿著剪切力的方向排列,片晶垂直于剪切力方向;同時(shí),PVDF剪切膜表面非常光滑,β相的含量分布均勻。將PVDF剪切膜置于較高溫度下進(jìn)行原位退火處理,發(fā)現(xiàn)剪切膜的β相的含量不發(fā)生變化,表明剪切膜晶體結(jié)構(gòu)穩(wěn)定,退火有益于晶體結(jié)構(gòu)完善而不發(fā)生晶體構(gòu)象的改變。通過(guò)拉伸聚酰胺纖維對(duì)PVDF熔體施加剪切力,在纖維兩側(cè)會(huì)形成均勻取向的柱晶結(jié)構(gòu)。在較低溫度下,得到的都為α柱晶,將其置于高溫下退火,可發(fā)生α→γ′的相轉(zhuǎn)變;在較高溫度下,隨著結(jié)晶時(shí)間的延長(zhǎng),α柱晶的生長(zhǎng)和α→γ′的相轉(zhuǎn)變同時(shí)進(jìn)行。相較于α球晶的相轉(zhuǎn)變,α柱晶的相轉(zhuǎn)變更均勻可控。通過(guò)控制溫度,在先得到的內(nèi)層柱晶外側(cè)再制備一層柱晶的體系中,結(jié)晶溫度和內(nèi)層柱晶的晶體結(jié)構(gòu)對(duì)外層柱晶有不同程度的影響。先低溫后高溫結(jié)晶,內(nèi)層柱晶的晶體結(jié)構(gòu)對(duì)外層柱晶的影響更大;先高溫后低溫結(jié)晶,結(jié)晶溫度對(duì)外層柱晶的影響更大。
[Abstract]:Polyvinylidene fluoride (PVDF), as a semi-crystalline polycrystalline functional polymer, contains at least four different crystal structures, namely 偽, 尾, 緯, 未 crystalline phase, in which both 尾 and 緯 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 緯 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 緯 -crystal. In this paper, the blade shear method and fiber shearing method are mainly used. High content 尾 -crystalline and 緯 -crystalline PVDF thin films were prepared. The changes of 尾 -crystal and 緯 -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 偽 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. 偽 -columnar crystals can be obtained at lower temperature and annealed at high temperature. 鈫扨hase transition of 緯', growth of 偽 columnar crystal and 偽 with the increase of crystallization time at higher temperature. 鈫扵he phase transition of 緯'is carried out at the same time. Compared with the phase transition of 偽 -spherulite, the phase transition of 偽 -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.
【學(xué)位授予單位】：江蘇科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TB324

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本文編號(hào)：1621047