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  本文選題：干噴濕紡　切入點(diǎn)：PAN初生纖維　出處：《山東大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：聚丙烯腈(PAN)原絲質(zhì)量是提高碳纖維性能的關(guān)鍵因素,針對干噴濕紡工藝中的各階段纖維結(jié)構(gòu)與性能展開系統(tǒng)性研究,全面了解PAN初生纖維結(jié)構(gòu)成形以及后續(xù)紡絲各階段的纖維結(jié)構(gòu)轉(zhuǎn)變過程,對改善PAN原絲質(zhì)量和提高碳纖維拉伸強(qiáng)度具有實(shí)際指導(dǎo)優(yōu)化的作用。本文中我們采用了 X射線衍射儀(XRD)、高分辨透射電鏡(HRTEM)、掃描電鏡(SEM)、差示掃描量熱法(DSC)、熱重分析(TG)等測試分析技術(shù),對不同紡絲原液參數(shù)和凝固浴條件的初生纖維結(jié)構(gòu)與性能,以及制備過程當(dāng)中PAN纖維的結(jié)構(gòu)轉(zhuǎn)變規(guī)律展開了系統(tǒng)性研究工作。干噴濕紡初生纖維階段是PAN原絲結(jié)構(gòu)形成的最初以及最關(guān)鍵的制備過程。初生纖維結(jié)構(gòu)對原絲質(zhì)量有重要的影響。研究了凝固浴不同溫度、牽伸比以及不同黏均分子量、固含量對PAN初生纖維結(jié)構(gòu)和性能的影響。凝固浴溫度能夠影響初生絲條的雙擴(kuò)散過程,能夠影響初生纖維截面形狀;隨著牽伸倍數(shù)的提高,初生纖維結(jié)晶度、晶粒尺寸和沸水縮率逐漸增長,分子鏈緊密排列,微孔尺寸和數(shù)量降低,初生纖維的纖度降低、拉伸強(qiáng)度增大、斷裂伸長率升高,同時其相應(yīng)的離散系數(shù)也變小;隨著黏均分子量和原液固含量的增加,紡絲原液中PAN分子鏈的纏結(jié)點(diǎn)密度增加,原液黏度升高,初生纖維纖度減小,拉伸強(qiáng)度升高。固含量較高的紡絲原液對干噴濕紡工藝制備優(yōu)質(zhì)初生纖維有利。研究了干噴濕紡過程中各階段PAN纖維微觀結(jié)構(gòu),以及結(jié)晶結(jié)構(gòu)對PAN原絲的力學(xué)性能和熱性能的影響。干噴濕紡制備的PAN纖維表面光滑、雜質(zhì)少、表面缺陷較少。在原絲制備過程中,PAN纖維的晶粒尺寸升高、結(jié)晶度呈上升趨勢,結(jié)晶結(jié)構(gòu)隨之完善,其中,牽伸能夠提高結(jié)晶度,致密化和熱定型能夠增進(jìn)晶粒生長;隨著紡絲的進(jìn)行,PAN纖維纖度減小,致密性提高,拉伸強(qiáng)度升高,斷裂伸長率降低。原絲的晶體結(jié)構(gòu)對其力學(xué)性能和熱性能有重要的影響,結(jié)晶結(jié)構(gòu)越完善,對原絲的力學(xué)性能越有益,預(yù)氧化過程中的環(huán)化反應(yīng)越難發(fā)生,反應(yīng)的起始溫度趨于高溫,而且能夠預(yù)防PAN分子鏈熱分解。利用HRTEM表征PAN纖維微觀結(jié)構(gòu),利用環(huán)氧樹脂對紡絲各階段PAN纖維進(jìn)行包埋,采用超薄切片技術(shù),得到與纖維軸向相垂直的橫向切片和相平行的縱向切片,切片厚度為50-70nm,有利于電子束穿透纖維切片。其中,環(huán)氧樹脂只起固定纖維的作用,對圖像襯度沒有增強(qiáng)效果。初生纖維內(nèi)部組織是片層結(jié)構(gòu),片層垂直于纖維軸向排列,片層之間的孔隙較多;在凝固浴預(yù)牽伸階段,開始出現(xiàn)微原纖結(jié)構(gòu),微原纖平行于纖維軸向排列,在多級牽伸和致密化后,微原纖排列更為緊密,微原纖之間并不是平行排列,微原纖之間會有交錯、纏繞,微原纖的直徑約30-50nm。微原纖之間存在孔隙,孔隙在拉力的作用下,截面為狹長型,在紡絲過程中,孔隙數(shù)量減少,但不能完全消除。
[Abstract]:The quality of polyacrylonitrile (pan) precursor is the key factor to improve the properties of carbon fiber. A comprehensive understanding of the formation of the primary fiber structure of PAN and the process of fiber structure transformation at various stages of subsequent spinning, In this paper, we adopt X-ray diffractometer, high resolution transmission electron microscope, scanning electron microscope, scanning electron microscope, differential scanning calorimetry, thermal gravimetric analysis. Test and analysis techniques such as TG, The structure and properties of primary fibers with different spinning solution parameters and coagulation bath conditions were studied. The structure transformation of PAN fiber was studied systematically. The initial and most critical preparation process of PAN precursor was the stage of dry spray wet spinning primary fiber. The primary fiber structure of PAN fiber was the most important one. Quality has an important effect. The different temperature of solidification bath is studied. The effects of drawing ratio, average molecular weight of different viscosity, solid content on the structure and properties of PAN primary fiber, the effect of solidification bath temperature on the double diffusion process of primary filament strip and the shape of primary fiber section, and the effect of the drawing ratio on the structure and properties of the primary fiber, The crystallinity, grain size and boiling water shrinkage of the primary fibers increased gradually, the molecular chains were arranged tightly, the size and number of micropores decreased, the size of the primary fibers decreased, the tensile strength increased, and the elongation at break increased. With the increase of viscosity average molecular weight and solid content of raw solution, the entanglement point density of PAN molecular chain in spinning solution increased, the viscosity of original solution increased, and the size of primary fiber decreased. The higher tensile strength and the higher solid content of the spinning solution are beneficial to the preparation of high quality primary fibers by dry spray wet spinning. The microstructure of PAN fibers in different stages of dry jet wet spinning is studied. And the effect of crystal structure on the mechanical and thermal properties of PAN precursor. The PAN fiber prepared by dry spray wet spinning has a smooth surface, less impurity and less surface defects. The grain size of pan fiber increases and the crystallinity increases during the preparation process. The crystalline structure was improved, among which, the crystallinity was increased by drawing, and the grain growth was improved by densification and heat setting, and the fineness, densification and tensile strength of pan fiber decreased with spinning. The crystal structure of the precursor has an important effect on its mechanical and thermal properties. The more perfect the crystal structure, the more beneficial to the mechanical properties of the precursor, and the more difficult the cyclization occurs during the preoxidation process, The initial temperature of the reaction tends to be high, and it can prevent the thermal decomposition of PAN molecular chain. The microstructure of PAN fiber is characterized by HRTEM, and the PAN fiber in all stages of spinning is encapsulated by epoxy resin. The horizontal and vertical sections perpendicular to the axial phase of the fibers were obtained. The thickness of the slices was 50-70 nm, which was favorable for the electron beam to penetrate the fibers. There is no enhancement effect on image contrast. The inner structure of primary fiber is lamellar structure, the lamellae is perpendicular to the axial arrangement of the fiber, and there are more pores between the lamellae, and the microfibrillar structure begins to appear in the predraft stage of solidification bath. The microfibrils are arranged in parallel to the axial direction of the fibers. After multistage drafting and densification, the arrangement of the microfibrils is more compact, and there is no parallel arrangement between the microfibrils, and there will be interlacing and winding between the microfibrils. The diameter of the microfibrils is about 30-50 nm. There are pores between the microfibrils. The cross-section of the microfibrils is narrow and narrow under the action of tensile force. During spinning, the number of pores decreases, but it can not be completely eliminated.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ342.31

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