發(fā)布時間：2018-01-21 06:45

  本文關(guān)鍵詞： 碳纖維 循環(huán)伏安法 交流阻抗譜 電化學(xué)聚合 復(fù)合材料　出處：《沈陽工業(yè)大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：碳纖維增強環(huán)氧樹脂復(fù)合材料具有優(yōu)越的物理和化學(xué)性能,但是碳纖維表面活性低,與樹脂的相容性差,所以碳纖維增強環(huán)氧樹脂復(fù)合材料的性能依賴于碳纖維和樹脂基體之間的界面相容性。針對這一問題,以H2SO4為電解質(zhì),丙烯酸和丙烯酰胺為單體,利用循環(huán)伏安法對碳纖維表面進行電化學(xué)聚合改性。循環(huán)次數(shù)、單體質(zhì)量比、掃描速率、電解質(zhì)類型和H2SO4的濃度對碳纖維表面的電化學(xué)聚合和改性碳纖維的電化學(xué)阻抗譜有明顯的影響。隨著循環(huán)次數(shù)增加,碳纖維表面聚合物也增多,聚合物薄膜的電化學(xué)性能更穩(wěn)定。丙烯酸與丙烯酰胺的質(zhì)量比為3:1時,碳纖維改性效果最佳。當(dāng)掃描速度為0.05V/s,H+濃度為0.2mol/L時對電化學(xué)聚合有利。相比于H2SO4和NaOH,LiClO4為電解質(zhì)時更有利于電化學(xué)聚合。而且聚合物薄膜的氧化還原反應(yīng)是不可逆的,通過分析Nyquist圖,幅頻特性圖和相位角圖發(fā)現(xiàn)在整個頻率范圍內(nèi)的交流阻抗譜圖是半徑很大的容抗弧,聚合物薄膜接枝的碳纖維呈現(xiàn)電容性行為。FTIR、EDS和TGA分別表征碳纖維表面共聚物的化學(xué)成分和熱穩(wěn)定性。當(dāng)丙烯酸質(zhì)量與丙烯酰胺質(zhì)量比為1:1時,聚合過程中更可能產(chǎn)生丙烯酸和丙烯酰胺的交替共聚物,共聚物鏈段的長度更長,有序性會更好。電化學(xué)聚合的反應(yīng)機理:即通過單體上碳碳雙鍵的還原將丙烯酸和丙烯酰胺接枝到碳纖維表面。說明電化學(xué)聚合反應(yīng)是通過陰離子自由基加成機理進行的。在電化學(xué)還原過程中,單體接枝到了碳纖維表面形成的陰離子自由基上。通過測試超純水和碳纖維的接觸角,發(fā)現(xiàn)與未改性碳纖維相比,改性碳纖維和超純水的接觸角明顯減小,并且總是小于90°。碳纖維表面活性增加,潤濕性明顯提高。對改性前后碳纖維/環(huán)氧樹脂復(fù)合材料力學(xué)性能進行了研究。與未改性碳纖維/環(huán)氧樹脂復(fù)合材料的拉伸強度比較,改性后碳纖維/環(huán)氧樹脂復(fù)合材料的拉伸強度有了很大的提高,特別是碳纖維質(zhì)量分數(shù)為0.45%時,拉伸強度提高了73%。聚合物接枝的碳纖維復(fù)合材料的屈服強度提高約68.3%。經(jīng)電化學(xué)改性后,未處理的碳纖維復(fù)合材料的斷裂伸長率比共聚物接枝的碳纖維增強環(huán)氧樹脂復(fù)合材料高出近1.88倍。利用掃描電鏡觀察電化學(xué)聚合改性后碳纖維表面形貌。隨著掃描速率的增加,聚合物薄膜沿碳纖維軸向生長,有許多較深的溝槽。碳纖維粗糙的部分會形成更多的聚合活性點。碳纖維復(fù)合材料斷口掃描電鏡照片表明,未改性碳纖維表面光滑,沒有環(huán)氧樹脂殘余,碳纖維與環(huán)氧樹脂之間有明顯空隙,而改性碳纖維表面粗糙,有環(huán)氧樹脂粘附在碳纖維表面,說明改性后碳纖維與環(huán)氧樹脂界面性能很好。
[Abstract]:Carbon fiber reinforced epoxy composites have excellent physical and chemical properties, but carbon fiber has low surface activity and poor compatibility with resin. Therefore, the properties of carbon fiber reinforced epoxy composites depend on the interfacial compatibility between carbon fiber and resin matrix. To solve this problem, H _ 2SO _ 4 as electrolyte, acrylic acid and acrylamide as monomer. The surface of carbon fiber was modified by electrochemical polymerization by cyclic voltammetry. The type of electrolyte and the concentration of H _ 2SO _ 4 have obvious influence on the electrochemical polymerization of carbon fiber surface and electrochemical impedance spectroscopy of modified carbon fiber. With the increase of cycle times, the surface polymer of carbon fiber also increases. When the mass ratio of acrylic acid to acrylamide is 3: 1, carbon fiber modification is the best, and the scanning speed is 0.05 V / s. When H concentration is 0.2 mol / L, it is advantageous to electrochemical polymerization, compared with H _ 2SO _ 4 and NaOH. The redox reaction of the polymer film is irreversible, and the Nyquist diagram is analyzed. The amplitude-frequency characteristic diagram and phase angle diagram show that the impedance spectrum of AC in the whole frequency range is capacitive arc with a large radius, and the carbon fiber grafted by polymer film shows capacitive behavior. The chemical composition and thermal stability of carbon fiber surface copolymers were characterized by EDS and TGA when the mass ratio of acrylic acid to acrylamide was 1: 1. It is more likely to produce alternative copolymers of acrylic acid and acrylamide during the polymerization process, and the length of the chain segments of the copolymers is longer. The reaction mechanism of electrochemical polymerization is as follows:. That is to say, acrylic acid and acrylamide were grafted onto carbon fiber surface by the reduction of carbon-carbon double bond on monomer. The electrochemical polymerization was carried out by the mechanism of anionic radical addition. The monomer was grafted onto the anionic free radical formed on the surface of carbon fiber. The contact angle of ultrapure water and carbon fiber was obviously reduced compared with that of unmodified carbon fiber. And it is always less than 90 擄. The surface activity of carbon fiber increases. The mechanical properties of carbon fiber / epoxy resin composite before and after modification were studied. The tensile strength of carbon fiber / epoxy resin composite was compared with that of unmodified carbon fiber / epoxy resin composite. The tensile strength of the modified carbon fiber / epoxy composites has been greatly improved, especially when the carbon fiber mass fraction is 0.45. The tensile strength was increased by 73 and the yield strength of the polymer grafted carbon fiber composites was increased by about 68.3%. The elongation at break of untreated carbon fiber composites is about 1.88 times higher than that of copolymers grafted carbon fiber reinforced epoxy composites. The surface morphology of carbon fiber modified by electrochemical polymerization is observed by scanning electron microscope. As the scanning rate increases. The polymer film grows along the axial direction of carbon fiber, and there are many deep grooves. The coarse part of carbon fiber will form more polymeric active points. The SEM photos of the fracture surface of carbon fiber composite show that the polymer film has many deep grooves. The surface of unmodified carbon fiber is smooth, there is no epoxy resin residue, there is an obvious gap between carbon fiber and epoxy resin, while the surface of modified carbon fiber is rough, and epoxy resin adheres to the surface of carbon fiber. The results show that the interfacial properties of modified carbon fiber and epoxy resin are very good.
【學(xué)位授予單位】：沈陽工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ342.742;TB332

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