电化学聚合改性碳纤维及其复合材料性能的影响

发布时间：2018-01-21 06:45

本文关键词： 碳纤维循环伏安法交流阻抗谱电化学聚合复合材料　出处：《沈阳工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：碳纤维增强环氧树脂复合材料具有优越的物理和化学性能,但是碳纤维表面活性低,与树脂的相容性差,所以碳纤维增强环氧树脂复合材料的性能依赖于碳纤维和树脂基体之间的界面相容性。针对这一问题,以H2SO4为电解质,丙烯酸和丙烯酰胺为单体,利用循环伏安法对碳纤维表面进行电化学聚合改性。循环次数、单体质量比、扫描速率、电解质类型和H2SO4的浓度对碳纤维表面的电化学聚合和改性碳纤维的电化学阻抗谱有明显的影响。随着循环次数增加,碳纤维表面聚合物也增多,聚合物薄膜的电化学性能更稳定。丙烯酸与丙烯酰胺的质量比为3:1时,碳纤维改性效果最佳。当扫描速度为0.05V/s,H+浓度为0.2mol/L时对电化学聚合有利。相比于H2SO4和NaOH,LiClO4为电解质时更有利于电化学聚合。而且聚合物薄膜的氧化还原反应是不可逆的,通过分析Nyquist图,幅频特性图和相位角图发现在整个频率范围内的交流阻抗谱图是半径很大的容抗弧,聚合物薄膜接枝的碳纤维呈现电容性行为。FTIR、EDS和TGA分别表征碳纤维表面共聚物的化学成分和热稳定性。当丙烯酸质量与丙烯酰胺质量比为1:1时,聚合过程中更可能产生丙烯酸和丙烯酰胺的交替共聚物,共聚物链段的长度更长,有序性会更好。电化学聚合的反应机理:即通过单体上碳碳双键的还原将丙烯酸和丙烯酰胺接枝到碳纤维表面。说明电化学聚合反应是通过阴离子自由基加成机理进行的。在电化学还原过程中,单体接枝到了碳纤维表面形成的阴离子自由基上。通过测试超纯水和碳纤维的接触角,发现与未改性碳纤维相比,改性碳纤维和超纯水的接触角明显减小,并且总是小于90°。碳纤维表面活性增加,润湿性明显提高。对改性前后碳纤维/环氧树脂复合材料力学性能进行了研究。与未改性碳纤维/环氧树脂复合材料的拉伸强度比较,改性后碳纤维/环氧树脂复合材料的拉伸强度有了很大的提高,特别是碳纤维质量分数为0.45%时,拉伸强度提高了73%。聚合物接枝的碳纤维复合材料的屈服强度提高约68.3%。经电化学改性后,未处理的碳纤维复合材料的断裂伸长率比共聚物接枝的碳纤维增强环氧树脂复合材料高出近1.88倍。利用扫描电镜观察电化学聚合改性后碳纤维表面形貌。随着扫描速率的增加,聚合物薄膜沿碳纤维轴向生长,有许多较深的沟槽。碳纤维粗糙的部分会形成更多的聚合活性点。碳纤维复合材料断口扫描电镜照片表明,未改性碳纤维表面光滑,没有环氧树脂残余,碳纤维与环氧树脂之间有明显空隙,而改性碳纤维表面粗糙,有环氧树脂粘附在碳纤维表面,说明改性后碳纤维与环氧树脂界面性能很好。
[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 掳. 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.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ342.742;TB332

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