【作者】 朱朦琪；

【导师】 肖潭； 吴萍；

【作者基本信息】 汕头大学 ， 材料物理与化学， 2010， 硕士

【摘要】 碳纳米管(CNT)具有独特的结构和优异的理化性能,是制备聚合物基复合材料最理想的增强体之一,然而其极易团聚、与聚合物基体间界面结合力差的缺点,极大地限制了其在复合材料中的应用。为改善碳纳米管的分散性能,提高碳纳米管与基体间的界面结合力,最终制备出性能优异的复合材料,我们以多壁碳纳米管为研究对象,首先研究了不同温度下混酸氧化和4,4’-二氨基-3,3’-二氯二苯基甲烷(MOCA)改性对碳纳米管结构和性能的影响;在羧化碳纳米管的基础上进一步酯化生成溴引发剂,引发甲基丙烯酸缩水甘油酯(GMA)的原子转移自由基聚合(ATRP)反应,制备了聚甲基丙烯酸缩水甘油酯(PGMA)包裹的碳纳米管;再以混杂功能化的方法作为指导,分别制备了聚苯乙炔(PPA)包覆的不同温度下羧化碳纳米管;最后研究了PU复合材料的力学和热学性能与碳纳米管种类、配比的关系。主要结果如下:(1) 50℃和回流温度下混酸氧化碳纳米管1.5h,均可在其表面接枝上羧基和羟基等活性基团,且温度越高接枝基团数量越多,纯化效果也越好。拉曼光谱对原始多壁碳纳米管(MWNT)、50℃羧化碳纳米管(MWNT-COOH(Ⅰ))和回流温度羧化碳纳米管(MWNT-COOH(Ⅱ))的分析表明,氧化处理会在碳纳米管表面引入缺陷,导致结构有序度下降。利用DCC脱水缩合的作用原理,一步法制备MOCA接枝碳纳米管。(2)通过ATRP反应,成功地将GMA单体原位接枝到碳纳米管表面,得到PGMA包裹的碳纳米管,通过透射电子显微镜(TEM)可以明显观察到碳纳米管表面包裹的PGMA层。(3)将羧化碳纳米管和PPA加入四氢呋喃溶剂中,经超声分散5h,得到PPA包覆的混杂功能化碳纳米管,其分散性能要优于未包覆前羧化碳纳米管。(4) PU复合材料的热学性能与加入的碳纳米管种类有很大关系,当加入的是MWNT或MWNT/PPA时,复合材料的热学性能有所下降;当加入的是羧化碳纳米管、MOCA接枝碳纳米管及PPA包裹羧化碳纳米管时,复合材料的初始分解温度会有所上升,复合材料的热稳定性有一定提高。(5)碳纳米管的种类和用量对PU复合材料的拉伸强度有较大影响。当以MWNT和MWNT/PPA做为增强体时,复合材料力学性能下降;当以MWNT-COOH(Ⅰ)和MWNT-COOH(Ⅰ)/PPA做为增强体时,复合材料的拉伸强度有所提高;随着碳纳米管含量的增加,拉伸强度先升后降,在0.2%时达到最佳;当以MWNT-COOH(Ⅱ)、MOCA接枝碳纳米管和MWNT-COOH(Ⅱ)/PPA做为增强体时,复合材料的拉伸强度进一步提高,均在碳纳米管含量为0.3%时达到最佳,其中MWNT-COOH(Ⅱ)/PPA/PU复合材料拉伸强度提高最大。更多还原

【Abstract】 Carbon nanotubes (CNT) are one of the best promising reinforcement materials for polymer composites due to their unique structure and extraordinary physicochemical properties. However, their applications to polymer composites are limited because of the easy formation of aggregates and rather weak interfacial interactions between CNT and polymer matrix. In order to improve the dispersion and the interfacial behavior of CNT in polymer matrix and synthesize high-performance polymer composites, we firstly studied the effect of experimental temperature and modification of Methylene-bis-ortho-chloroanilline (MOCA) on the structure and properties of CNT; Through the esterification reaction on the basis of oxidization of multi-walled carbon nanotubes (MWNT-COOH), the MWNT-based macroinitiators, MWNT-Br was produced, and then the atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) was initiated to produce the MWNT wrapped by poly-(glycidyl methacrylate) (MWNT-g-PGMA); Under the guidance of hybrid functionalization, We synthesized different temperature oxidization of MWNT coated by PPA. Finally, the dependence of mechanical and thermal properties of PU composites on the content of different MWNT was investigated. The main results are:(1) The active groups(-COOH, -OH) could be grafted to the MWNT via oxidation with a mixture of concentrated sulfuric acid and nitric acid at different temperature. In addition, the drafted amount of active groups and dispersion effect could be enhanced with higher temperature. Raman spectra analysis of pristine MWNT, 50℃oxidization of MWNT (MWNT-COOH(Ⅰ)), refluxing-temperature oxidization of MWNT (MWNT-COOH(Ⅱ)) indicated that the oxidation treatment generated defects and reduced the structural order degree of MWNT. The MOCA had been drafted to the oxidized MWNT in one-step with the aid of condensation agent N,N’-dicyclohexylcarbodiimide (DCC).(2) The morphological structures of MWNT-g-PGMA were examined by Transmission Electron Microscope (TEM). It was clearly observed that the PGMA was grafted to the MWNT via the ATRP through the TEM images.(3) We got the hybrid functioanlization MWNT coated by PPA through the ultrasonic dispersion treatment for 5 hours, it has a better dispersion than the MWNT-COOH.(4) The thermal properties of polyurethane (PU) composites have relation to the category of functionalized MWNT (f-MWNT). When MWNT or MWNT/PPA was added to the matrix, the thermal properties of PU composites declined. When MWNT-COOH, MOCA-grafted MWNT or MWNT-COOH/PPA was added to the matrix, the temperature of initial decomposition increased and the thermal properties of PU composites were improved.(5) The category and content of f-MWNT have great influence on the tensile strength of PU composites. When the reinforcement was MWNT or MWNT/PPA, the mechanical properties of PU composites declined; When the reinforcement was MWNT-COOH(Ⅰ) or MWNT-COOH(Ⅰ)/PPA, the tensile strength of PU composites increased. The curve of tensile strength and the content of f-MWNT fell after raising, and the optimum content was 0.2wt%; When the reinforcement was MWNT-COOH(Ⅱ), MOCA-grafted MWNT or MWNT-COOH(Ⅱ)/PPA, the tensile strength of PU composites increased more, and the optimum content was 0.3wt%. Comparing the tensile strength of all kinds of PU composites, MWNT-COOH(Ⅱ)/PPA/PU had the maximum tensile strength.更多还原