【作者】 陈小金；

【导师】 陈宪宏；

【作者基本信息】 湖南大学 ， 材料学， 2006， 硕士

【摘要】 碳纳米管(CNTs)以特有的力学、电学和化学特性以及独特的准一维管状分子结构,在未来高科技领域中具有许多潜在应用价值,迅速成为化学、物理学及材料科学领域的研究热点。然而,CNTs呈化学惰性且不溶于常见的溶剂,这成为开展对其研究与应用的最大障碍。鉴于此,本研究利用丁二酸酰基过氧化物对多壁碳纳米管(MWCNTs)进行侧壁羧酸功能化,以增加其化学活性和分散性;在此基础上利用原位缩聚法,实现了聚氨酯(PU)在MWCNTs侧壁上的接枝,并考察了不同功能化和不同含量的碳管对MWCNTs/PU复合材料的力学及热性能的影响。首先,采用自由基加成反应的方法,利用丁二酸酰基过氧化物对MWCNTs进行侧壁羧酸功能化,通过光谱对产物进行了表征,并考察了其分散性。结果表明:羧基自由基的进攻导致MWCNTs侧壁部分的sp~2杂化碳原子转变成sp~3杂化,实现了MWCNTs的侧壁羧基功能化,羧基数量较纯化的MWCNTs有一定程度的增加。电镜结果表明,侧壁功能化后的MWCNTs缠绕程度降低。此外,MWCNTs侧壁羧基功能化使得其悬浮液有更高的ζ电位,MWCNTs之间的静电排斥作用也随之增强,悬浮液呈现较好的分散稳定性。其次,利用原位缩聚法,在侧壁功能化后MWCNTs上进行了PU接枝改性,并对接枝效果进行了表征。结果表明:该接枝过程结合了“grafting to”和“grafting from”两种接枝方法的优点,保障了PU在碳管上的接枝效率。MWCNTs表面接枝上了一层厚度为2~5nm的PU,表面呈凹凸不平的状态。TG结果表明PU接枝率达到54%左右。最后,采用原位复合法制备了不同功能化和不同含量的MWCNTs/PU复合材料,考察其对复合材料的力学及热性能的影响。结果表明:随着MWCNTs含量的增加,复合材料的拉伸强度和断裂伸长率呈现先增加后下降的变化趋势,MWCNTs的含量为1%左右时复合材料的性能最优,侧壁功能化更有利于提高复合材料的力学性能。另外,MWCNTs的加入对复合材料中基体PU软段的T_g和硬段结晶有着非常复杂的影响。TEM结果表明,碳管含量小于1%时在基体中有较好的分散,特别是侧壁功能化的MWCNTs在局部区域出现了单分散情况。更多还原

【Abstract】 Carbon nanotubes(CNTs) has become the research focus of chemistry physics and materials science rapidly, and has a lot of potential applications in the future Hi-Tech field, due to its peculiar mechanical, electronic, chemical properties and unique one-dimensional tubal structure. However, CNTs is chemical inertia and cannot be dissoluble in general organic solvents, which become most serious impediment during developing its researches and applications. In term of these, sidewall carboxyl-functionalization was carried out between multiwalled carbon nanotubes(MWCNTs) and succinic acyl peroxide in order to improve its chemical active and solubility in the paper. On the basis of this, polyurethane(PU) was grafted from MWCNT sidewalls via in situ polycondensation, and the effect of different content and modification MWCNTs on mechanical and thermal properties of MWCNTs/PU composites was investigated.Firstly, sidewall carboxyl-functionalization was carried out between MWCNTs and succinic acyl peroxide via the approach of free radical addition reaction, the resulted product was characterized by spectroscopy and its solubility was surveyed. The results showed that attack of carboxyl free radical resulted in the conversion of some C atom from sp~2 hybrid to sp~3 hybrid on MWCNT sidewalls, which resulted that sidewall carboxyl-functionalization MWCNTs was achieved and the quantity of sidewall carboxyl group had a certain increase compared with purified MWCNTs. TEM results showed that the degree of MWCNT twining was reduced after sidewall functionalization. Moreover, sidewall carboxyl-functionalization caused MWCNT suspension have higherζelectric potential, therewith inter-tube electrostatic exclusion effect among MWCNTs was strengthened also, so its suspension had higher dispersion stability.Secondly, sidewall functionalization MWCNTs was modified by grafted with polyurethane via in situ polycondensation approach, and the modification effect was characterized. The results showed that the graft process was combined with two approaches of“grafting to”and“grafting from”, which ensure the graft efficiency of MWCNTs. MWCNTs were tethered a layer of polyurethane with a thickness in the range of 2~5 nm, and its surfaces presented a“bumpy”sidewall morphology. TG analysis showed that a graft rate of PU is up to about 54%.Finally, MWCNTs/PU composites with different modification and different content MWCNTs were prepared via in situ complex approach, and the effect of them on mechanical and thermal properties was investigated. The results showed that tensile strength and elongation at break of composites appeared the variation tendency of dropped after increasing更多还原