【作者】 江枫丹；

【导师】 张立群；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2009， 博士

【摘要】 碳纳米管是一类长径比极大的中空管状结构材料。研究表明碳纳米管具有很高的轴向强度,优异的导电、导热、耐高温等物理性能,被认为是当前最理想的聚合物填料,可用于制备高性能、多功能性能新型聚合物复合材料。近年来,碳纳米管/聚合物复合材料的研究逐渐成为新材料领域研究工作者的热点。本文采用不同方法成功制备了聚氨酯/碳纳米管纳米复合材料,考察了聚氨酯/碳纳米管纳米复合材料的结构与性能,并对其性能作了系统的研究。在论文的第一部分中,采用熔融共混法成功制备了高填充的碳纳米管/热塑性聚氨酯纳米复合材料,电镜观察结果说明,直接的熔融共混法制备的高填充的碳纳米管/热塑性聚氨酯纳米复合材料中,碳纳米管在双辊的强烈剪切力和高温作用下均匀分散在聚氨酯基体中,未处理的碳纳米管在聚氨酯基体中的分散呈纳米级分散状态。XRD和DSC分析结果表明,对于热塑性聚氨酯/碳纳米管复合体系,碳纳米管的加入只是稍微改变了聚氨酯的微相分离结构。通过力学性能、动态机械热分析、功能性能的测试,发现热塑性聚氨酯/碳纳米管纳米复合材料的力学性能与碳纳米管用量的关系与短纤维/橡胶复合材料的力学性能表现规律是相似的,碳纳米管的加入对聚氨酯在高温环境下（120℃）的力学性能是有增强作用的;碳纳米管的加入对复合材料的动态储能模量有明显的增强效果,特别是在橡胶态下,纳米复合材料的动态模量比纯聚氨酯大幅度提高,随着碳纳米管用量的增加,所得复合材料的模量逐渐提高,而且橡胶态到粘流态的转变温度升高,碳纳米管的加入改善了热塑性聚氨酯的耐热性;复合材料的导电性能提高,还具有摩擦系数降低,磨损性能提高以及一定的导热性能。当碳纳米管加入量为40 phr时,热塑性聚氨酯/碳纳米管复合材料的导电率为1.1S·m^-1,复合材料的导电逾渗值在10 vol%MWNT左右。在论文的第二部分,首先采用熔融共混法制备了热塑性聚氨酯/碳纳米管复合体系,然后通过退火热处理的方式对碳纳米管/热塑性聚氨酯复合体系进行了退火处理。主要研究了退火热处理对热塑性聚氨酯微观结构的影响以及热塑性聚氨酯/碳纳米管纳米复合材料导电性能的影响。结果表明,退火热处理过程改变了聚氨酯的微相分离结构;通过退火热处理方法降低了热塑性聚氨酯/碳纳米管纳米复合材料的导电逾渗值。复合材料熔融状态下热处理对于热塑性聚氨酯/碳纳米管复合体系,有利于碳纳米管聚集絮凝强化网络结构从而提高材料的导电性能,降低导电逾渗值。论文的第三部分中,采用十二烷基磺酸钠表面活性剂,与碳纳米管、水性聚氨酯乳液超声共混制备了聚氨酯/碳纳米管稳定悬浮液,通过喷雾干燥法成功制备了聚氨酯/碳纳米管纳米复合材料。喷雾工艺条件为:进气温度190℃,进料率为20%。电镜观察结果表明未处理的碳纳米管在聚氨酯基体中分散均匀。X-射线衍射测试表明碳纳米管的加入对聚氨酯的微相结构影响较小。导电性能测试结果表明碳纳米管的加入提高了复合材料的导电性能。随着碳纳米管体积分数的增加,聚氨酯/碳纳米管纳米复合材料的电导率逐渐增大,填充碳纳米管的聚氨酯纳米复合材料的导电逾渗值约为5%。另外,该复合材料还表现出导热性能,是一种综合性能优异的纳米复合材料。本文的最后通过静电纺丝技术制备了聚氨酯/碳纳米管复合纤维。聚氨酯/碳纳米管复合纤维的静电纺丝的适宜工艺条件:电压调至15kV,流速调至2ml/h,收集钢板到喷嘴的距离调至25cm。扫描电镜观察表明其复合纤维的直径均达到了纳米级别。透射电镜观察发现碳纳米管在复合纤维中呈一定的取向排列。XRD、DSC分析结果说明碳纳米管的加入基本没有影响聚氨酯的微观结构。随着碳纳米管用量的增加,复合材料的导电性能有一定的提高。更多还原

【Abstract】 Carbon nanotubes have excellent mechanical strength, electrical and thermal conductivity and thermal stability, which is considered to be the optical filler for polymer materials. Carbon nanotubes is a hollow tubular material possessing high aspect ratio. Recently, many researches focus on the incorporation of carbon nanotubes in polymer materials. In this paper, polyurethane/multi-walled carbon nanotubes (PU/MWNT) nanocomposites were successfully fabricated through different compounding technology, the structure and properties of PU/MWNT nanocomposites were systematically investigated.Firstly, a melt blending process has been employed to prepare nanocomposites based on thermoplastic polyurethane (TPU) and MWNT. The content of MWNT filled in TPU was increased till 40phr (parts per hundreds of rubber).The morphological, structural and mechanical properties of the resulting TPU nanocomposites were systematically investigated using scanning electron microscope (SEM), transmission electron microscope (TEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA) and tensile testing. The results indicated that the unmodified MWNT were dispersed finely and uniformly in the TPU matrix beyond expectation, and the microphase separation structures of the TPU nanocomposites were slightly affected by the presence of MWNT. The mechanical properties of the TPU nanocomposites containing various amounts of MWNT at both room temperature and 120℃were studied, which demonstrated that the modulus of TPU were greatly increased and the high temperature tensile strength of TPU was also prominently improved when MWNT content is higher. Moreover, the TPU nanocomposites exhibited improved thermal and electrical conductivities that might mean the TPU/MWNT nanocomposites have potential application as multi-functional materials.In addition flocculation method through annealing the nanocomposites at higher molding temperature has been adopted to improve the electrical conductivity of the nanocomposites. XRD experiment shows that the microphase separation structures of the TPU nanocomposites are affected by annealing heat treatment. Annealing heat treatment is in favor of increasing electrical conductivity of the nanocomposites and the percolation threshold value in electricity of the annealed TPU/MWNT nanocomposites is lower by contrast to the TPU/MWNT nanocomposites. Secondly, a spray drying approach has been adopted to prepare polyurethane (PU)/MWNT nanocomposites. Through the SEM observation, the unmodified MWNT were dispersed finely and uniformly in the PU matrix. XRD experiment indicates that the microphase separation structures of the PU nanocomposites were slightly affected by the presence of MWNT. In the electrical conductivity test, the electrical conductivity of the nanocomposites is gradually improved with increasing MWNT content as expected. The percolation threshold of the PU nanocomposites filled with MWNT is about 5vol %.In the final part, PU/MWNT composite fiber has been prepared by electrospinning, their structure and the electrical conductivity property have also been studied. SEM and TEM images show that the composite fibers have the diameter of nano scale and MWNT in the composite fibers have been aligned partly.更多还原