碳纳米管诱导聚乳酸共混复合材料结构及性能变化的研究

发布时间：2018-03-01 08:50

本文关键词： 聚乳酸共混物碳纳米管选择性分布形态结构电学性能形状记忆行为　出处：《西南交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：近些年来,纳米复合材料以其优异的综合性能受到了研究者的广泛关注。其中,碳纳米管(Carbon nanotubes, CNTs)因其较大的长径比、极高的强度和模量、优异的导电和导热性能而被广泛地应用于聚合物改性技术中,成为纳米复合材料领域研究的热点。对于只含有单一聚合物的CNTs纳米复合材料而言,虽然CNTs的引入能在一定程度上改善聚合物的综合性能,但改善效果有限,而且所需CNTs的含量较大,成本较高,无法满足人们的日益增长的使用需求。因此,开发新型的基于聚合物共混物的CNTs填充改性纳米复合材料势在必行。对于含CNTs的聚合物共混纳米复合材料而言,其性能除了依赖于共混物各个组分的本身性质之外,还在很大程度上受到共混物形态结构及CNTs选择性分布的影响。本论文通过向聚乳酸(Poly(L-lactic acid), PLLA)基共混物中引入CNTs,采用简单的熔融共混制备得到功能性共混纳米复合材料。旨在通过CNTs的引入,研究CNTs在不相容共混物中的选择性分布对电性能的影响；并且通过对熔融加工条件的调控,研究CNTs对共混复合材料形态演化的作用机制；另外,通过调控共混复合材料形态结构及CNTs选择性分布,研究CNTs的网络结构对共混纳米复合材料的形状记忆行为的影响。得到主要结果如下：(1)通过熔融共混的方法成功制备PLLA接枝马来酸酐(PLLA grafted maleic anhydride, PLLA-g-MA)。在PLLA-g-MA分子极性和粘度的共同作用下,CNTs分布在PLLA-g-MA和高密度聚乙烯(Polyethyene, HDPE)两相界面上；样品得到较低的导电逾渗阂值(0.49 wt%)。同时观察样品形貌发现,CNTs的引入加速了共混复合材料形态发展进程。(2)分别选取三个不同的共混时间点及剪切强度作为共混条件变量,制备得到PLLA-g-MA/HDPE共混物及PLLA-g-MA/HDPE/CNTs共混复合材料。形貌观察及流变分析表明,无论在不同共混时间下还是不同剪切强度下,CNTs均加速了共混复合材料的形态发展进程。这是由于CNTs的存在一方面使体系粘度增加,局部剪切应力增大,加速分散相粒子变形、破裂的过程；另一方面,CNTs在界面上的选择性分布阻碍了分散相粒子的融合,使分散相具有较小的尺寸。导电性能测试表明,当共混时间为6 min,转速为60 rpm时,所制备的共混复合材料的导电性能最好。(3)以热塑性聚氨酯(Thermoplastic polyurethane, TPU)为母料,通过两步法熔融共混制备得到PLLA/TPU/CNTs共混复合材料。微观结构表征发现,CNTs分布在TPU中,且由于CNTs的填充作用,TPU相尺寸随CNTs含量增加而逐渐变大。不同温度下的热致形状回复行为表明,CNTs阻碍共混复合材料的热致回复行为,且CNTs含量越高,这种阻碍作用越明显。分析认为,这是由于CNTs的网络结构抑制了TPU分子链运动,阻碍其形状回复过程。相反地,随着CNTs含量的增多,共混复合材料的电致回复行为变得更明显。无论热致回复记忆行为还是电致形状记忆行为,温度的升高都有利于材料的形状回复过程。
[Abstract]:In recent years, nano composite materials for their excellent properties has attracted much attention of researchers. Among them, carbon nanotubes (Carbon, nanotubes, CNTs) because of its high aspect ratio, high strength and modulus, excellent electrical conductivity and thermal conductivity have been widely used in polymer modification technology, has become a hot spot the research field of nano composite materials. The CNTs nano composite material contains only a single polymer, although the introduction of CNTs can improve the comprehensive performance of the polymer to a certain extent, but the improvement is limited, but also required the content of CNTs is large, high cost, unable to meet the growing needs. Therefore, the development of new the polymer blends based on CNTs filled imperative nano composite material. For polymer nanocomposites containing CNTs, but its performance depends on the blend In addition to a component of nature, are greatly affected by the blend morphology and CNTs selective distribution. This paper through to polylactic acid (Poly (L-lactic acid), PLLA) introduced CNTs based blends by melt blending process, simple preparation of functional blend nanocomposites. Designed by CNTs the introduction of CNTs in incompatible blends in the distribution of selective effects on the electrical performance; and through the regulation of melt processing conditions, effects of CNTs on the mechanism of the evolution of composite morphology; in addition, by regulating the blend morphology and CNTs selective distribution, influence of shape memory behavior of the network structure of CNTs the blending nano composite material. The main results are as follows: (1) preparation of PLLA grafted with maleic anhydride by melt blending method for grafted maleic (PLLA anhydride, P LLA-g-MA). Interaction between PLLA-g-MA molecular polarity and viscosity, the distribution of CNTs in PLLA-g-MA and high density polyethylene (Polyethyene, HDPE) interface; samples get lower conductive threshold (0.49 wt%). At the same time to observe the morphology of the samples showed that the introduction of CNTs accelerated the development of morphology of blends and composites (2) three. The process of blending different time and shear strength were selected as blending condition variables, the prepared PLLA-g-MA/HDPE blends and PLLA-g-MA/HDPE/CNTs composites. Morphology and rheological analysis showed that no matter in different time or different blends under shear strength, CNTs accelerate the development process of the morphology of blends and composites this is due to the presence of CNTs. On the one hand, the viscosity of the system increased, the local shear stress increases, accelerated particles deformation and rupture process; on the other hand, the CNTs in the interface The fusion of the selective distribution of hindered particles, the dispersed phase has a smaller size. The conductive performance tests show that when the mixing time is 6 min, the speed is 60 rpm, the conductive properties of prepared composites prepared by the best. (3) with thermoplastic polyurethane (Thermoplastic polyurethane, TPU) for the two step of melt blending masterbatch was prepared by blending PLLA/TPU/CNTs composite material. The characterization of the microstructure, the distribution of CNTs in TPU, and because the filling effect of CNTs, the size of TPU phase increased with the increase of CNTs content. The different temperature of thermally induced shape recovery behavior showed that the recovery behavior of CNTs blend composite caused by obstacles the heat, the higher the content of CNTs, the blocking effect is more obvious. The analysis thinks, this is because the network structure of CNTs inhibited TPU molecular chain movement, hinder the shape recovery process. On the contrary, with the increase of CNTs content, The electrical recovery behavior of the composites is more obvious. No matter the thermal recovery memory behavior or the electrical shape memory behavior, the increase of temperature is beneficial to the shape recovery process of the composites.

【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332;O613.71

【引证文献】