聚乙烯基微—纳米复合材料介电性能研究

发布时间：2018-06-16 05:43

本文选题：微-纳米复合材料 + 聚乙烯　；参考：《哈尔滨理工大学》2017年硕士论文

【摘要】：向聚合物中添加无机纳米颗粒,可以改善其结晶行为和一系列介电性能。但由于纳米粒子粒径尺寸小,表面能大,在与聚合物共混过程中易发生团聚现象。而无机微米粒子具有优良的导热性能和耐电腐蚀性能,也可以作为填料加入到聚合物中对其进行改性。当微米粒子与纳米粒子按一定的比例配合加入到聚合物基体中,由于其微纳米之间的协同效应,有可能使得到的微纳米复合材料的电气性能有更大程度的提高。本文以低密度聚乙烯为基体,超声波剥离处理的蒙脱土粒子作为纳米填料,二氧化硅颗粒作为微米填料,采用熔融共混法分别制备了纯聚乙烯试样、纳米复合材料、微米复合材料和微-纳米复合材料。首先通过DSC试验和PLM试验对材料的微观结构进行了表征,应用红外光谱(FTIR)对材料进行了化学表征。然后对比研究了四种材料的介电强度、极化行为与介质损耗以及电导行为。最后对四种试样在不同电压等级和不同温度下进行了电树枝试验来研究材料的耐电树枝老化特性。试验结果表明,向聚乙烯中添加无机粒子改性可以改善聚乙烯的结晶,使结晶度提高并使晶胞尺寸减小且排列更加有序。无机粒子的加入并不会改变聚乙烯分子本身的结构,而是在两种无机粒子之间和无机粒子与基体之间形成了新的化学作用力。微米粒子加入会明显提高材料的击穿强度,而纳米粒子会使材料的击穿场强的分散性减小,其中微-纳米复合材料的击穿性能最优良。介质内部的极化行为会因无机粒子的加入而变得复杂,所以会有更多的界面损耗,而微-纳米复合材料由于粒子之间的协同效应会使损耗维持在一个相对偏低的水平。复合材料的电导率与纯聚乙烯试样相比有所降低,并且使温度对试样电导率的影响程度变小,无机粒子的加入会改善聚乙烯基体的介电性能。相同条件下,微-纳米复合材料中的电树枝生长长度最短且树枝形态更加稠密,说明其耐电树枝特性十分优良。并且高温情况下的电树枝由丛状向树枝状转变的临界温度点明显是微-纳米复合材料要高。说明电缆运行温度较高时,微-纳米复合材料更不容易由于电树枝的发展而导致击穿。
[Abstract]:Adding inorganic nanoparticles to the polymer can improve its crystallization behavior and a series of dielectric properties. However, the particle size is small and the surface energy is large, so it is easy to agglomerate in the process of blending with polymer. Inorganic micron particles have excellent thermal conductivity and corrosion resistance, and can be added to the polymer as fillers to modify them. When micron particles and nanoparticles are added to polymer matrix in a certain proportion, it is possible to improve the electrical properties of the composite due to the synergistic effect between microparticles and nano-particles. In this paper, pure polyethylene (PE) samples were prepared by melt blending method, in which montmorillonite particles were used as nanomaterials and silica particles were used as micron fillers. Micron composites and micro-nanocomposites. Firstly, the microstructure of the material was characterized by DSC and PLM tests, and the chemical characterization was carried out by FTIR. Then, the dielectric strength, polarization behavior, dielectric loss and conductance behavior of four kinds of materials were studied. Finally, four kinds of samples were tested at different voltage levels and different temperatures to study the aging characteristics of the materials. The experimental results show that adding inorganic particles to polyethylene can improve the crystallization of polyethylene, increase the crystallinity, decrease the size of the unit cell and make the arrangement more orderly. The addition of inorganic particles does not change the structure of polyethylene molecules, but forms a new chemical force between two inorganic particles and between inorganic particles and matrix. The addition of micron particles can obviously improve the breakdown strength of the materials, while the dispersion of the breakdown field strength of the materials will be reduced by nano-particles, among which the breakdown properties of micro-nanocomposites are the best. The polarization behavior in the medium will be complicated by the addition of inorganic particles, so there will be more interfacial losses, while the loss of micro-nanocomposites will be maintained at a relatively low level due to the synergistic effect between the particles. The electrical conductivity of the composite is lower than that of the pure polyethylene, and the influence of temperature on the conductivity of the composite is smaller. The addition of inorganic particles will improve the dielectric properties of the polyethylene matrix. Under the same conditions, the electric tree growth length is the shortest and the tree morphology is denser in the micronanocomposites, which indicates that the electric tree resistance of the composite is very good. At high temperature, the critical temperature point for the transition of electric branches from cluster to dendriform is obviously higher than that of micro-nanocomposites. The results show that micronanocomposites are less likely to break down due to the development of electric branches when the operating temperature of cables is high.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332

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