空间限域强制组装法制备高性能聚合物基导电复合材料机理的研究

发布时间：2018-04-22 19:22

本文选题：复合材料 + 空间限域　；参考：《北京化工大学》2017年博士论文

【摘要】：聚合物基导电复合材料是最重要的聚合物功能复合材料之一,在能量存储,电池电极,3D打印材料,电磁屏蔽,柔性显示器,智能传感器等方面有广泛的应用需求。理论与实践表明,在聚合物基体中形成连续紧密的导电填料网络是制备超高电导率聚合物基复合材料的关键。传统方法普遍通过增加导电填料的体积分数至电导率突升的逾渗阈值以上。由于聚合物基体本身电导率很低,通过在绝缘的聚合物基体中加入大长径比或大比表面积的导电填料,如炭黑粒子、碳纤维、片状石墨、碳纳米管和石墨烯,并采用合适的加工混合方法在聚合物基体中构建导电网络是当下研究聚合物基导电复合材料的焦点。目前,主要有三种构建导电网络的方法:导电填料自组装法、双连续相法和相分离法。虽然达到逾渗阈值后继续增加填料的体积分数,还可以进一步提高复合材料的电导率,但电导率的增加非常缓慢,却造成了材料加工性能和力学性能的大幅下降。电导率无法进一步大幅度提升的主要原因,在于导电填料间的平均间距对复合材料电导率的影响远大于填料体积分数的影响。为了进一步大幅度提升复合材料的导电性能,本文提出了一种旨在有效减小导电粒子平均间距的导电网络构建方法:空间限域强制组装法(SCFNA),其核心就是通过机械手段,对共混体系进行空间限域挤压和界面微纳米机械组装,从而对功能分散相施加远大于自组装作用力的“强制组装力”,强制“挤走”导电粒子间的聚合物,实现了导电网络的密实化,为大幅度提高导电性能提供了可能性。本文主要研究内容包括:1,采用该方法分别选取了热固性聚二甲基硅氧烷(PDMS)和热塑性聚丙烯(PP)两种聚合物基体,选用短切碳纤维(SCF)为导电填料,制备并获得了导电性能比传统共混法电导率高出数倍甚至数量级提高的导电复合材料PDMS/SCF和PP/SCF。导电渗流阈值仅为0.45wt%和3.5wt%。研究了加工参数、填料浓度、压缩厚度、微结构阵列对复合材料导电性能的影响。发现压缩厚度是除填料浓度外影响复合材料电导率的一个重要因素,尤其在高填料浓度下。验证了空间限域强制组装法制备高性能导电复合材料的可行性和性能提升潜力。2,采用空间限域强制组装法制备了三元导电复合材料,对比石墨烯、超导炭黑粒子,发现多壁碳纳米管与短切碳纤维协同组合复合材料导电性能最优。同时三种组份的加工混合顺序明显影响复合材料的导电性能和机械性能,改变三组份PDMS、(导电炭黑)CCB、SCF混合加工顺序,PDMS/SCF/CCB复合材料的导电性能和力学性能发生变化。采用PDMS与CCB先密炼共混后再加入SCF共混的加工顺序制备的复合材料导电性能最优,而采用SCF与CCB混匀后再加入PDMS密炼共混的加工顺序制备的复合材料力学性能最优。3,采用空间限域强制组装法制备了 PDMS/SCF-Bolting Cloth (筛网)导电复合材料,其中筛网起到了降低复合材料导电渗流阈值和提高复合材料机械性能双重作用,导电渗流阈值低至0.06wt%。此外,通过控制筛网层数可获得单表面绝缘或者双表面绝缘的导电复合材料。通过添加少量纳米填料如超导炭黑粒子、石墨烯等可调节材料表面导电性能。
[Abstract]:Polymer based conductive composites are one of the most important polymer functional composites. They have wide application requirements in energy storage, battery electrodes, 3D printing materials, electromagnetic shielding, flexible displays, intelligent sensors and so on. Theory and practice show that the formation of a continuous and compact conductive filler network in the polymer matrix is the preparation of super high. The key to the conductivity of polymer matrix composites. The traditional method is generally by increasing the volume fraction of the conductive filler to the percolation threshold of the conductivity increase. Because the conductivity of the polymer matrix is very low, the conductive filler, such as carbon black particles, carbon fiber, is added to the insulating polymer matrix by adding large diameter ratio or large surface product. Flake graphite, carbon nanotubes and graphene are the focus of conducting conductive composites in polymer matrix at present. At present, there are three main methods of conducting conductive networks: self-assembly of conductive filler, double continuous phase method and phase separation method. Although the percolation threshold is reached, the percolation threshold is reached. The conductivity of the composite can be further increased by increasing the volume fraction of the filler, but the increase of the conductivity is very slow, but it causes a significant decrease in the material processing and mechanical properties. The main reason for the failure to further increase the conductivity lies in the average distance between the conductive filler and the conductivity of the composite material. In order to further improve the conductive properties of the composites, a method of constructing a conductive network to effectively reduce the average spacing of conductive particles is proposed in this paper. The space confinement force assembly (SCFNA) method is the core of the space confinement of the blends through mechanical means. The pressure and interface micro nano mechanical assembly, which exerts "forced assembly force" which is far larger than self assembly force, compelling "squeeze" the polymer between conductive particles to realize the compactness of the conductive network, which provides the possibility of greatly improving the conductivity. The main contents of this paper are as follows: 1, using this method, Two kinds of polymer matrix of thermosetting polymethylsiloxane (PDMS) and thermoplastic polypropylene (PP) are selected. Short cut carbon fiber (SCF) is selected as conductive filler. The conductive properties of the conductive composites, PDMS/SCF and PP/SCF., are only 0.45wt% and 3., which are higher than those of the traditional blending method, which are several times higher than those of the traditional blending method. 5wt%. has studied the effect of processing parameters, packing concentration, compression thickness and microstructural array on the conductive properties of composite materials. It is found that the compression thickness is an important factor affecting the conductivity of composite materials except the concentration of filler, especially at the high packing concentration. The property and performance enhancement potential.2, three element conductive composite materials are prepared by space restricted confinement assembly method, compared with graphene and superconducting carbon black particles. It is found that the conductive properties of the composite composite materials with multi wall carbon nanotubes and short cut carbon fibers are the best. At the same time, the processing mixing order of the three components obviously affects the electrical conductivity and the mechanical properties of the composites. The electrical properties and mechanical properties of the three components PDMS, (conductive carbon black) CCB, SCF mixed processing order, the conductivity and mechanical properties of PDMS/SCF/CCB composites are changed. The conductive properties of the composites prepared by PDMS and CCB blending before adding SCF blend are optimal, while SCF and CCB are mixed and then blended with PDMS to blend and blend. The mechanical properties of the composites prepared by the processing sequence are the best.3, and the PDMS/SCF-Bolting Cloth (sieve) conductive composite is prepared by the space confinement forced assembly method. The screen net plays a dual role in reducing the conductive percolation threshold of the composite material and improving the mechanical properties of the composite, and the conductive percolation threshold is lower to 0.06wt%.. The number of screen layers can be used to obtain conductive composites with single surface insulation or double surface insulation. By adding a small amount of nano filler, such as superconductive carbon black particles, graphene and so on, the conductive properties of the material can be adjusted.

【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB332

【参考文献】