尼龙6导电复合材料的结构控制与性能研究

发布时间：2018-05-07 23:25

本文选题：导电聚合物复合材料 + 电磁屏蔽　；参考：《中北大学》2017年硕士论文

【摘要】：随着电子科技及信息技术等领域的飞速发展,导电聚合物复合材料在功能材料中占有举足轻重的位置。该类复合材料加工性能好、电阻可调节、成本低、可设计性强,广泛应用在能源、运输、电子电器等领域。探索新方法制备具有高性能低成本的导电聚合物复合材料以及实现其在电磁屏蔽领域的应用是目前导电功能材料领域尤为重要的研究课题。本课题通过碳纤维、膨胀石墨两种导电填料对尼龙6进行改性,并通过对导电网络结构进行控制,得到了性能优异的尼龙6导电复合材料。主要研究结果如下:(1)通过简单熔融共混制备了PA6/EG复合材料,随着热膨胀石墨的加入,导电粒子之间形成的导电、导热网络越来越完善,得到了一种拥有优异导电、导热以及电磁屏蔽性能的复合材料。当添加9.09vol%EG时材料的电导率达到0.262S/m,其导热系数也达到最佳,为1.0202W/m·K,电磁屏蔽性能达到23dB。同时,EG的加入可以为复合材料提供更多的异相成核点,提高了复合材料的结晶温度与结晶度,结晶度最高提高了26.98%。因此PA6/EG复合材料的动态储能模量大幅度提高,并且填料的加入对聚合物分子链有限制作用,复合材料的玻璃化转变温度也大幅度提高。(2)通过在PA6和EG熔融共混过程中加入CF,改变两种填料的比例制备了复合材料,结果表明CF对复合材料的增强作用特别明显,相比纯PA6,复合材料的拉伸、弯曲性能均有大幅提高。当CF的质量分数为20%时,PA6/EG/CF复合材料拉伸强度、拉伸模量、弯曲强度、弯曲模量最佳,可达到100.8 MPa,4.67 GPa和95.7 MPa和6.42 GPa,相比纯PA6分别提高了41.69%、81.01%和86.55%,293.87%。EG的加入有利于复合材料导电、导热以及电磁屏蔽性能的提高。添加20wt%EG时材料的电导率最高,达到0.262S/m,导热系数可达1.3379W/m?K,电磁屏蔽性能也可达到20dB的应用要求。并且EG和CF粒子在尼龙6基体中有异相成核作用,晶核生长速率增加,结晶更加容易,从而提高尼龙6复合材料的结晶温度。并且随着EG比例增加,结晶度先增大后减小。(3)通过高速机械共混-模压成型制备了EG、CF两种不同填料的隔离结构PA6复合材料,其导电逾渗值明显降低,达到了我们预期想要的结果。PA6/EG体系的逾渗值为0.134 vol%,PA6/CF体系的逾渗值为1.9 vol%。并且当填料含量增加时,在复合材料中构建了完善的导电网络,使得复合材料在导热、电磁屏蔽、动态力学等方面也得到优异的性能。并且对于隔离结构PA6/CF复合材料来说,复合材料的屏蔽效能在8.2~12.4 GHz范围内的都是随着频率的增大先上升,出现特征峰值后又下降。且随着CF含量的增大,特征吸收峰值不断增大。并且随着CF含量的增加出现特征峰的频率向高频移动。(4)通过在隔离结构PA6/EG复合材料制备过程中添加一定量的CF制备的串联隔离结构的PA6/EG/CF复合材料,微观结构可以看出CF作为EG隔离导电网络的桥梁,使得导电网络更加完善,形成了一种类似“糖葫芦”状的结构。对比了三种长度的CF制备的串联隔离结构PA6/EG/CF复合材料的导电、电磁屏蔽、动态力学等方面性能发现,这三种长度的CF制备的复合材料的逾渗值分别为0.31 vol%、0.325 vol%、0.241vol%。通过100μm碳纤维制备的这种复合材料的各方面性能最优,5mm碳纤维制备次之,700μm碳纤维制备相对较低。
[Abstract]:With the rapid development of electronic technology, information technology and other fields, conductive polymer composites occupy an important position in functional materials. This kind of composite has good processing performance, adjustable resistance, low cost and strong design. It is widely used in the fields of energy, transportation, electrical appliances and so on. The new method has high performance and low performance. The cost of conductive polymer composite and its application in the field of electromagnetic shielding are the most important research topics in the field of conductive functional materials. This topic is modified by two kinds of conductive filler of carbon fiber and expanded graphite, and through the control of the structure of the conductive network, the nylon 6 with excellent performance is obtained. The main research results are as follows: (1) PA6/EG composites are prepared by simple melting and blending. With the addition of thermal expanded graphite, the conduction between conductive particles and the heat conduction network are becoming more and more perfect. A composite material with excellent conductivity, heat conduction and electrical and magnetic shielding properties is obtained. When 9.09vol%EG is added, the material is added to the material. The conductivity reaches 0.262S/m, its thermal conductivity is also the best, it is 1.0202W/m K, the electromagnetic shielding performance reaches 23dB.. The addition of EG can provide more heterogeneous nucleation points for the composite materials, improve the crystallization temperature and crystallinity of the composites, and the highest crystallinity increases the dynamic storage modulus of 26.98%. and thus the PA6/EG composite. The addition of the filler has a limited effect on the polymer molecular chain and the glass transition temperature of the composite increases greatly. (2) the composite is prepared by adding CF in the melt blending process of PA6 and EG and changing the proportion of two kinds of filler. The results show that the enhancement of the composites is particularly obvious, compared with pure PA6, When the mass fraction of CF is 20%, the tensile strength, tensile modulus, bending strength and flexural modulus of PA6/EG/CF composites are the best, which can reach 100.8 MPa, 4.67 GPa and 95.7 MPa and 6.42 GPa, compared with pure PA6 by 41.69%, 81.01% and 86.55% respectively. The addition of 293.87%.EG is beneficial to the composite. The electrical conductivity, heat conduction and electromagnetic shielding performance of the material are improved. When adding 20wt%EG, the material has the highest electrical conductivity, up to 0.262S/m, the thermal conductivity can reach 1.3379W/m? K, the electromagnetic shielding performance can also reach the application requirements of 20dB. And EG and CF particles have heterogenous nucleation in the nylon 6 matrix, the growth rate of crystal nucleus is increased, and the crystallization is easier. Thus, crystallization is more easy to extract and thus extract The crystallization temperature of the high nylon 6 composite was increased and the crystallinity increased first and then decreased with the increase of EG ratio. (3) the isolated structure PA6 composites of two different fillers were prepared by high speed mechanical blending and molding, and the percolation value of the.PA6/EG system decreased significantly, and the percolation value of the.PA6/EG system we expected was 0.134 Vo L%, the percolation value of the PA6/CF system is 1.9 vol%. and when the filler content is increased, a perfect conductive network is constructed in the composite material, which makes the composite excellent performance in heat conduction, electromagnetic shielding, dynamic mechanics and so on. And for the isolation structure PA6/CF composite material, the shielding effectiveness of the composite material is 8.2~12.4 GHz With the increase of the CF content, the peak value of the characteristic absorption increases with the increase of the content of the CF. (4) a certain amount of CF in series is added to the isolation structure of the PA6/EG composite material. The microstructure of PA6/EG/CF composite material, the microstructure can be seen as a bridge of CF as the EG insulation network, making the conductive network more perfect, forming a kind of "sugar gourd" like structure. Compare the conductivity, electromagnetic shielding, dynamic mechanics, and other aspects of the series isolated structure PA6/EG/CF composite prepared by three kinds of CF It is found that the percolation values of these three CF composites are 0.31 vol% and 0.325 vol% respectively. The properties of the composites prepared by 0.241vol%. by 100 mu m fiber are the best, the 5mm carbon fibers are prepared second, and the 700 um m carbon fiber is relatively low.

【学位授予单位】：中北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332

【参考文献】