Synergistic effect in conductive networks constructed with carbon nanofillers in different dimensions

Abstract

Abstract. Herein, investigation on synergistic effect during network formation for conductive network constructed with carbon nanofillers in different dimensions is conducted. Multi-walled carbon nanotubes (MWNTs) and carbon black (CB) are employed as conductive fillers in this system. Morphological control of the conductive network is realized by adjusting the ratio between different fillers. Classical percolation threshold theory and adjusted excluded volume theory are used to analyze the electrical percolating behavior of these systems. It is observed that the percolation threshold of hybrid fillers filled conductive polymer composites (CPCs) is much lower than that of MWNTs or CB filled CPCs, and it can be reduced from 2.4 to 0.21 wt% by replacing half of the MWNTs with CB. Possible mechanism of this phenomenon is discussed together with morphological observation. A model is proposed to understand the mechanism of the percolation behavior in the composites containing various proportions of nanofillers. Our work is important for the design and preparation of low cost conductive polymer composites with novel electrical property. Vol.6, No.2 (2012) 159-168 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2012.17 * Corresponding author, e-mail: huadeng@scu.edu.cn © BME-PT PE/MWNTs composites prepared by melt blending. The value is often between 1 to 5 wt% for melt compounded systems and considered as statistical percolation threshold [22]. The mechanism behind this significant difference between kinetic and statistical percolation is the prohibition of re-aggregation between CNTs during melt compounding process [22,24]. It was reported that the re-aggregation process of CNTs within polymer melt can take hours to complete [25]. To achieve better conductivity or lower cost, more than one kind of filler, particularly fillers in different aspect ratios, are used to prepare CPCs. Regarding the formation of conductive network with fillers in different aspect ratios, theoretical study has shown that it is not necessary to build conductive network with high aspect ratio filler alone [26], and the percolation threshold is sensitive to the portion of high aspect ratio filler in a system containing fillers in different aspect ratios [27]. There are a number of investigations reported in the literature on mixed carbon fillers filled CPCs [26,[28][29][30][31]. However, the percolation thresholds of these systems filled with mixed fillers are only simple average of that for systems filled with a particular kind of carbon filler. Therefore, more study is needed to study the true synergistic effect between conductive fillers of different dimensionality in building conductive network. In current study, CPCs based on mixed filler between carbon nanofillers in different dimensions and polypropylene will be fabricated. It is well known that polyolefin is a widely used material and its processability is prominent. Moreover, due to the difference in filler dimension and intrinsic structure, the networ...

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