Investigation of epoxy resin/multiwalled carbon nanotube nanocomposite behavior at low frequency
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Patrizia Savi, Muhammad Yasir, Mario Miscuglio, and Muna Hajj Yahya Department of Electronic and Telecommunication, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy
Alberto Tagliaferro Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino 10129, Italy (Received 7 July 2014; accepted 14 October 2014)
In this work, the electrical characterization of nanocomposites made of epoxy resins with multiwalled carbon nanotubes is presented. As the filler, two different types of multiwalled carbon nanotubes with different aspect ratios (280, 1250) and defectiveness were selected. The production procedure, the morphological characterization, the I–V DC characteristics, and the low frequency complex permittivity (in the range 100 kHz–12 MHz) of these nanocomposites are discussed. To investigate the dispersion of the solution, a study which linked the mixing time to the zeta potential was performed. The experimental results show that with the same matrix and by using the same measurement techniques, the two nanocomposites give different results and can be correlated with the characteristics of nanotubes. The dc conductivity of the nanocomposites was measured by means of a two-point probe technique. The conductivity in the frequency range 100 KHz–12 MHz was evaluated using a circular disk capacitor and measuring the impedance. The measured conductivity follows a percolation scaling law of the form r } (p pc)t. A best fit to the measured conductivity data was obtained and the values of the exponent t compared to those in the literature.
I. INTRODUCTION
Recent years have seen a significant research increase in development activities on nanocomposites (NCs) for engineering applications. Polymer NCs, especially those containing carbon nanotubes (CNTs), have proved to be particularly attractive, as the addition of CNTs leads to electrically conductive composites with enhanced structural characteristics. Multiwalled CNTs (MWCNTs) are the most commonly used for large-scale applications because of their affordable cost (see e.g., Ref. 1 and 2). Their extraordinary properties are easily transferred to the host polymer thus improving the properties of the NC. For example, MWCNTs are frequently used as a reinforcement for polymers,3,4 since CNTs are much stronger and have a much larger aspect ratio (i.e., the ratio between length and diameter) than conventional carbon fibers. Alternatively, CNTs have been embedded into polymers or other media to obtain materials with good electrical and thermal properties.5,6 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.348
The main advantage of MWCNTs is that only a few weight percentage (wt%) of them can greatly improve the properties of the hosting material from the mechanical and electrical point of view.6 The fall in production costs and the consequent increase of their availability have also made MWCNTs interesting filler materials for large-scale applications.7 In an in
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