Structural characterization and electrical properties of carbon nanotubes/epoxy polymer composites (original) (raw)
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Spectroscopy Letters
The main objective of this work was to study the electric response of the carbon nanotubes/epoxy composites upon varying the concentrations of the nanotubes, in order to obtain a comprehensive understanding of the influence of filler's percentage and temperature on the impedance parameters. Dielectric spectra of the carbon nanotubes-epoxy resin composites were recorded in the frequency range of 1 Hz-10 MHz and over the temperature range of 25°C-105°C. In a first part, the thermal properties of the composites were analyzed by differential scanning calorimetry, which reveals a decrease in the glass transition temperatures with the concentration of the nanotubes. The phenomenon of the positive temperature coefficient in resistivity that is recognizable for the carbon nanotube concentrations above the percolation threshold has been the interest of the second part of the work. The results reveal that gradually, as the filler concentration approaches the percolation threshold of the composite, the positive temperature coefficient in the resistivity effect becomes even more pronounced. Finally, the structure of the filled polymer samples is characterized using a small angle neutron scattering technique.
Composites Science and Technology
A study of the ac electrical transport properties of a diglycidyl ether of bisphenol A-based epoxy resin (DGEBA) polymerized with a diethylene triamine (DETA) and reinforced with single wall carbon nanotubes (SWNTs) is presented. The main objective is the investigation of the particular electrical behavior of the conductive filler in the composite and the development of new nanocomposite materials based on epoxy resins with controlled structural and electrical properties. The structural and electrical characterization of the SWNT-DGEBA/DETA hybrid system, performed by differential scanning calorimetry, Raman and ac impedance spectroscopy show interesting effects, including the particular interaction between the polymer and nanotubes, the tendency of the nanotube structure to increase the rate of reaction and substantial effects of the nanotube bundle conformation, dependent on matrix intercalation, on the dielectric behavior of the composite. #
Dielectric behavior of epoxy matrix/single-walled carbon nanotube composites
Composites Science and Technology, 2004
A study of the ac electrical transport properties of a diglycidyl ether of bisphenol A-based epoxy resin (DGEBA) polymerized with a diethylene triamine (DETA) and reinforced with single wall carbon nanotubes (SWNTs) is presented. The main objective is the investigation of the particular electrical behavior of the conductive filler in the composite and the development of new nanocomposite materials based on epoxy resins with controlled structural and electrical properties. The structural and electrical characterization of the SWNT–DGEBA/DETA hybrid system, performed by differential scanning calorimetry, Raman and ac impedance spectroscopy show interesting effects, including the particular interaction between the polymer and nanotubes, the tendency of the nanotube structure to increase the rate of reaction and substantial effects of the nanotube bundle conformation, dependent on matrix intercalation, on the dielectric behavior of the composite.
Journal of Macromolecular Science, Part B, 2018
The electrical properties of epoxy polymer/carbon nanotubes composites were characterized using impedance spectroscopy in the frequency range between 1 Hz and 10 MHz and temperature range between 25 C and 105 C. We report the analysis of the experimental data using the electric modulus formalisms to understand the dielectric relaxation mechanisms. The variation of the real and imaginary parts of the electric modulus versus frequency and temperature were suggestive of two relaxation processes, associated with dipolar relaxation and CNT-polymer interfaces. The Havriliak-Negami model of dielectric relaxation was used for modelling the relaxation processes, extracting the relaxation parameters.
Dielectric Spectroscopy and Tunability of Multi-Walled Carbon Nanotube/Epoxy Resin Composites
The dielectric response of oxidized multi-walled carbon nanotube / epoxy resin composites, is investigated with respect to filler content concentration, over a wide temperature and frequency range. Specimens, below the percolation threshold, exhibit similar behaviour to that of the neat epoxy. Two relaxation modes are observed in the low temperature region, attributed to the re-arrangement of small parts of the polymer chain (γ-mode) and the reorientation of polar side groups (β-mode) respectively, where in the high temperature region the evolution of the α-mode is present. Direct current (DC) conduction follows the Vogel -Tamann -Fulcher equation as expected. The dielectric response of specimens, above the percolation threshold, follows the "Random Free Energy Barrier Model". DC conductivity exhibits Arrhenius temperature dependence with two distinct regions. The activation energies of both regions were evaluated. The contact resistance between two adjacent carbon nanotubes was also calculated. The effective dielectric constant as well as the capacitance of the specimens, above the percolation threshold, can be modulated by means of an applied DC bias voltage.
Effect of Carbon Nanotubes on the Electrical Properties of the Polymeric Composites
Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference
Experimental study of single-wall carbon nabotubes (CNT) effect on the electrical properties of polymeric composite materials based on epoxy matrix has been carried out. Direct-current (DC) as well as alternating-current (AC) electrical conductivity of nanocomposites with different CNT concentrations have been investigated in the temperature interval from 293 K to 373 K. Measurements of Seebeck coefficient confirm n-type conductivity of composite with CNTs. Percolation threshold of the composite material under study has been estimated. It has been found that addition of single-wall CNT at low concentration causes hysteresis of current-voltage characteristics and the temperature dependences of electrical conductivity as well as its anisotropy in the samples under study. No noticeable frequency dependence of the AC electrical conductivity has been found in the frequency range from 100 Hz to 300 kHz.
Applied Microscopy
The dielectric relaxation characteristics of composites with different concentrations of carbon nanotubes loaded in an epoxy polymer matrix has been studied as a function of frequency over a wide range (1 Hz~10 MHz) at room temperature. Two characterization techniques were used in this work to measure and calculate the dimensionality parameters: small angle neutron scattering and impedance spectroscopy. The results obtained from both methods are in good agreement, indicating the reliability of the estimated fractal dimension, despite of the difference in the length scales accessed by the two techniques.
Polymer, 1999
To avoid electrostatic charging of an insulating matrix an electrical conductivity above s 10 Ϫ6 Sm Ϫ1 is needed. At present, the most common practice to achieve this conductivity is to use a conductive filler such as carbon black. In this work, untreated catalytically-grown carbon nanotubes were dispersed in an epoxy matrix. After curing the epoxy, the electrical properties of the composite were measured in order to relate the filler volume fraction to the electrical conductivity. The intense stirring process used to disperse the carbon nanotubes has made it possible to achieve a matrix conductivity around s 10 Ϫ2 Sm Ϫ1 with filler volume fractions as low as 0.1 vol.%. These figures represent an advance on best conductivity values previously obtained with carbon black in the same epoxy matrix. These low filler fractions ensure that the mechanical properties of the matrix are not compromised.
Dielectric behaviour of carbon nanotubes particles-filled polyester polymer composites
This paper reports the dielectric relaxation studies of carbon nanotubes loaded in polyester polymer matrix. The study was carried out in the frequency range between 100 Hz and 1 MHz at constant temperature, T ¼ 300 K. The frequency dependence of the electrical data was treated in the frameworks of the impedance Havriliak-Negami formalism and by using the universal Jonscher power law. The imaginary and real parts of the dielectric permittivity change with concentration of the carbon nanotubes. This work consists in studying the influence of these nanoparticles on the dielectric properties, describing the electrical relaxation and the conduction mechanisms.
Nanocomposites based on polymer matrix and carbon nanotubes as studied by dielectric spectroscopy
In this review work, the use of dielec. spectroscopy as a tool for analyzing elec. and dielec. properties of different nanocomposites based on both thermosetting or thermoplastic polymer matrixes and carbon nanotubes (CNTs) is reviewed. The insulator-to-conductor transition (percolation threshold) of the nanocomposites, as found by several authors, is presented for a wide variety of nanocomposites. The application of the percolation theory and its power laws to those nanocomposites is presented as carried out by several authors, together with the theor. parameters obtained for different types of nanocomposites. Meaningful explanations of the obtained parameter values are given for each system. The effect of filler amt. and/or chem. modification on the properties and theor. parameters is presented. The effect of CNTs on the mol. dynamics of the polymer matrix is also reviewed as reported by several authors.