Investigation On The Conductive Properties Of Carbon Nanotubes/Polymer Composites

Carbon nanotubes have unique structural and electrical properties. For carbon nanotubes/polymer composite materials, their excellent electrical properties are beneficial to increase electrical conductivity of the matrix, and improve the electrical conductive properties of the composites. Carbon nanotubes/polymer composite materials have been a research hot spot in the field of material physics. In this dissertation, the electrical conductive properties of carbon nanotube/polymer composite materials are studied systematically. And the electrical conductive model of carbon nanotube/polymer composites is proposed.The objective of this investigation is to supply theoretical guidance for carbon nanotubes/polymer composite materials applied to both electronic technology and nano electronic devices.Firstly, the structure and properties of carbon nanotubes and carbon nanotubes/polymer electrical conductive composites are introduced. The preparation methods of carbon nanotube/polymer composites, especially in the improvement of orderly arrangement and dispersion for carbon nanotubes in polymers, are reviewed systematically.The effects of electrical conductivity and mass fraction of carbon nanotubes as well as polymer, geometric parameters of carbon nanotubes, and the electrical tunneling effect due to a small region of the polymer matrix material filling the gap at the nanotubes junction on the electrical conductive properties of carbon nanotubes/polymer composites are discussed in detail. The overlapping contact configuration model of carbon nanotubes in polymer matrix is proposed. The electrical conductivity formula of the composites is deduced. The electrical conductive model of carbon nanotubes/polymer composites is also proposed.The electrical conductivity logarithms of multiwalled carbon nanotubes/phenoxy compositie and multiwalled carbon nanotubes/polyethersulfone composite are calculated numerically under different conditions. The simulate results show that when the mass fraction of carbon nanotubes is smaller than the percolation threshold values, the electrical conductivity of the composites increases with the increase of carbon nanotubes mass fraction, but the electrical conductivity is very small, which indicates that the electrical conductive property of the material is very weak when the mass fraction of carbon nanotubes is smaller than the percolation threshold values.The appropriate increase of the carbon nanotubes mass fraction can obviously improve the electrical conductive properties of the composites. And it is shown that there is a good semiconductive property for carbon nanotubes/polymer composite materials. The curvature degree of carbon nanotubes is an independent factor that affects the electrical conductivity of the composites. With the increase of carbon nanotubes curvature degree in the composites, the charge carrier transport capacity of the material becomes weak rapidly, which causes a evident decrease in the electrical conductivity of the material. For each composite, there is a critical value for the mass fraction of carbon nanotubes. When nanotubes mass fraction is larger than the critical value, the electrical conductivity of the composite would increase obviously with the mass fraction increasing, but the electrical conductivity would finally tend to a constant, namely there is a stable electrical network structure in the composite. The electrical conductivity of carbon nanotubes increases with the actual length of carbon nanotubes. Then, it may be said that the increase of carbon nanotubes in actual length reduces the contact resistance of the composites, which would be in favor of electrical conductivity of the material. In addition, the effects of carbon nanotubes actual length changing on the electrical conductive properties of the material is related to the type of polymer in the composite. The theoretical results are in agreement with the experimental phenomena observed by Jonas et al. The simulate results show that by improving the preparation process, and controlling the structure and parameters of the materials, electronic and electrical materials containing carbon nanotubes/polymer composites, with excellent properties as well as adjustable electrical conductivity, canbe made.