Conductive thermoplastic multi-walled carbon nanotubes/copper nanowires/polystyrene hybrid nanocomposites
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2012
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Abstract
Conductive polymer nanocomposites have drawn much interest for the last decade in its versatility and novel applications. Because of the increased surface area of the fillers, properties such as Electrostatic Discharge (ESD), Electromagnetic Interference (EMI) shielding and possibly mechanical properties can be enhanced tremendously and they are used in many light weight hand held electronics. To increase the competitiveness of nanocomposites, percolation threshold should be minimized so as to lower the production cost. In this project, the goal is to use as little as possible nanofillers in polymer composites and still benefit from their favourable properties. It was discovered that, by adding a small amount of second filler, the overall conductivity and EMI shielding effectiveness can be enhanced and reached an optimum level. The resulted MWNT/CuNW/Polystyrene composites exhibit EMI shielding effectiveness exceeding that of metal nanofillers and carbon nanotube/polymer composites formulated by solution processing.
There are three major mechanisms for EMI shielding namely reflection, absorption and multiple reflections. From literature reviews of the mechanism of EMI shielding, MWNT shields mainly by adsorption while metal nanowire shields largely by reflection. Inherently, these two different fillers have very distant physical properties, and studying the synergy effect of these two fillers in polystyrene as conductive composites is part of the objective of this project.
The objective of this project 1s satisfied by making an extremely low percolated MWNT/PS nanocomposite with a volume fraction of only 0.00052. This is the lowest concentration being reported from the literature review. By altering the ratios and concentrations of the two nanofillers (MWNT and CuNW) in polystyrene composites, an optimum ratio of 3: 1 is obtained. In this ratio, the hybrid nanocomposites prepared have the highest electrical conductivity and EMI shielding effectiveness. The statistical analysis agrees well with the previous findings that the amount of MWNT in the polymer is the major factor affecting the overall electrical conductivity of final composites. The other factors studied are sonication time, compression pressure, time and temperature which are not significant to change the electrical conductivity of the composites.
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Bibliography: p. 25-27, 43-45, 60-62, 72-73
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Chau, J. (2012). Conductive thermoplastic multi-walled carbon nanotubes/copper nanowires/polystyrene hybrid nanocomposites (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/4835