{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Thermal properties and percolation in carbon nanotube-polymer

Thermal properties and percolation in carbon nanotube-polymer

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Thermal properties and percolation in carbon nanotube-polymer composites P. Bonnet, D. Sireude, B. Garnier, and O. Chauvet a Institut de Matériaux Jean Rouxel, UMR 6502 and Laboratoire de Thermocinetique de Nantes, UMR 6607 CNRS—Universite de Nantes, BP 32229, 44322 Nantes cedex 3, France Received 7 September 2007; accepted 25 October 2007; published online 14 November 2007 Thermal properties of single walled carbon nanotube SWNT /polymethylmetacrylate composite thick films have been investigated at room temperature. The introduction of 7% SWNT into the polymer matrix enhances the thermal conductivity of the composite by 55% while the electrical conductivity increases by several orders of magnitude. Despite this difference, we show that the moderate enhancement of the thermal conductivity is quantified by the percolation of the SWNT network. A thermal conductivity of the SWNT network of 55 W/m K is estimated. © 2007 American Institute of Physics . DOI: 10.1063/1.2813625 The unique physical properties of single walled carbon nanotubes SWNT suggest important mechanical reinforce- ment and electrical or thermal conductivity enhancement of SWNT based composites, of interest for potential applications. 1 3 In the case of thermal properties, the en- hancements are often less than expected 4 or from what can be extrapolated from the electrical transport properties. The quality of the SWNT dispersion in the matrix and the homo- geneity of the composite or tube purity may be responsible for these poor properties. 5 More fundamental reasons are also evoked such as the role of Kapitza contact resistances or tube-end transport. 6 There is still a debate whether the en- hancement should be described within the percolation concept 7 , 8 or by making use of effective medium approaches. 9 In this paper, we investigate the thermal properties of SWNT/polymethylmetacrylate PMMA composites. The thermal conductivity of the composites increases by 55% for 7% SWNT loading. This enhancement is described within the percolation concept and its rather low magnitude comes from the intrinsic thermal conductivity of the SWNT net- work which is found to be close to 55 W/m K. The SWNT/PMMA nanocomposite films have been ob- tained with nanotubes produced by electric arc discharge GDPC, Montpellier and polymethylmetacrylate Aldrich, MW: 120 000 g/mol . Raman spectroscopy shows that the average tube diameter is close to 1.5 nm. The SWNTs are dispersed in dimethylformamide DMF 0.75 mg/ml and sonicated for 2 h. The dispersion is mixed with PMMA and the SWNT/PMMA ratio is adjusted for a final SWNT vol- ume fraction f in the solid phase between 0.1% and 7.4% assuming that DMF is fully removed and that the films are dense. The mixture is sonicated for 2 h and stirred for ho- mogenization at 50 °C. This treatment increases the viscos- ity of the dispersion which, in turn, limits the SWNT aggre- gation before the solvent evaporation. The DMF evaporation occurs at 120 °C under primary vacuum followed by a post annealing at 140 °C for 48 h in order to completely remove the solvent, as confirmed by thermogravimetric analysis.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}