Thermal behavior of single-walled carbon nanotube polymer-matrix composites

Single-walled carbon nanotube (SWNT)-poly(vinylidene fluoride) (PVDF) composites were fabricated by dispersion of SWNT in an aqueous surfactant solution, followed by mixing with PVDF powder, filtration and hot pressing. The thermal properties of the composites at various SWNT volume fraction up to 49% were investigated. The coefficient of thermal expansion (CTE) was decreased with increase of the SWNT content. The thermal conductivity increased with temperature in the temperature range from 25 to 150 degrees C. The thermal conductivity was enhanced, but not up to the level required by heat sink applications. The melting point was not affected significantly by the addition of SWNT, but the degree of crystallinity was increased and the decomposition temperature of the matrix was decreased. The large number of junctions among SWNT largely offsets the benefit of the high thermal conductivity of SWNT. In addition, the impurity and defects in SWNT are believed to limit the thermal conductivity of the composites. Lastly, the reduced thermal stability of the composite compared to the matrix might result from the presence of the metal catalyst contained in the SWNT. (C) 2005 Elsevier Ltd. All rights reserved.