THERMAL PROPERTIES OF CARBON NANOTUBESILICONE COMPOSITES

For many years, silicone has been widely used in applications such as sealants, adhesives, lubricants and medical implants, due to its favorable properties of good flexibility, low surface tension, excellent electrical properties, good weatherproofing ability, non-flammability, high gas permeability, as well as their stability toward heat and chemicals. However, unfilled silicone elastomer usually has poor mechanical and low electrical/ thermal conductive properties. Inorganic fillers such as fumed or precipitated silica, carbon black, boron nitride have normally been used to improve the above properties. Recently, carbon nanotube (CNT) has been used as a polymer composite filler due to its advantages of high aspect ratio resulting from nanometer diameter, and micron length and particularly high mechanical, electrical and thermal properties. The combined advantages of carbon nanotubes as a filler and silicone as a matrix may bring multifunctional properties such as high electrical/ thermal conductivity properties, high flexibility, thermal stability and chemical resistivity into this nanocomposite which is difficult to obtain using traditional inorganic fillers or other polymer matrices. This chapter describes the thermal properties of carbon nanotube-polymer composites and nanocomposites. A comprehensive literature review on this topic is presented which discusses different types of nanotubes (both single wall and multiwall) dispersed in polymers by different mixing procedures, which range from mechanical mixing, solution mixing with and without aid of sonication. Thermal behavior with a focus on a differential calorimetric study and thermal diffusivity of these nanocomposites has been dealt with in detail. The effect of concentration of nanotube in the polymer has been explored by studying the curing, glass transition (T_g), heat capacity (Δc_p) and crystallization behavior of the nanocomposites. The correlation of the change of thermal properties to the dispersion of CNT in polymer may be used to determine the quality of single wall carbon nanotube (SWCNT) dispersion in silicone polymer. Moreover, the thermal diffusivity of these composites (both single wall and multiwall nanotubepolymer composites) have been described with a view to investigate the potential application of these intricate materials as thermal interface material. Finally, the feasibility of deploying carbon nanotube-polymer composites as practical thermal interface materials for electronics thermal management is discussed.