Single-wall carbon nanotube-polymer nanocomposites: Fabrication, processing, morphology, and properties
Since their discovery more than two decades ago, carbon nanotubes have attracted considerable attention and generated intense research activities. The interest in this extraordinary carbon form is based on their unique combination of nanometric dimensions, electronic structure, and chemical composition that result in exceptional thermal, electrical, mechanical and optical properties, which makes them very promising nanofillers for multifunctional nanocomposites. Despite the extensive research on nanotube-polymer nanocomposites throughout the world, the predicted and envisioned superior composite properties have only been partially realized. In this dissertation, we investigate the influence of composite key parameters on resulting properties to gain a better understanding of these novel nanostructures. Single-wall carbon nanotubes were dispersed in amorphous polystyrene and semicrystalline nylon 66 and polyethylene by the use of specifically developed fabrication methods. Resulting nanocomposites were melt-spun into fibers or hot-pressed to films and sheets. A wide variety of characterization methods was applied to thoroughly describe the composite morphology and properties. The fabrication methods result in good SWNT dispersion which was determined by optical microscopy and SEM. Exceptional SWNT alignment in composites is achieved by melt-fiber spinning of SWNT - polyethylene composites. Polarized Raman spectroscopy showed that the alignment increases with increasing extensional flow during melt-fiber. A combination of crystallization and x-ray scattering studies showed that SWNT nucleate the polyethylene crystallization and template the crystal growth of the semicrystalline matrix. Mechanical properties of composite fibers increase with increasing SWNT loading and alignment; e.g. the elastic modulus of 20 wt% SWNT - polyethylene fiber increases up to 450% relative to polyethylene fibers. The electrical conductivity critically depends on the aspect ratio of the SWNT as the formation of a percolating nanotube network in composites occurs at lower nanotube loadings as the aspect ratio increases. Finally, thermal conductivity in SWNT - polyethylene composites depends on SWNT loading and polyethylene crystallinity. Composites with 30 wt% nanotubes in high density polyethylene have a thermal conductivity twice as high as a low density polyethylene composite of the same SWNT loading.
Haggenmuller, Reto, "Single-wall carbon nanotube-polymer nanocomposites: Fabrication, processing, morphology, and properties" (2005). Dissertations available from ProQuest. AAI3197681.