The Effect of Dispersion Quality of Carbon Nanotube Colloids on Physical Properties of Nanocomposites

Carbon nanotubes have been shown to be excellent nano size filler material in dozens of different matrices. They possess many physical features that make them almost optimal for this purpose including high electrical conductivity, mechanical strength and thermal conductivity. There is however one property that makes nanotubes challenging to use; they typically come in aggregates which have high internal binding energies. Therefore in order to generate evenly distributed dispersions one need to use high shear forces and some times chemical modification of the tubes. These process conditions can cause changes in an integrity of the tubes themselves and inhibit the matrix-filler and filler-filler interactions diminishing the physical properties of the nanocomposites.

The main objectives of this thesis were to answer how the development of the dispersion quality of aqueous nanotube colloids can be optimized and monitored during sonication assisted dispersion, how the dispersion quality affects the properties of the nanocomposites, and how the properties can be further improved after composite have already been prepared.

It was observed that depending on the expected feature, maximum dispersion quality is not always needed and one can even benefit from residual pristine fillerfiller interaction of the nanotube agglomerates. Another observation was that if surfactants are being used especially in aqueous dispersion to stabilize the colloid, they have inhibiting effect on properties of the solution casted composites by lowering the filler-filler and filler-matrix interaction. By removing the surfactant afterward some of these expected properties can be realized.