A comparison of melt and solution mixing on the dispersion of carbon nanotubes in a poly(vinylidene fluoride) matrix

Multi-walled carbon nanotube (MWCNT)/poly(vinylidene fluoride) (PVDF) composites were prepared by two frequently-used approaches, melt and solution mixing. The dispersion state of MWCNTs in the PVDF matrix was evaluated by rheological properties and confirmed by optical microscope, scanning electron microscope and transmission electron microscope images. It was found that the dispersion state of MWCNTs was dependent not only on the concentration of MWCNTs but also the mixing method. Specifically, solution mixing led to a much better dispersion of MWCNTs than melt mixing at low concentrations of MWCNTs (less than 5 wt.%), while the situation was reversed at higher concentrations. The dispersion mechanisms of MWCNTs for the two mixing methods were also discussed.