Effects of Sodium Dodecyl Sulfate Concentrations on the Dispersion of Carbon Nanofibers in Water

摘要

The dispersion homogeneity of carbon nanofibers is one of the most critical problems in composite materials. Sodium dodecyl sulfate was used as the dispersant and homogeneously dispersed carbon nanofiber suspensions were obtained with sonication in this research. Five common measurements, namely the UV-visible spectrophotometer, transmission electron microscope, stewing-centrifugation method, zeta potential method and surface tension test, were used to characterize the homogeneity and stability of carbon nanofiber suspensions with different concentrations of sodium dodecyl sulfate. The dispersion mechanism was also discussed. Results show that the optimum concentration of sodium dodecyl sulfate in suspension is 1.6 g/L. The presence of SDS inhibits CNFs agglomeration effectively and only small-scale aggregates and tangles were observed, meanwhile the SDS adsorption film was formed on the CNFs surface, which decreased the surface tension and facilitated the homogeneous dispersion of CNFs in water. Moreover, the static repulsive force produced by sodium dodecyl sulfate ionizing and the steric repulsive force between the hydrophobic alkyl chains may overcome the van der Waals attractive force between the carbon nanofibers surface with the result of obtaining homogeneously dispersed carbon nanofibers.