Aqueous carbon black dispersions stabilized by sodium lignosulfonates

Six different sodium lignosulfonates with varying degrees of sulfonation (0.14–1.29 sulfonate groups per phenylpropane unit) and molecular weights (Mw = 6000–330,000 g/mol) were evaluated for their ability to disperse carbon black in aqueous media. Rheological and particle size measurements of carbon black dispersions indicated that lignosulfonates with low degree of sulfonation function as good carbon black dispersants. The dispersion efficiency did not correspond directly to the amount of lignosulfonate adsorbed on the surface of carbon black. The lignosulfonates have an ability to enhance the colloidal stability by electrostatic repulsion, and the likely mechanism of stabilization is a combination of electrostatic repulsion and steric hindrance.