High electrical conductivity waterborne dispersions of carbon black pigment

The carbon black grades that are employed as pigments in printing inks are characterised by low surface area, low structure and a higher proportion of chemisorbed polar groups on the surface. All of these features render the pigment easily dispersable - a property crucially important in the case of printing inks. However, high electrical conductivity of carbon black is known to be possessed only by the grades that have high surface area, high structure and lower proportion of polar groups, and consequently poor dispersability. The study reported here aimed to resolve such a dilemma between high electrical conductivity and poor dispersability. Thus, novel methodologies were developed to prepare waterborne, binder-free dispersions based on "non-printing ink" grades of carbon black. The particle size analysis, rheological characterisation, sedimentation analyses and electrical characterisation results clearly indicate that the selected pigment grades of carbon black were successfully stabilised as dispersions that possess high electrical conductivity at considerably lower pigment loadings than normal.