Optimisation and analysis of bead milling process for preparation of highly viscous, binder-free dispersions of carbon black pigment

Lab scale milling equipment is often employed to prepare dispersion formulations that possess considerably different characteristics from each other. The viscosity of a pre-mixed dispersion is one of the main parameters to consider when selecting a particular milling equipment for grinding of pigment. Generally, high viscosity dispersions are not easy to grind using a lab-scale re-circulating bead mill. There are numerous factors that can potentially result in changes in the starting point formulations. It is therefore crucial to assess any variations in the pigment loading occurring during milling for extended time periods. In this study, rheological characterisation, thermogravimetric analyses and surface resistivity measurements have been carried out on multiple dispersion formulations and it is shown that pigment loading after milling can be different from that in the starting point formulation.