Using NMR solvent relaxation to determine the Hansen solubility parameters of a carbon black and as a quick method to compare the surface quality of carbon blacks

Abstract

The selection of appropriate solvents into which carbon blacks can be dispersed optimally is important for product manufacture and performance. Molecular-level interactions determine solvent suitability but are difficult to measure; existing experimental approaches require slow/expensive tests of dispersion stability. NMR solvent relaxation measurements are shown to be a fast indicator of solvent suitability, with sensitivity to the solvent-particle intermolecular forces making it a reliable proxy for determining optimum dispersibility. A structured approach to relaxation measurements with a selection of both good and poor solvents yields the Hansen solubility parameters (HSP) for the particle surface. Once obtained, suitable solvents (or solvent mixtures) can be selected from a database of HSP values to match the particle interface. The application of the NMR solvent relaxation approach for determining the HSP values is illustrated for a commercially available carbon black. Furthermore, individual solvent relaxation data for two solvents (e.g., hexane and IPA) with a variety of carbon blacks may be plotted against each other to highlight differences in surface chemistry. Using this approach, results are compared, for the first time, with data from inverse gas chromatography (IGC) with a relatively similar outcome. NMR solvent relaxation analysis provides a quick, facile, and cost-effective methodology to identify the replacement of both powder and solvent raw materials.Graphical