Fast NMR relaxation, powder wettability and Hansen Solubility Parameter analyses applied to particle dispersibility

• Published in: Powder technology 2021-01, Vol.377, p.545-552
• Main Authors: Fairhurst, David, Sharma, Ravi, Takeda, Shin-ichi, Cosgrove, Terence, Prescott, Stuart W.
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum oxide; Dispersibility; Intermolecular forces; Manufacturability; NMR; Nuclear magnetic resonance; Solubility; Solubility parameters; Solvent selection; Solvents; Structural stability; Wettability; Zinc oxide
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2020.09.002

The selection of appropriate solvents into which inorganic and organic sub-micron particles can be dispersed is important for product manufacturability and performance. Molecular-level interactions determine solvent suitability but are difficult to measure; existing experimental approaches require slow/expensive tests of dispersion stability. Solvent relaxation NMR 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 stability measurements. 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. Suitable solvents can be selected from a database of HSP values, and solvents can be blended to match the particle interface. The application of the approach is illustrated using a range of surface modified zinc oxide and aluminum oxide particles, with similarities and differences between the particle surfaces becoming evident through the analysis. [Display omitted] •Describes new, fast, robust method for determining solvents for dispersing particles.•Solvent relaxation NMR reveals suitable solvents & predicts other suitable solvents.•Proposes a normalized relaxation number that correlates with wetting of particles.•Founded on well-known Hansen Solubility Parameter analysis for selecting solvents.