The Importance of Dilution Process and Solvent Selection on Particle Size Measurements - poster
Margaret Hwang, Jyo Lyn Hor, David Adrian
Dow, Dow Performance Silicones Process R&D, Midland, MI, USA
Dispersion of solids drives the product quality for filled materials such as liquid silicone rubber (LSR) and antifoam (AF) compounds; both are made by blending silica into a silicone matrix. An important indicator of filler incorporation is particle size. However, when using laser diffraction to size particles in diluted samples, the selection of solvent and the dilution process can affect the apparent particle size of silica. In this presentation, we highlight some considerations for selecting a suitable solvent for measuring silica particles in dilute solution. Because sufficiently high shear stress may break down agglomerates and lead to smaller apparent particle sizes, physical properties to consider include the viscosity of the solvent and the shear stress imposed on the system during the dilution process. On the other hand, interactions between the solvent and the particles or between the solvent and the matrix can either lead to agglomeration or further dispersion of particles. Therefore, when a product is changed significantly, it is necessary to evaluate whether the current dilution and solvent combination is able to capture those changes.