Size distribution of migrating particles and droplets under gravity in concentrated dispersions measured with static multiple light scattering.

Hypothesis: Light scattering techniques can provide a non-intrusive measurement of particle and droplet size distribution but are limited to relatively diluted liquid dispersions. Measurement of particle velocity distributions (PVD) and particle/droplet size distributions (PSD) in diluted to highly concentrated solid suspensions and emulsions can be performed by coupling the static multiple light scattering technique (SMLS) to mathematical models describing the vertical motion under gravity of polydisperse particles and droplets.

Experiments: Measurement of the PSD using SMLS was performed on silica particles dispersed in water with monomodal, bimodal and trimodal PSDs ranging from 570 nm and 7.90 µm. Quasi-monodisperse certified latex particles with 815 nm mean diameter dispersed in water and non-controlled emulsions of hexadecane-water emulsions at volume fractions ranging from 0.005 % to 20 % were also characterized with SMLS. These measurements were compared to certified size distributions, and to laser diffraction and dynamic light scattering measurements.

Findings: Robust, highly resolutive and concentration-dependent measurement of the PVD and PSD of solid particles and droplets was achieved for diluted to highly concentrated liquid dispersions. As interactions between particles or droplets are dependent on the dispersed phase concentration, accurate characterization of as-formulated industrial liquid dispersions can be performed with SMLS.