July 23, 2015

Pigments, Coatings, & Adhesives

In product development, formulators seek to optimize coating characteristics such as flow behavior film thickness, uniformity, opacity and storage stability. The Acorn Area and the Acorn Drop measurements provide the pigments and coatings industry with a valuable tool to enhance product performance in development, and later, during manufacturing, to monitor product quality.

TiO2-Fluoresein

Formulation Development

The smallest particles have the biggest influence on flow behavior. Light based particle size measurements have difficulty detecting small particles among large ones, especially at higher concentrations. Particle wetted surface area measurements like those from the Acorn Area are very sensitive to the smallest particles and don’t assume that the particles are spherical, hence they provide a much more precise tool to study flow behavior.

Reducing the particle size or decreasing the particle size distribution (e.g. by milling) will significantly increase the available surface area. This dramatically affects not just adsorption onto the particle surface but also the interaction between particles and system properties such as suspension stability, rheology and adhesion, all of which directly impact the ability to obtain a uniform coating. Competitive adsorption and/or displacement of polyelectrolytes, macromolecules and surfactants at interfaces can be monitored using the Acorn Area. It is straightforward, especially using the flow-through option of the Acorn Area, to determine “optimum coverage” of an adsorbed component for the best storage stability.

Despite the importance of the particle surface-liquid interface on product performance, until the Acorn Area, no particle analyzing technology was available to determine the wetted surface area of suspensions and slurries. The particle analyzers using gas adsorption (BET/N2) require that the particles first be separated from the suspending liquid and dried and degassed, a tedious process which often produces misleading results. Surface area measurement on a dry powder can yield values that are not relevant to the material in the (wetted) dispersed state.

paint-splash coatingStability

Changes in the particle-liquid interface can be detected with the Acorn Area. Coating formulations can be measured non-invasively, without further preparation. The same aliquot of sample can be monitored over days, weeks or months. The effects of temperature can also be studied using one of the Acorn Area temperature control options.

The Acorn Drop measures droplet size and distribution for emulsions without dilution. Drop size measurements using light based techniques involve significant dilution, influencing the delicate balance of the emulsion formulation. The Acorn Drop measurements are also non-invasive, enabling similar advantages to the Acorn Area, but for emulsions.

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