Analysis of powder and dispersion. Development of formulations and pigment testing
dispersions
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ESA stability analysis for quality control, product and process development
The measurement of suspensions, dispersions, colloidal and pasty formulations, from low to high concentrations. Simultaneous measurement of zeta potential, pH, specific conductivity and temperature is possible during vigorous stirring. The ESA technology enables work in the areas of dispersion research and formulation development. In particular, by simultaneous measurement during the titration of different species that interact with the particle surface.
Measuring principle of the ESA technology
The ESA method for characterizing the charge stability of particles in a dispersion is an electroacoustic measurement technique.
An oscillating voltage is applied to a suspension, dispersion or emulsion generated by an AC power source. Charged particles in the dispersion vibrate at the frequency of the externally applied electric field. One or more frequencies can be created. The oscillation of the particles at these frequencies creates sound waves. The amplitudes of these sound waves are measured as Electrokinetic Sound Amplitude (ESA). This ESA signal is proportional to the dynamic mobility of the particles and this in turn to the zeta potential of the particles present in the dispersion. A prerequisite for using this effect is a certain density difference between the dispersion medium and the particle. To generate signals that can be evaluated, this density difference must be at least 0.1 g/cm3.
The ESA technology, as the most modern of the electro-acoustic methods, is specialbeen worked out in a different way for different applications.Dispersions in technical production processes are often highly concentrated, cloudy, color-tempered or electrostatically influenced by added additive formulations. Sedimentation processes are often prevented in the process by powerful agitators in large treatment vessels. All of these process states mentioned can be included in the stability analysis using electrokinetic sound amplitude ESA. The data from the samples analyzed in the highly concentrated form relates directly to the electrokinetic properties of the particulates in the raw material or in the finished product.
We conduct dispersion research and provide answers to important questions:
How are dispersions stabilized and what effects does this have on the properties?
How can processes be influenced by formulation parameters?
Measurement of Electrostatic Stability
highly concentrated TiO2 pigment
Dispersions using ESA
ESA analysis for quality control, product and process development
With the electrokinetic sound amplitude ESA measurement method, the surface chemistry of the dispersion can be controlled by adjusting the pH value. The dispersion should be handled in a pH range in which it does not flocculate. This means: The zeta potential of the dispersion must not have a value equal to zero or close to zero.
The zeta potential of the dispersion is a measure of the effective surface charge and the interaction of the particles with each other. The characterization of the absolute surface charge of the particles in the aqueous dispersion (negative or positive in the unit [mV]) is a crucial parameter for the final application of the product.
The zeta potential depends on the type of solvent, types and amount of ions present in the dispersion (specific conductivity), pH value. In particular, the zeta potential is a measure of the electrostatic stability of the entire dispersion.
