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Measurement of electrostatic stability of various TiO2 dispersions

Introduction
Titanium dioxide can be utilized in various applications such as pigment base in paints, coatings, plastics and laminates. During both, the production process at the TiO2 producer and the manufacturing process of paints, coatings and composite materials, avoiding the coagulation and agglomeration of the TiO2 dispersion is important.
Surface chemistry of the TiO2 dispersion can be controlled during the measurement of Electrokinetic Sonic Amplitude (ESA) by regulating the pH value e.g. for avoiding flocculation of dispersion. This means: the zeta potential of the dispersion should not be or close to zero.
Zeta potential is a dimension of the effective surface charge of particles and the interaction between the particles with ions in solution and particles among each other. Characterising the absolute surface charge (in an aqueous dispersion) of the TiO2-pigment, negative or positive in the unit [mV], gives a decisive parameter for an ultimate application of the product.
The zeta potential depends on the kind of solvent, the nature and amount of the ions in solution (specific conductivity), and the pH value. It is also the main factor determining the stability of the whole dispersion.

Results and discussion
Measuring the Electrokinetic Sonic Amplitude ESA delivers a clear distinction of the electrostatic properties of various grades of TiO2 in aqueous dispersions.
The measurement results in Figure 1 show that the different TiO2 grades differ in isoelectric point IEP and with regard to their zeta potential significantly from each other.
Handling TiO2 dispersions in a range beyond the IEP avoids any kind of flocculation. Choosing pH values in an extreme area could be a disadvantage regarding both, the electrostatic property of the pigment surface and the ionic charge in the dispersion.

 

Conclusion
Electrokinetic Sonic Amplitude (ESA) measurements of highly concentrated dispersions are standard measurement methods. The ESA technique is state of the art for electro acoustic methods and has been developed for a whole range of different applications. During the technical process dispersions are often found to be highly concentrated, muddy, coloured, tempered, or electro-statically affected by additive formulations. Sedimentation is often inhibited by powerful agitators in the large scale treatment containers. All these process conditions mentioned before can be involved in the stability analysis via ESA. The results of the analysed highly concentrated samples correlate directly with the electro kinetic properties of the dispersed particle in both, the raw material and the final product.

 

By using test equpiment on left hand side we carry out dispersion research and give answer to important questions:

 

How dispersions are stabilized and how is the influence on the dispersion properties ?

In wich way process can affected by parameter of formulation.

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