Enhancing TiO2 dispersion performance
How to enhance TiO2 dispersion
TiO2's theoretical optimum particle size is between 0.2 and 0.3 microns, but as received is considerably larger mainly because of the formation of agglomerates in handling during the manufacturing process.
The energy of simply stirring pigment into water or binder is not great enough to overcome the particle attractive forces preventing the breakup of the agglomerates. The presence of these agglomerates adversely affects the hiding power, tinting strength and other end-use properties of the coating.
The graph below illustrates the effect of TiO2's dispersion states vs. particle size distribution on pigment properties:
Figure 1: TiO2 Dispersion States vs. Particle Size Distribution
The process of breaking down agglomerates, otherwise known as dispersion, occurs in 3 steps:
- Wetting - air and other substances are displaced from the pigment surface by solvent, dispersant / surfactant and binder
- Grinding - agglomerates of pigment particles are broken and separated into an optimum particle distribution
- Stabilization - separated particles are maintained by either charge or steric stabilization
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