*2.3.2. Rheology*

An ink with required rheological properties can be successfully applied to the image on a plate, transferred correctly to the stock and finally, retain its form as a print. Each printing technique has specific requirements. For opacity, it is important to select pigment and pigment volume concentrations that play a role on opacity, gloss and whiteness, but also on the rheology of the ink. Different pigment grades have different medium absorption. As a consequence, the rheology of the ink at the time of application will be affected. Many ingredients, apart from TiO<sup>2</sup> pigments, will affect the final rheology of the ink. It is important to note that formulation of inks calls for much practical experience and skill.

controlled conditions (*T*, pH, precursor dosing rate). Under such conditions, the alumina surface-treated particles are separated from each other; coating is uniform and dense, covering the entire surface of the particle (**Figure 19**). Such particles exhibit excellent optical properties, as demonstrated in **Table 3**. In the case where the process of surface treatment started from suspension with more dispersed or deagglomerated particles (intense milling), higher

**Sample Gloss Scattering** Poorly milled material 24.4 97.4 More intense milling 40.5 104.1

A layer of alumina oxide layer can increase the amount of ─OH groups on the particle surface, which can improve the dispersibility of the particles and provide more active sites for further

surface-treated under controlled conditions exhibit significantly higher light scattering efficiency

particles with incomplete coatings, produced under uncontrolled conditions (**Figure 20**).

For printing inks production approximately 10% more solvent was needed. Since the viscosity

organic modification; this was evidenced from the results obtained by OD method. TiO<sup>2</sup>

.

particles

437

surface. Lower LSE was determined for

particles with incomplete coatings was highly viscous.

TiO2 Applications as a Function of Controlled Surface Treatment

http://dx.doi.org/10.5772/intechopen.72945

with complete and incomplete coatings.

gloss was obtained for the system with incorporated TiO<sup>2</sup>

**Table 3.** Influence of milling and coating process on optical properties.

due to complete aluminum layer coating the entire TiO<sup>2</sup>

**Figure 20.** Light scattering efficiency (LSE) for pigmentary TiO<sup>2</sup>

Printing ink with incorporated TiO<sup>2</sup>

*2.3.4. Optical density*

TiO<sup>2</sup>

It is vital to incorporate TiO<sup>2</sup> pigment into the printing ink medium in a way that maximum dispersion is achieved. In the case of a poor dispersion stability even viscosity could be affected.
