| Résumé : |
Titanium dioxide (TiO₂) pigment has celebrated over 100 years of commercial manufacture and for most of that time it has been the primary white pigment, providing whiteness, brightness and opacity to paints, coatings, plastics, inks, paper and many other applications.
The terms hiding, hide and opacity tend to be used interchangeably in the coatings industry: hiding power and opacity are defined in the standard way as ‘the ability of a substance or coating to obscure a substrate of contrasting colour’. If a coating contains small particles, light passing through the coating can be internally reflected and diffracted at the interfaces between particles and polymer medium, preventing the light reaching the underlying substrate. This light scattering phenomenon is directly influenced by the refractive index of the different phases through which the light passes. In essence, the larger the difference between the refractive index of the pigment/extender and the continuous phase medium, the greater will be the scattering of light.
Titanium dioxide’s high refractive index, carefully controlled physical properties and relative inertness make it the first choice when light scattering is required, although many see TiO₂ as a ‘necessary evil’ and a costly formulation ingredient.
Where the highest levels of wet opacity are desired, TiO₂ outperforms all other pigments and extenders. |
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Examining the efficiency of titanium dioxide in matt paints and methods of obtaining optimal dry opacity without sacrificing wet hide in SURFACE COATINGS INTERNATIONAL, Vol. 106.5 (09-10/2023)
