Dispersion state of TiO2 pigment particles in wet coating formulation and during drying studied by X-ray scattering

 
Good dispersion of pigment particles in coatings is crucial to obtain optimal optical properties while minimizing the consumption of pigment, and thereby the cost and environmental impact of the product. The distribution of pigment is typically investigated using various microscopy techniques on the dry coating. In this recently published work, Small-Angle X-ray Scattering was applied as a non-invasive tool to probe the distribution of titania in wet formulation and during the drying process. The results provide information about the local density around the pigment particles, and the size and density of the larger clusters that they form. The particles were dispersed using either a polymeric surfactant or nanosized silica particles as dispersant with the latter resulting in the highest degree of dispersion in both acrylic and alkyd-based coating formulations. Only minor changes were observed during drying, indicating that this process is not decisive for the optical performance.