TY - JOUR

T1 - Dispersion state of TiO2 pigment particles studied by ultra-small-angle X-ray scattering revealing dependence on dispersant but limited change during drying of paint coating

AU - Lof, David

AU - Hamieau, Guillaume

AU - Zalich, Michael

AU - Ducher, Pascal

AU - Kynde, Soren

AU - Midtgaard, Soren R.

AU - Parasida, Claire F.

AU - Arleth, Lise

AU - Jensen, Grethe

PY - 2020/5/1

Y1 - 2020/5/1

N2 - The dispersion state of titania (TiO2) 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. By having the particles well-dispersed, with limited aggregation, the best opacity can be obtained with the smallest amount of pigment. The aggregation of titania particles is typically investigated using various microscopy techniques on the dry coating. In this work, Small-Angle X-ray Scattering was applied as a non-invasive tool to probe the distribution of titania during the coating drying process. The titania pigment particles were dispersed by using either a polymeric surfactant or nanosized silica particles as dispersant. The use of silica nanoparticles resulted in the highest degree of dispersion, both in dilute suspension, and in acrylic and alkyd-based coating formulations. Only minor changes in the aggregate structure was observed during drying of the coatings, indicating that the optical performance is to a large extent determined already before drying, in the wet paint. For the formulations containing nanosilica dispersant, the drying time was increased by diluting the paint or by adding less dryer catalyst. The former resulted in a reduced pigment dispersion, whereas the latter seems to increase the degree of dispersion. In both cases, however, the change of dispersion during the drying phase remained minor.

AB - The dispersion state of titania (TiO2) 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. By having the particles well-dispersed, with limited aggregation, the best opacity can be obtained with the smallest amount of pigment. The aggregation of titania particles is typically investigated using various microscopy techniques on the dry coating. In this work, Small-Angle X-ray Scattering was applied as a non-invasive tool to probe the distribution of titania during the coating drying process. The titania pigment particles were dispersed by using either a polymeric surfactant or nanosized silica particles as dispersant. The use of silica nanoparticles resulted in the highest degree of dispersion, both in dilute suspension, and in acrylic and alkyd-based coating formulations. Only minor changes in the aggregate structure was observed during drying of the coatings, indicating that the optical performance is to a large extent determined already before drying, in the wet paint. For the formulations containing nanosilica dispersant, the drying time was increased by diluting the paint or by adding less dryer catalyst. The former resulted in a reduced pigment dispersion, whereas the latter seems to increase the degree of dispersion. In both cases, however, the change of dispersion during the drying phase remained minor.

KW - Pigment particles

KW - Drying paint coating

KW - Colloidal dispersion

KW - Coating formulation

KW - Small-angle x-ray scattering

KW - FILM FORMATION

U2 - 10.1016/j.porgcoat.2020.105590

DO - 10.1016/j.porgcoat.2020.105590

M3 - Journal article

VL - 142

JO - Progress in Organic Coatings

JF - Progress in Organic Coatings

SN - 0033-0655

M1 - 105590

ER -