Hindered amine light stabilizers in pigmented coatings

It is common practice to combine hindered amine light stabilizers (HALS) with UV absorbers (UVA) for optimal protection of coatings and plastics. The ratio of UVA and HALS strongly depends on the concentration of pigments (acting as UVA) used in the paint; that is, a clearcoatings require higher amounts of UVA, whereas opaque pigmented coatings require higher amounts of HALS. Here, especially basic HALS types can interfere with paint components like, for example, pigments due to acid/base interactions. In this article, we want to discuss the influence of HALS basicity on long-term performance in opaque white pigmented solventborne (SB) and waterborne (WB) coatings for industrial applications in correlation to the quality of the used TiO2.