Titanium dioxide often serves as interference layer in pearles-cent pigments, but exhibits photocatalytic activity. While this can be determined by a number of methods, they are all time-consuming. The "Brilliant Blue FCF" method presented here is fast and yields results which correlate with Florida weathering while requiring less effort and only small amounts of pigment. Pearlescent pigments are universally employed in all kinds of paints and coatings and allow a wide range of colours and effects to be achieved. For outdoor applications and especially for use in automotive coatings, these pigments have to meet very stringent requirements on weatherability. The majority of pearlescent pigments consists of a transparent substrate, such as mica, glass, silicon dioxide or aluminium oxide, which is coated with one metal oxide layer or a sequence of different metal oxide layers of different refractive index. Pigments structured in this way exhibit colour interference [1]. Due to its high refractive index of 2.55 to 2.71 [2], titanium dioxide often serves as interference layer in pearlescent pigments. However, titanium dioxide puts the long-term durability of coatings at risk, because its rutile modification also exhibits high photocatalytic activity (Figure 1), which can accelerate the oxidation of organic polymers [3].
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