Pearlescent Pigments: history, properties and application in powder coatings

Special effect pigments are gaining more and more attention from industries because they allow obtaining peculiar optical effects, which can be exploited in many applications, from plastics and car coatings to the cosmetic field. Among the special effect pigments, it is possible to count metal effect pigments and pearlescent pigments. The latter type shows great potentiality as these pigments are easily produced with controlled morphological characteristics, thus having unique optical properties, such as dependence of colour on the viewing angle, colour change effects and crystal-like effects. There are many types of pearlescent pigments available on the market: the most important part is represented by mica-based pigments, but also pigments based on silica or alumina flakes are becoming increasingly popular. Alumina-based pigments show the well-known advantages of micabased pigments together with the ease of incorporation in many different binders as well as peculiar optical effects. In the last decades, researchers focused their attention on the development of new pearlescent pigments; but in recent years emerged the necessity to study the behaviour of these pigments within commercial polymer binders as well. The study of the pigment-matrix system is fundamental to gain further insights on the behaviour of the single components and on their combined effects. For this reason, it is possible to assess the protection and aesthetical properties of the coatings admixed with pearlescent pigments exploiting UV exposure tests as well as salt spray exposure tests.