The self-cleaning effect of photocatalytic architectural paints
The efficiency of waterborne paints containing photocatalytic titanium dioxide to reduce the dirt-pickup, outdoors, was investigated. Under climatic conditions (UV-radiation, water and oxygen) photocatalytic titanium dioxide induces the oxidation of organic material and by developing an extremely hydrophilic paint surface, causes the cleaning of organic and inorganic particles during rainfall. Through photocatalysis, the organic binders can be decomposed, too. The disintegration of the organic binder in the paint becomes apparent as the process of "chalking". Therefore, the binders used in the formulations of the paints included organic types (styrene acrylate) and inorganic types (silicones and silicates) in different mixtures. Conventional paints in comparison with photocatalytic paints were exposed two years to different outside conditions. It was found, that the lower dirt-pickup of the photocatalytic paints was caused mainly by the stronger "chalking" of the paints containing parts of organic binders.