Comment from Flavio Visioli, (9/1/2010, 11:09 AM)

The photacatalytic effect is true,but the durability of the coating it is low (chalkhing problems).Another problems : nano materials are very interesting ,but at the moment are not serious certification on their safety in coatings. Many problems could arrive,the pollutions of these products could be very dangerous.

Comment from Gianluca Guerrini, (9/7/2010, 8:03 AM)

I also have some doubts on this type of photocatalytic building material, in terms of durability. This is due to the (physical) adhesion of the photocatalytic coating on the surface, which can be metallic, glass, concrete or other building material. Indeed, any type of coating is exposed to environmental wheatering and after a certain period tends to disappear. However, there are other photocatalytic materials where the active principle is in bulk, so we can have a prolonged service life. this is the case of cement-based materials which contain titanium dioxide with a chemical-physical bound so that the photocatalyst remains for the guaranteed service life of the manufact. as to the presence of free nanoparticles in the atmosphere, of course this is possible in case of surface coating but not in case of particles inserted in a matrix, like the cement paste. At this moment, photocatalytic cement-based materials (paints, coatings, precast and ready-mix concrete, are the most applied building materials all over in the world, above all in Italy, France, USA, Spain and Germany (more than two millions of square meters). For buildings, the most used products are precast panels and coatings.

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