Waterborne modified-silica/acrylates hybrid nanocomposites as surface protective coatings for stone monuments

The weathering and deterioration of historical buildings, as well as that of many monuments or sculptures using natural stones, is a problem that has been known since antiquity. In this work, we have obtained an innovative waterborne coating made of silica-armored polymer particles. The synthetic approach aimed at maximizing the presence of the silica at the particle surface and its attachment to the polymer is discussed. The performance of the coating is evaluated in two natural building stones that have widely different porosities, Carrara marble and Lecce stone. It was found that the coatings maintained the aesthetics upon ageing, reduced liquid water absorption by capillary and let the water vapor permeate. Moreover, the addition of the nanosilica improves the mechanical resistance, making them suitable to use as protective coatings in total agreement with the regulations in the field of protective natural stones.