SILICONES AS SEALERS FOR MASONRY COATINGS

Silicones ore highly suitable as sealers for masonry coatings. The dev elopment of water-thinnable, solvent-free emulsions makes the use of t raditional solvent-based products obsolescent. Water absorption con be reduced considerably and the risk of damage to the coating, by the fo rmation of crocks or deposits of salts in the substrate, is reduced us ing nine different sealers and two film-forming emulsion points, it wa s demonstrated that the adhesion of these coating systems to silicone- based sealers is not usually adversely affected. In contrast, it was f ound that in the case of a microporous coating with low binding forces in the system, the test method used does not always yield a clear ass essment of the adhesion properties. It was recognised that with carefu l selection of the sealers, the risk, with regard to the deterioration of adhesion can also be avoided. Highly dilute silicone emulsions wit h the hydrophobic properties have no influence on the adhesion. Mixtur es with polymeric hinders even yield improved adhesion properties.