Masonry water repellants silicone resins

The clear-colorless nature of silicone repellents allows preservation of the original appearance of the concrete. Their lack of film formation leaves the masonry pores open, thereby allowing transport of moisture outward to the atmosphere. They are highly durable to environmental conditions and will retain their repellent properties for several years. There are two types of water-repellent silicones (1) one is the resin-solvent type that is characterized as a partially hydrolyzed, partially alcoholized silicone resin dissolved in a hydrocarbon solvent. Generally, such products approach the 5% nonvolatile level. (2) The second is a water-soluble alkaline silicone repellent that is recommended for use on limestone and other nonsiliceous stone and masonry. 

A substance that, because of its physicochemical nature, will not mix or blend with another substance.. All hydrophobic materials have water-repellent properties due largely to differences in surface tension or electric charges, e.g., oils, fats, waxes, and certain types of plastics. Silicone resin coatings can keep water from penetrating masonry by lining the pores, not by filling them they will not exclude water under pressure. 

Ethyl silicate (tetraethoxysilane) is often used without modification as a water-repellent material for concrete and masonry in general. All, or nearly all. the ethoxyl groups are hydrolyzed by the moisture of the air to form cross-linked watcr-rcpcllcnt polymers. The material is applied in desirable thickness, dissolved in some volatile solvent which soon evaporates. Silicone resins which arc partially condensed before application, or even fully condensed, can also be used here. In the latter case, hardness is achieved on evaporation of the solvent. Certain silicone resins arc useful as hydrophobic agents for the impregnation of paper and fabrics. 

Building materials exposed to weathering are corroded by the action of atmospheric influences, especially water destruction is unavoidable in the long term. Water-repellent treatments can certainly not totally stop these harmful processes, but, given adequate envelopment and attachment to the substrate, nanoscale silicone resin networks can retard material decomposition because of their high durability. Since damage caused by hydrophobic measures can be virtually ruled out if the treatments are properly applied, the organosilicon compounds used in masonry protection will become more and more widely used. 

The single largest use of silicone resins is as water repellents for stone and masonry. The resins also find important applications in paints and finishes, especially for high-temperature use, and increasingly as additives to conventional paints. Among the numerous speciality uses which have also been developed, siloxane resins are used to coat pharmaceutical pills and as encapsulants for electronic components. 

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