In fact, due to the porous nature of the silicone-based coating, paints applied over them are able to penetrate deeply for good adhesion.Properties of Si–C, Si–O, and Si–F bonds In most organosilicon compounds, Si is tetravalent with tetrahedral molecular geometry. The inherent water repellency of silicone resin emulsion paint coatings is overcome by the low surface tension of coatings that are applied over them. This is due to the silicone resin nature of the system, which has much different physical and chemical properties from the elastomeric silicones used in sealants, silicone rubber and other coatings systems. Both laboratory testing and field experience have demonstrated the recoatability of these systems. Often biological growth is mistaken for dirt - in numerous field examples with both silicone primers and paints, the low water absorption and the inherent resistance of silicones to biological attack works to improve façade appearances.Īnother important point about these coatings systems is the ability to paint over them. The coatings resist dirt pickup as water that carries dirt into coatings is repelled. The coatings weather well over time, retaining their color due to the strong bonding between pigment and resin. Other important performance benefits have been observed by examining SREP coated buildings over time. From buildings in northern climates with extreme temperature ranges, including freeze/thaw conditions, to buildings in tropical climates, where heavy rainfall and biological damage from algae and fungus are prevalent, this coating system has provided durable performance over time. This performance has led to wide acceptance in Europe, and more recently in Asia. Even though the latest silicone resin emulsion paint technologies are far superior to earlier technologies, buildings protected with SREP over 30 years ago continue to show excellent durability and appearances. In fact, performance on exterior exposure has been demonstrated to be much greater than that on test fences. This occurs because the emulsifiers in the paint wash out over time, creating a more hydrophobic coating system. Since most damaging effects require water, which can come from a variety of sources in addition to the exterior surface, well-protected façades should be low water absorbing and water vapor permeable.įigure 3/ Durabliity of Silicone Resin Emulsion Paints A-D Demonstrated by Reduction in Capillary Water Absorption The extreme durability of the coating system is shown in Figure 3, where low water absorption actually improves over time on panels placed on a test fence. In addition to protecting exterior construction materials against the effects of water, pollutants and chemical attack, the façade should also be aesthetically pleasing. While many coatings provide sound protection, a relatively new technology exists for improving waterborne architectural paints to increase the durability of coatings for mineral-based building materials.įaçade coatings must fulfill various functions. Coatings are used every day to improve the resistance of building materials to damage from the elements, making the materials last longer and look better. Because these structures readily absorb water, exterior walls can quickly become discolored or damaged. One important characteristic of even the most durable materials is their porous surface structure and hydrophilic nature. Figure 1/ Silicone Resin - Inorganic and Organic Functionality Mineral-based building materials are widely used for their excellent durability.
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