Silicon organic water repellent

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Silicone hydrophobic powder (SHP), is a versatile chemical additive known for its remarkable water-repellent properties. It is a fine, white powder composed of silicone polymer, a synthetic polymer known for its unique combination of flexibility, stability, and resistance to various environmental factors.[1]

Commercially available siliconates include potassium methyl siliconate (CAS 31795-24-1, CH5KO3Si) and sodium methyl siliconate (CAS 16589-43-8, CH5NaO3Si). These are supplied as a concentrate in water with an active content of between 30% and 40% by weight. This solution is further diluted in water prior to their application by spraying, dipping or rolling to a mineral building material, such as brickwork, to make the surface water-repellent.[2] The dilution is clear and stable with a high pH of 13 to 14. When applied to a surface, the siliconate reacts with carbon dioxide in the air to form an insoluble water-resistant treatment within 24 hours.

CH5KO3Si + silanol functional substrate OHSi → CH4O3Si + KOH

The methyl group has now attached itself to the substrata.

2KOH + CO2 → K2CO3 + H2O

The salts formed by this reaction are often the cause of white efflorescence when too much of the solution is applied to the surface.

Types and applications

References

See also

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