Hydrophobic coating of absorbent surfaces
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Hydrophobic coating of absorbent surfaces

Since today the construction industry is moving towards prolonging the useful life of buildings with its ever-increasing speed, Making building materials resistant, such as concrete, stone, brick, brick facade, etc., against destructive factors such as water and high atmospheric humidity It seems necessary. Most building materials have a lot of porosity and have hydroxyl groups on the surface.

This Groups are water absorbent due to their similarity with water structure and hydrophilicity. Therefore, building materials get wet easily and in Their pores absorb water. Renovation of buildings is one of the important issues in economic planning of countries. In Germany every year About 250 million dollars will be spent to do this. In new buildings, all physical and chemical needs can be met predicted in the planning stage. But there is no such issue for built buildings.

Every building needs specific repairs that depend on the type, nature, materials used and location of the building. This project will investigate the possibility of using organosilane chemistry and produce the appropriate material for covering and protecting the building.

One of the properties of building materials is water absorption, which affects their durability and resistance. Water can be absorbed in both vapor and liquid form.

Vapor absorption occurs mainly through condensation mechanism. To create such a process, the relative humidity of the air must be 100%. Liquid water is absorbed by the holes in the material, which is called capillary absorption or under pressure. But the absorption of liquid water It also happens in lower values ​​of relative humidity. Typically, smaller pores have a greater ability to absorb water.

Among the damages caused to building materials due to the presence of water on the surface and pore structure is weathering.

In chemical degradation materials, moisture as a carrier for aggressive gas compounds such as NO, SO 2, CO 2 or corresponding salts (sulfates, nitrates and carbonates) works. Biological weathering is also caused by the growth of plants or microorganisms inside the rock Water plays an important role in transporting acids and salts as nutrients for microorganisms. Therefore, the protection of the building I It is actually protection against water.

It may be possible to cover them with plastic sheets in order to avoid water ingress in historical buildings that are located in the open space, but this is not practical for tall buildings. It is very important to choose a resistance method that provides long-term protection. The technology that provides long-term protection against water and salt is organosilane chemistry.

Recent advances in science and technology have made it possible to use the latest nanotechnology in the production of environmentally friendly organosilane products for waterproofing various types of building materials. For more than 50 years, organosilane technology has provided a new class of materials with special physical and chemical properties. This research will lead to a new industry based on the cooperation of organic chemistry and silicon.

Organosilane compounds are the only reactive and penetrating materials that provide a long life for structures. Alkyl alkoxy silane (RSiOR’) molecules react with OH groups on mineral surfaces such as glass and stone and form a permanent siloxane bond (Si-O-Si) with the underlying layers. Alkyl groups on the surface change the characteristics of the surface from hydrophilic to hydrophobic.

In order to make a hydrophobic coating, the sol-gel process is widely used in the production of hydrophobic coatings compared to other synthesis methods due to its unique advantages such as performing the process at a low temperature, easy activation of surfaces and high uniformity of the final product.

Therefore, it is expected that a hydrophobic coating will be prepared by the sol-gel method and by using alkyl alkoxy silane as a raw material and surface modifier, by replacing hydrogens with non-hydrolyzable Si-R groups (R = Alkyle) in the hydroxyl groups of the surface.

Alkyl groups on the surface create hydrophobicity.

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