These types of paints can solve different problems on different surfaces. Let's know its characteristics, formulation and properties.
by Luis Ernesto Cañas*
Can you imagine a wall that can be cleaned by itself? It may occur with hydrophobic material. Great hydrophobic paint means tiny water droplets do the cleaning for you! If dust or dirt particles accumulate on surfaces coated with super hydrophobic paint, any water splashes, dirt particles are picked up by water droplets due to the micro and nanoscopic architecture of the surface, which minimizes the adhesion of the droplet to that surface.
To understand how this situation happens, we can understand two important points: hydrophobicity and contact angle.
The word hydrophobic comes from the Greek roots hydro, which means water and phobia, that is, to fear or hate. The word hydrophobic describes that a material does not want to interact with water or in water. For example oil. The oil does not mix water, and can be called hydrophobic.
Hydrophobicity is related to molecular polarity. The polarity of the molecules determines the molecules of hydrophobicity or hydrophilicity (protection against air pollution). Molecular polarity depends on the difference in electronegativity between the atoms in a compound and the asymmetry of the compound's structure. The distribution of the charge can be reported, and the shape of the molecules determine the polarity of the molecules. A completely nonpolar bond occurs when the electro negativities are identical and therefore possess a difference of zero. A molecule can be nonpolar, either when there is an equal distribution of electrons between the two atoms of a diatomic molecule or because of the symmetrical arrangement of polar bonds in a more complex molecule.
When we analyze the polarity of the water molecule, we conclude that it is a polar molecule, because water molecules are composed of hydrogen and oxygen atoms and that it carries a partial charge between these atoms. The oxygen in it, as an electronegative atom, attracts electrons from each bond closer to its nucleus, thus creating a more negative charge. Therefore, any charged material, whether negative or positive, will be able to interact with water molecules to dissolve. For example, dissolve salt in water. This is due to the charges of sodium and chlorine ions. If a molecule that does not have a charge, which means that they are not polar. Lacking a charge, these molecules do not have any charge-to-charge interactions that allow them to interact with water. Hydrophobic materials do not dissolve in water, they do not interact with each other.
Another important point is to understand that hydrophobicity is the angle of contact. The contact angle determines the hydrophobicity of the surface. The higher contact angle shows a higher hydrophobicity of a surface. Surfaces with a contact angle <90º are called hydrophilic and those with an angle> 90º as hydrophobic. Some plants of nature such as lotus flowers can reach a contact angle of 170 °, so the contact area of the droplet is only 0.6%. On a hydrophobic surface, dirt particles with an extremely small contact area are collected by water droplets and therefore easily cleaned from the surface.
In the case of porous surfaces, they will penetrate the nanoparticles into the pores by filling them. This will prevent the formation of mold, algae layers, wood parasites (external and internal), and the accumulation of dirt or moisture from the surface.
Within 24 hours after application on smooth surfaces or fabrics or 48 hours in the case of porous and absorbent surfaces, the anti-dirt action is fully developed, consisting of dirt not being able to adhere to the treated surfaces and will come off easily. The treatment does not transform the appearance, perspiration or feel of waterproofed or coated materials.
One hour after application you can step on the layer or transport the objects and store them. When creating eco-paints, two principles are guiding in the formulation. Eco-Paints paint, due to hydrophobicity, dirt particles can not adhere to the surface of the façade and the surface is simply clean of dirt with rain. It protects the wall from bacteria and fungi, ultraviolet resistance makes it more durable and provides the appearance of the first day.
Eco-Paints paint provides long-term cleaning and due to its high dirt collection resistance and hydrophobicity properties, it can be applied on exterior walls of buildings, skyscrapers etc., thus avoiding having to use personnel for cleaning.
* Luis Ernesto Cañas is the manager of Project Advisors for the Chemical Industry. You can be contacted in the e-mail: [email protected]
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