"Easy-clean glass" is often vividly referred to in business as "self-clean glass (or Auto-clean glass)". It generally refers to the application of a special coating on the surface of glass, which makes it difficult for dust or dirty liquids (including those containing water or even oil) to adhere to the surface of the glass, or makes it relatively easy to be washed away by water (or rain). In this way, the surface of the glass is very easy to keep clean, reducing the trouble of cleaning the glass surface and also saving the increasingly scarce water resources.
This special kind of coating is what is called "easy-to-clean coating" or "self-cleaning coating". It was developed by taking advantage of two fundamental physical characteristics that objects possess in nature. So-called easy-to-clean glass refers to the glass surface having a high hydrophobicity similar to the lotus effect, which prevents water from being completely adhered to the glass. The surface tension of the water droplets themselves creates a teardrop-like phenomenon. The water droplets will naturally slide off and carry away dust, giving the glass an easy-to-clean effect. Dust will also be unable to accumulate. Compared with the water stain accumulation of ordinary glass, the effect over a long period of time is quite obvious.
The phenomena of the two basic physical characteristics are manifested in opposite directions, namely:
A. Hydrophobicity (also known as "hydrophobicity", English: Hydrophobe) : It refers to a substance (molecule) having a strong repulsive effect on water. When water is on the surface of a hydrophobic object, it forms a large contact Angle and appears as water droplets. The lotus leaves we commonly see have this effect.
B. Hydrophilicity (English: Hydrophile) : It refers to the ability of molecules to form short-term bonds with water molecules through hydrogen bonds, making it particularly easy for water to combine with hydrophilic surfaces. The capillary phenomenon we commonly see is based on this principle.
The "easy-to-clean coatings" or "self-cleaning coatings" available on the market for glass and ceramic surfaces can roughly be classified into three categories:
The first category: The main component is silicone (or silicone organic resin) or other oily materials. When applied to the material surface, it gives a smooth and oily feeling. However, it does not react with the silica molecules on the material surface to form a strong nano-film. Instead, it merely fills the uneven material surface that is invisible to the naked eye, making the material surface smooth and uniform. Its advantage is that it has a strong repulsive effect on water (but not on oil), but its disadvantage is poor adhesion. Within a relatively short period of time (6 to 12 months), its water-repelling property will be significantly reduced.
The second category: The main component is titanium dioxide (TiO2). After coating a layer of titanium dioxide film on the glass, titanium dioxide has superhydrophilicity due to its excellent photocatalytic properties under the action of (ultraviolet) light energy. By taking advantage of this superhydrophilic property (contrary to the hydrophobic property of Golden Seal paint), it causes very small water droplets to coalesced into large ones and fall off under the effect of gravity, thus allowing the stains adhering to them to be easily washed away by water, making the glass easy to clean. Therefore, it is particularly suitable for outdoor architectural glass. Its advantage is that it is cheap, but the disadvantage is that it must be exposed to ultraviolet light and its adhesion is also poor.
The third category: Its main component is inorganic nano-silicon material. It is characterized by a super hydrophilic coating on the surface and good dust prevention. It does not rely on sunlight exposure and still functions in a completely dark environment. It is an upgraded version of titanium dioxide type products.
A Japanese chemist invented a kind of glass that can clean itself and does not fog up. The surface of this kind of glass has "dual wettability", allowing it to come into contact with both water and oil at the same time. Therefore, when there is water vapor on the glass, it will spread throughout the entire surface of the glass instead of condensing into water droplets. In addition, water can seep into oily dirt through such mutual understanding and accommodation, washing away the oil stains and thus possessing a strong self-cleaning ability. Someone has conducted such an experiment. When water vapor is sprayed onto the glass, ordinary glass is already covered with mist droplets, while this kind of glass can still be read by people through text and pictures.
The surface of ordinary glass is prone to static electricity, which can absorb floating dust in the air and vehicle exhaust. Over time, it is extremely easy to get dirty. Additionally, when it rains, the contact Angle between the glass and water is 30 to 40 degrees, so water droplets are easily formed on the glass surface and are not easy to slip off. During the drying process of the water droplets, they are also very likely to adsorb dust in the air. After drying, water marks are formed. Over time, dirt forms.
Self-cleaning glass, also known as self-purifying glass, is an eco-friendly "green glass". By coating a layer of transparent titanium dioxide and photocatalyst film on the surface of flat glass, self-cleaning glass can be made. When the titanium dioxide photocatalyst film, known as photocatalyst, is exposed to sunlight or fluorescent lamps and ultraviolet rays, under the excitation of external light, the organic matter and pollutants adhering to the surface will be converted into carbon dioxide and water and automatically eliminated
