"Easy-clean glass", which is also vividly called "self-clean glass" or "Auto-clean glass" in business. 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 water-containing and even oil-containing liquids) to adhere to the surface of the glass or can be easily washed away by water (or rainwater). In this way, the surface of the glass is very easy to keep clean, reducing the trouble of cleaning the surface of the glass and also saving the increasingly scarce water resources.
This special type of coating is known as "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 is a type of glass with a surface that has high hydrophobicity similar to the lotus effect, preventing water from fully adhering to the glass. This causes the surface tension of water droplets to form a teardrop-like shape, allowing the water droplets to naturally slide off and carry away dust, thus giving the glass an easy-to-clean effect. Dust cannot accumulate, and over time, the effect is significantly different from the water stains that accumulate on ordinary glass.
Basic characteristics
The phenomena of two basic physical characteristics are opposite, namely:
A. Hydrophobicity (also known as "hydrophobicity", English :Hydrophobe): It refers to the strong repulsive effect of a substance's molecules on water. When water is on the surface of a hydrophobic object, it forms a large contact Angle and turns into a droplet shape. The lotus leaves we often see have this effect.
B. Hydrophilicity (English :Hydrophile): It refers to the ability of molecules to form transient bonds with water molecules through hydrogen bonds, making it particularly easy for water to combine with hydrophilic surfaces. The capillary phenomenon we often see is based on this principle.
Glass section view. Glass section view
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 type: Its main component is silicone (or silicone organic resin) or other oily materials. When applied to the surface of the material, it gives a smooth and oily feeling. However, it does not react with the silica molecules on the surface of the material to form a strong nano-film. Instead, it merely fills in the uneven surface of the material that is invisible to the naked eye, making the surface of the material smooth and uniform Its advantage is that it has a strong repulsive effect on water (but not oil), but its disadvantage is poor adhesion. Within a relatively short period of time (6 to 12 months), its property of repulsive water will be significantly reduced.
The second category: The main component is titanium dioxide (TiO2). After coating a layer of titanium dioxide film on glass, titanium dioxide has superhydrophilicity due to its excellent photocatalytic properties under the action of (ultraviolet) light energy. By taking advantage of this super-hydrophilic property (contrary to the hydrophobic property of the Golden Seal coating), it enables very small water droplets to coalescing into large ones, which then fall off under the force of gravity. As a result, the stains adhering to it can be easily washed away by water, giving the glass an easy-to-clean characteristic. Therefore, it is particularly suitable for outdoor architectural glass. Its advantage is that it is cheap, but its disadvantages are 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-proof performance. 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 self-clean and does not fog up. The surface of this type of glass has "dual wettability", allowing it to simultaneously absorb both water and oil. Therefore, when there is water vapor on the glass, it will spread throughout the entire surface without condensing into water droplets. Furthermore, water can seep into oily dirt through such mutual accommodation and wash away the oil stains, thus having a strong self-cleaning ability. Someone has conducted such an experiment: when water vapor is sprayed onto glass, ordinary glass is already covered with fog droplets, but this kind of glass can still be read through words 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 very easy to get dirty. In addition, 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 slide off. During the drying process of the water droplets, they are very likely to adsorb dust in the air, and after drying, water marks are formed. Over time, dirt forms.
Self-cleaning glass, also known as self-cleaning glass, is an eco-friendly "green glass". It can be made by coating a layer of transparent titanium dioxide and photocatalyst film on the surface of flat glass. When the titanium dioxide photocatalyst film, known as a photocatalyst, is exposed to sunlight, fluorescent lamps or ultraviolet rays, under the excitation of external light, the organic matter and pollutants adhering to the surface will be transformed into carbon dioxide and water and automatically eliminated.
