Views: 0 Author: silk screen glass Publish Time: 2021-07-02 Origin: Site
Moldy glass is an occupational problem for the glass industry. In the spring and summer of each year, due to the high temperature and humidity climate, the moldy of glass enters the peak period. Therefore, how to prevent mildew of glass has become the first task of many glass companies. . Next, automotive glass manufacturers talk about the primary factors of glass moldy, moldy scenes, and methods for glass mold prevention.
1. Why is the glass moldy?
The glass used in daily life is mostly made of quartz sand (SiO2), soda ash (Na2CO3), limestone (CaCO3), and feldspar as the primary raw materials, among which SiO2 (content 72%), Na2O (content 15%) and CaO (9% content), so called soda lime glass, is widely used because of its low cost.
According to research, during the annealing process of soda lime glass, alkali ions will move to the surface of the glass, making it easy to perform ion exchange on the surface of the glass; for example, the glassy Sio2 on the surface can be hydrolyzed.
Therefore, when the soda lime glass is stored in a humid environment, water or moisture will be adsorbed on the surface of the glass and gradually dispersed into the glass. When the soluble sodium silicate (Na2SiO3) in the outer surface layer is hydrolyzed, it will be touched by the water. Carbonic acid (H2CO3) composed of (H2O) and carbon dioxide (CO2) will produce orthosilicic acid (H4SiO4), which is weaker than carbonic acid. Assuming a full orthosilicic acid (H4SiO4) solution is left for a long time, there will be amorphous The silicon dioxide (SiO2) deposits, the color is milky white, and appears as colloidal particles, sediments or gels.
Moldy glass is generally divided into five periods:
1. Initially, water or moisture is adsorbed on the surface of the glass.
2. Subsequently, water or moisture disperses into the glass.
3. The soluble silicate in the outer surface layer is hydrolyzed and damaged. The first is that sodium silicate and potassium silicate are hydrolyzed and damaged. The formed caustic soda (NaOH) does not separate from SiO2.
4. The separated SiO2 generates silica gel, which forms a protective film on the surface of the glass, which prevents further corrosion effects.
5. The caustic soda formed by the hydrolysis reacts with the carbon dioxide in the air to produce sodium carbonate, which gathers on the surface of the glass to form the soluble salt in the outer film. Because of its strong hygroscopicity, it absorbs water and deliquescence, eventually forming lye droplets. When the surrounding temperature and humidity change, the concentration of these droplets also changes. Assuming that when the concentrated lye droplets and the glass are touched for a long time, the gel-like silica film can be partially dissolved between them, causing severe partial corrosion on the glass surface, forming mottle. This is the white alkali-rich ion cluster generated by the removal of sodium ions from the glass body and reacting with the air. Scanning electron microscopy can investigate the white particle group.
Second, the sight of moldy glass
1. White fog and white spots: the slightest mildew on the surface of the glass due to storage time, air humidity or glass quality questions.
2. Rainbow: When the white fog and white spots are not treated in time for a long time, it will form a rainbow. At this time, the moldy condition only stays on the surface of the glass and does not corrode into the glass.
3. Sulfur change: The appearance of moldy glass is the same as that of mild moldy, but the alkaline moldy components on the surface of the glass have now corroded into the glass, which is attributed to severe moldy.
4. Paper printing: Same as sulfur change, moldy on the outside and inside of the glass, which is severe moldy.