Glass mold is an industrial problem in the glass industry. Every spring and summer, due to the high temperature and high humidity weather, the glass mold enters a peak period. Therefore, how to do a good job of preventing glass mold has become the primary task of many glass companies.
Why Does the Glass Get Moldy？ We Need to Talk About the Composition of the Glass
The glass used in daily life is mostly made of quartz sand (SiO2), soda ash (Na2CO3), limestone (CaCO3), and feldspar, among which SiO2 (about 72%), Na2O (about 15%), and CaO (content about 9%), so-called soda-lime glass, is widely used due to its low cost. According to research, during the annealing process of soda-lime glass, alkali ions will move to the glass surface, making ion-exchange easy on the glass surface; for example, the glassy Sio2 on the surface can be hydrolyzed. Therefore, when soda-lime glass is stored in a humid environment, water or moisture will be adsorbed on the glass surface and gradually diffuse into the glass. Carbonic acid (H2CO3) formed by (H2O) and carbon dioxide (CO2) will produce orthosilicic acid (H4SiO4) that is weaker than carbonic acid. If the saturated orthosilicic acid (H4SiO4) solution is placed for a long time, there will be amorphous Silica (SiO2) precipitates, milky white in color, and appears as colloidal particles, precipitates or gels.
Glass Mold is Generally Divided Into Five Stages
1. Initially, water or moisture is adsorbed on the glass surface.
2. Subsequently, water or moisture diffuses into the glass.
3. The soluble silicates in the surface layer are hydrolyzed and destroyed. The first is that sodium silicate and potassium silicate are hydrolyzed and destroyed. Caustic soda (NaOH) is formed and SiO2 is separated.
4. The separated SiO2 forms a silica gel, which forms a protective film on the glass surface, which prevents further erosion.
5. The caustic soda formed by hydrolysis reacts with carbon dioxide in the air to form sodium carbonate, which accumulates on the glass surface to form soluble salts in the surface film. Due to its strong hygroscopicity, it absorbs water and deliquesces, and finally forms small droplets of lye. When the surrounding temperature and humidity change, the concentration of these droplets also changes. If the concentrated lye droplets are in contact with the glass for a long time, the gelatinous silicon oxide film can be partially dissolved in it, and the glass surface will undergo severe local erosion and form spots. This is a white alkali-rich ion group formed by the migration of sodium ions from the glass body and the reaction with air. A scanning electron microscope can observe white particles.
