[China Glass Net] Glass mold is an industrial problem in the glass industry. Every spring and summer, due to the high temperature and high humidity weather characteristics, the moldiness of the glass enters the peak period. Therefore, how to make the glass moldproof work has become many glasses. The top priority of the enterprise. Below, I will talk about the main factors of moldy mildew, mildew and glass mold.
First, why is glass moldy?
The glass used in daily life is mostly made of quartz sand (SiO2), soda ash (Na2CO3), limestone (CaCO3) and feldspar, of which SiO2 (about 72%), Na2O (about 15%) and CaO (about 9%), so called soda lime glass, is widely used because of its low cost.
According to research, during the annealing of soda lime glass, alkali ions move to the surface of the glass, making ion exchange easy 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 diffuse from the surface of the glass and gradually diffuse into the glass. When the soluble sodium silicate (Na2SiO3) in the surface layer is hydrolyzed, it is contacted by water. (H2O) Carbonic acid (H2CO3) formed with carbon dioxide (CO2) produces ortho silicic acid (H4SiO4) which is weaker than carbonic acid. If the saturated orthosilicate (H4SiO4) solution is left for a long time, it will be amorphous. Silica (SiO2) precipitates in a milky white color and appears as colloidal particles, precipitates or gels.
Glass mold is generally divided into five stages:
1. At the beginning, water or moisture is adsorbed on the glass surface.
2. Subsequently, water or moisture diffuses into the glass.
3. The soluble silicate in the surface layer is hydrolyzed and destroyed. First, sodium silicate and potassium silicate are hydrolyzed and destroyed. Caustic soda (NaOH) is formed and SiO2 is separated.
4. The separated SiO2 forms a silicone gel which forms a protective film on the surface of the glass 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 surface of the glass to form a soluble salt in the surface film. Due to its strong hygroscopicity, it absorbs moisture and deliquesces, forming a droplet of lye later. As 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 period of time, the gel-like silicone film can be partially dissolved therein, causing severe local erosion of the glass surface to form spots. This is a group of white alkali-rich ions that are formed by the migration of sodium ions from the glass body and reacting with air. A white particle swarm can be observed by scanning electron microscopy.
Second, the phenomenon of glass mold
1. White fog and white spots: mild mildew on the glass surface due to storage time, air humidity or glass quality problems.
2. Rainbow: When the white mist and white spots appear for a long time and are not treated in time, a rainbow will form. At this time, the mildew is still stuck on the glass surface and does not corrode into the glass.
3. Sulfur change: The appearance of glass moldy is the same as mild mildew, but the alkaline moldy component of the glass surface has been corroded into the glass, which is seriously moldy.
4, paper printing: the same as sulfur, moldy outside the glass and inside, is a serious mold.
Moldy identification and inspection methods:
The visual appearance method is a relatively simple and feasible method. The specimen was placed in reflected light and transmitted light to observe the presence or absence of spots and mist on the surface of the glass under concentrated light. These spots and mists cannot be wiped off with cloth or water. The glass in which the above phenomenon occurs indicates that the sample has been moldy. If concentrated glare is observed, a small number of spots and mists are slightly mildewed by the naked eye. If concentrated glare is observed, many spots and light mists are observed by the naked eye. If there is no concentrated beam of light, some spots and fog are observed by the naked eye to be severely moldy.
Moldy can also be observed by spray wetting under natural light.
If there is mildew in the glass, you can seek some mold-free products to solve the problem. For example, Greer (Shenzhen) Glass Technology Co., Ltd. has developed a new type of new mold-free mold product developed by the joint laboratory of Nanjing University and Shanghai Jiaotong University. , the various products of the mold have their own specificity, but also for special customers, personalized after-sales service, provide all-round assistance, you can contact Mr. Cai 13418517322.
Third, mold prevention
On the one hand, it is related to the surface characteristics of the glass itself, and also closely related to the anti-mold treatment measures, the degree of packaging sealing, and the storage and transportation conditions taken before the float glass packaging. When the float glass is formed and annealed, it is generally packaged in-line, and the temperature of the glass is about 50 to 100 ° C. The packaged glass must be in stock and shipped to the user, sometimes for a long time. If you encounter high temperature, high humidity season, improper storage and transportation, moldy glass will appear mold.
Moldy appearance on the air surface of float glass, because the mechanism of the tin surface of the glass itself is defective, the original sheet is packaged and transported during storage, the moldy process at room temperature or slightly above room temperature, the fresh glass surface will The moisture and oil are adsorbed from the surrounding environment, and the form of the OH-group adsorbing water combines with Si4+ to affect the structure of the glass surface. Since OH-ions can form hydrogen chains and adsorb other substances, the cleaned glass surface can be rendered hydrophilic by water, ethanol or sulfuric acid surfaces, but becomes hydrophobic due to the attachment of other substances.
The surface of the glass has the following characteristics: 1 during the annealing process, the alkali ions move to the surface of the glass; 2 the surface is easy to react with O2, SO2, H2O and HCL; 3 the surface strength is low, and the Griffith crack is easy to occur; 4 is easy on the glass surface. Ion exchange; the glassy Sio2 on the surface of 5 can be hydrolyzed to break the Si-O bond; 6 the surface component is easy to evaporate and decompose; 7 the surface is easy to devitrify; 8 the surface has temperature and the like.
Surface defects of glass:
1 There are micropores or voids on the surface of the glass:
It is mainly formed by the volatilization of the surface composition. Due to the volatilization of the alkali, the surface is formed on the surface, and the upper surface of the float glass has more protrusions and depressions than the lower surface (tin surface). The porosity of the glass surface allows the glass to facilitate ion exchange on the surface and allows the surface to easily react with O2, SO2, H2O, HCL, and the like. Therefore, the upper surface of the float glass is prone to mold, and it is easy to perform surface coloring or the like.
2 There are cracks on the glass surface:
These cracks are not mechanical damage, but are related to the internal structure: the surface strength is low and cracks are easily generated.
3 moldy during storage and transportation:
Mildew of silicate glass occurs mainly during storage or transportation after packaging, which is related to packaging, storage and transportation.
The package can be packaged in a hot state or in a cold state with paper or mildewproof powder.
1 is usually stored in a well-ventilated warehouse;
2 Do not allow the glass box to be placed directly on the damp floor in the warehouse;
3 It is not allowed to store glass outdoors and under direct sunlight. Anti-mildew measures against glass: I think it is better to use professional anti-mildew products, such as Gree Glass Technology Co., Ltd., is a professional glass anti-mold industry expert, the business involves the country's major float rolling group company, is anti-mildew The leader of the industry. Nowadays, glass moldproofing and segregation are not only urgent problems for original film companies. In order to extend the anti-mildew time of glass, downstream customers have more guarantees. Many deep-processing enterprises also have this development trend, especially for export products. After a long sea transport, the humidity temperature is quite high, and the glass is very prone to mold. In order to reduce the loss of glass scrap and corporate reputation, the better way is to prevent it, and prepare for mold prevention in advance. Being prepared, the glass companies can stand in the glass industry with higher quality products and higher posture.
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