When exchanging glass knowledge with the masters of the door and window factory, many people found that they had fallen into a mistake: the insulating glass was filled with argon to prevent the insulating glass from fogging. This statement is incorrect!

We explained from the production process of insulating glass that the cause of fog of insulating glass is more than air leakage due to sealing failure, or water vapor in the cavity can not be entirely absorbed by the desiccant when the sealing is intact. Under the effect of indoor and outdoor temperature differences, the water vapor in the cavity condenses on the glass surface and produces condensation. The so-called condensation is like ice cream we eat at ordinary times. After we dry the water on the plastic packaging surface with paper towels, there are new water drops on the surface because the water vapor in the air condenses on the outer surface of the ice cream package when it is cold (i.e. temperature difference). Therefore, the insulating glass will not be inflated or fogged (dewed) until the following four points are completed:

The first layer of sealant, i.e. butyl rubber, must be uniform and continuous, with a width of more than 3mm after pressing. This sealant is connected between the aluminum spacer strip and the glass. The reason for choosing butyl adhesive is that butyl adhesive has water vapor permeability resistance and air permeability resistance that other adhesives cannot match (see the following table). It can be said that more than 80% of the water vapor penetration resistance of the insulating glass is on this adhesive. If the sealing is not good, the insulating glass will leak, and no matter how much other work is done, the glass will also fog.
The second sealant is AB two-component silicone adhesive. Considering the anti-ultraviolet factor, most door and window glasses now use silicone adhesive. Although the silicone adhesive has poor water vapor tightness, it can play an auxiliary role in sealing, bonding, and protection.
The first two sealing works have been completed, and the next one that plays a role is the insulating glass desiccant 3A molecular sieve. The 3A molecular sieve is characterized by absorbing only water vapor, not any other gas. A sufficient 3A molecular sieve will absorb the water vapor in the cavity of the insulating glass, and keep the gas dry so that fog and condensation will not occur. The high-quality insulating glass will not have condensation even under an environment of minus 70 degrees.
In addition, the fogging of insulating glass is also related to the production process. The aluminum spacer strip filled with molecular sieve shall not be put for too long before laminating, especially in the rainy season or in spring like in Guangdong, the laminating time shall be controlled. Because the insulating glass will absorb the water in the air after being placed for too long, the molecular sieve saturated with water absorption will lose its adsorption effect, and fog will be generated because it cannot absorb the water in the middle cavity after lamination. In addition, the filling amount of the molecular sieve is also directly related to the fogging.

The above four points are summarized as follows: the insulating glass has been sealed well, with enough molecules to absorb the water vapor in the cavity, attention should be paid to the control of time and process during production, and with good raw materials, the insulating glass without inert gas can be guaranteed to be free of fog for more than 10 years. So, since inert gas can’t prevent fog, what’s its role? Taking argon as an example, the following points are its real functions:

• 1. After argon gas filling, the internal and external pressure difference can be reduced, the pressure balance can be maintained, and the glass cracking caused by the pressure difference can be reduced.
• 2. Inflation of argon can effectively improve the K value of the insulating glass, reduce the condensation of the indoor side glass, and improve the comfort level. That is, the insulating glass after inflation is less prone to condensation and frosting, but non inflation is not the direct cause of fogging.
• Argon, as an inert gas, can slow down the heat convection in the insulating glass, and also can greatly improve its sound insulation and noise reduction effect, that is, it can make the insulating glass have better sound insulation effect.
• 4. It can increase the strength of large area insulating glass, so that its middle will not collapse due to lack of support.
• 5. Increase the wind pressure strength.
• Because it is filled with dry inert gas, the air with water in the middle cavity can be replaced to keep the environment in the cavity more dry and prolong the service life of the molecular sieve in the aluminum spacer bar frame.
• 7. When low radiation LOW-E glass or coated glass is used, the inert gas filled can protect the film layer to reduce the oxidation rate and extend the service life of the coated glass.
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• In all LEAWOD products, insulating glass will be filled with argon gas.
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• LEAWOD Group.
• Attn：Kensi Song
• Email：scleawod@leawod.com