Why does insulated glass fail?

Insulated glass has been widely used in buildings as energy-saving transparent structural parts of building exterior walls, and has many applications in other industries such as trains, airplanes, refrigeration equipment, greenhouses and other industries. Due to insufficient attention paid to the sealing of insulating glass in the production process, it is very easy to cause the sealing failure of insulating glass and lose the energy-saving performance of insulating glass.

The direct cause of affecting the effective service time of insulating glass is the gathering speed of moisture in the middle layer. There are many factors that affect the rate of moisture accumulation in the middle layer, such as material performance, manufacturing process and control, installation method, environmental aging, etc. The dew point of insulating glass refers to the temperature when the humidity of the air sealed in the air layer reaches saturation. When the temperature is lower than this temperature, the water vapor in the air layer will condense into liquid or solid water.

The higher the water content, the higher the dew point temperature of the air. When the temperature of the inner surface of the glass is lower than the dew point of the air in the air layer, the moisture in the air in the hollow cavity will accumulate in the hollow cavity of the insulating glass, causing the dew point to rise. When the ambient temperature drops and the temperature of the inner surface of the glass is lower than the dew point of the air layer, the water vapor in the air layer will condense or frost on the inner surface of the glass (condensation occurs when the temperature of the inner surface of the glass is higher than 0°C, and when the temperature of the inner surface of the glass is lower than 0°C ℃ frost). Condensation or frost on the inner surface of the glass will seriously affect the perspective of the insulating glass and reduce the heat insulation effect of the insulating glass. At the same time, long-term condensation will cause mildew on the inner surface of the glass or return to alkali to produce white spots. , Seriously affect the use of insulating glass. It is mainly caused by the moisture from the outside entering the air layer and cannot be absorbed by the desiccant. The following three reasons can cause the dew point of insulating glass to rise:

 (1) Impurities in the sealant or capillary pores that exist due to improper extrusion during the injection process, under the action of the pressure difference or concentration gradient inside and outside the air layer, the water in the air and oxygen enters the air through gas circulation or diffusion In the layer, the moisture content in the air layer of the insulating glass is increased.(2) Moisture diffuses into the air layer through the polymer (butyl sealant is generally a high molecular polymer). Any polymer is not absolutely airtight, and the sealants usually used for insulating glass include: butyl rubber, polysulfide rubber, silicone structural adhesive, etc. For these polymer materials, the existence of fugacity difference (pressure difference or concentration difference) on both sides constitutes the driving force for isothermal diffusion of the polymer.(3) The effective adsorption capacity of the desiccant is low. The effective adsorption capacity of the insulating glass desiccant refers to the adsorption capacity of the desiccant after it is sealed in the air layer. It is a function of factors such as the performance of the desiccant, air humidity, filling capacity, and time in the air. The desiccant must have a strong adsorption capacity. If the adsorption capacity of the desiccant is poor, it cannot effectively absorb the moisture that enters the air layer through diffusion, which will cause moisture to accumulate in the hollow cavity, the moisture pressure will increase, and the dew point of the insulating glass will increase.

To improve the service life of insulating glass and prolong the effective use time to meet the standard requirements, it should be controlled from various links such as material selection, processing and manufacturing, structural design and installation.

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