As a glass product with mature materials and production technology, insulating glass has guaranteed product quality and is widely used in buildings. Due to management problems of individual insulating glass production enterprises, especially deficiencies in material selection, production process control and construction, product quality problems arise, the most common of which is condensation on insulating glass. In order to avoid this problem, this article will analyze the causes of condensation on insulating glass.

1.Insulated glass dew point

The dew point of insulating glass refers to the temperature at which dew condensation occurs when the gas humidity in the insulating glass spacer layer reaches a saturated state. That is, when the water vapor content is higher, the dew point temperature of the glass is higher. Condensation usually occurs when the temperature of the inner surface of the glass is lower than the dew point of the air in the spacer layer, and water vapor in the air will condense on the inner surface of the glass.

 2.Effect of edge sealing materials on dew condensation in insulating glass

The edge sealing materials are mainly butyl sealant for the inner channel sealant and silicone sealant and polysulfide sealant for the outer channel sealant. Its main function is to bond the various materials that make up the insulating glass to make it a whole. And it has the function of preventing water vapor and other gases from entering the insulating glass spacer layer. Butyl sealant is a one-component sealant based on polyisobutylene rubber. It has extremely low water vapor transmission rate and good adhesion. It and the exterior sealant form an excellent anti-moisture system. , plays an important blocking role in preventing water vapor and other gases in the outside air from penetrating into the insulating glass cavity. The function of the exterior sealant is to bond glass, spacers and other materials into a whole.To ensure the stability of the overall structure of the insulating glass, it must have strong adhesion and mechanical properties. Avoid structural displacement of the insulated glass due to dynamic and static loads during use, thereby ensuring the stability of the anti-moisture system composed of the inner and outer sealants. Therefore, the quality of the two sealants used to protect the insulating glass structure determines the overall quality of the insulating glass and whether condensation occurs.

 3.Effect of spacer materials on fogging and condensation of insulating glass

The main spacer materials include: aluminum spacers, stainless steel spacers, composite spacers, etc. The spacer bar plays the role of carrying desiccant, matching sealing and overall structural strength. Whether the pore permeability of the spacer is excellent directly affects the working ability of the desiccant. The spacer standard stipulates that the pore permeability of the spacer should meet: when the inlet air pressure is maintained at 0.5MPa, the air pressure difference should not be less than 0.1 MPa. Otherwise, the desiccant in the spacer will not be able to absorb water properly. At the same time, the spacer strips should be straight, the side bow and wave curvature should not be greater than 0.2%, the distortion should not be greater than 0.5mm, and should not be deformed. The corners should be flat on the sides to ensure the sealing width and sealing bonding effect of butyl glue.

 4.Effect of Desiccant on Condensation in Insulated Glass

The function of the desiccant is to absorb the water vapor in the insulating glass spacer layer. It not only absorbs the initial water vapor when the insulating glass is produced, but also absorbs the water vapor that continuously penetrates into the insulating glass spacer layer during the use of the insulating glass, so that the gas in the spacer layer Keep it dry to ensure that the dew point of the insulating glass meets the requirements during service.

 5.The influence of production technology on condensation in insulating glass

In the production of insulating glass, the main factors that can affect the condensation of insulating glass include: cleaning of the original glass, frame making, temperature and humidity of the production environment, filling of desiccant, application of butyl sealant, lamination, application of the second sealant, etc. process link.

（1）The original glass sheet was not cleaned thoroughly, causing sweat stains, water stains and residual water droplets to stick to the surface of the original glass sheet; the temperature and humidity control of the production environment was not strict and not dry enough; the bending equipment during frame making caused the back of the spacer to crack, and the butyl The surface of the spacer strips in contact with the sealant is uneven and has concave and convex phenomena, etc., which will become a hidden danger of causing condensation on the insulating glass.

（2）The temperature and humidity control of the production environment does not meet the requirements, the interval between filling the desiccant and closing the sheets is too long, the desiccant package is damaged or the desiccant package is opened for too long, the desiccant filling amount is insufficient, if the desiccant is not filled in accordance with JC/T Implementation of the filling requirements stipulated in the 2071-2011 "Insulating Glass Production Regulations" will also cause condensation on the insulating glass.

（3）The butyl sealant coating must be continuous and even. Before applying butyl sealant, the flatness of the glass tempering and the production quality of the spacer frame should be checked. Discontinuous, broken or uneven butyl sealant coating should not occur. Improvement The bonding strength of butyl glue to glass and spacers prevents condensation on insulating glass caused by this.

（4）The coating depth of the outer sealant is not enough, and the mixing effect of the two-component sealant is not good. It does not meet the requirements of the national standard of "Insulated Glass": the width of the outer sealant of insulating glass should be ≥5 mm; the width of the butyl sealant of the inner channel of insulating glass should be ≥3 mm will cause condensation on the insulating glass.

Through the above analysis, it can be seen that there are many factors that cause dew condensation on insulating glass. In actual production applications, the cause of dew condensation on insulating glass may be one factor or the superposition of multiple factors. Therefore, when condensation occurs in insulating glass, we must first understand the mechanism of condensation in the insulating glass, combine it with the environmental conditions of the insulating glass, and then analyze the materials and processes that cause the problem one by one to determine which part of the insulating glass is the cause of the condensation. If a problem occurs in one link, the specific cause of condensation will be determined after comprehensive analysis, and the corresponding production link will be rectified to avoid the recurrence of quality problems with condensation on insulating glass.