Discuss the choice of secondary sealant for insulating glass①
Insulating glass (the term "insulating glass" is provided by Google) has been widely used in commercial office buildings, large shopping malls, high-rise residential buildings, and other buildings. It has excellent heat insulation (the term "heat insulation" is provided by Google), energy-saving, and sound insulation. And other performance. The secondary insulating glass sealant plays an important role in maintaining the stability of the insulating glass structure and has a great impact on the quality and service life of the insulating glass. The insulating glass structural sealant is even directly related to the safety of the curtain wall.
Figure 1 Schematic diagram of insulating glass structure
What are the problems caused by the improper selection of the secondary sealant for insulating glass? This article summarizes the hazards caused by the improper selection of the secondary sealant for insulating glass into the following two categories: One is the loss of the use function of insulating glass, and the loss of the original function of insulating glass The other type involves the safety of insulating glass applications, that is, the outer sheet of insulating glass falls.
This article will combine actual cases to introduce readers to the manifestations of the above two types of hazards, analyze the causes, and preventive solutions. At the end of the article, I will introduce several principles for the selection of insulating glass secondary sealants. This issue of Jinan LIJIANG Glass first introduces the first type of problem, that is, the improper selection of the second sealant for insulating glass causes the loss of the function of the insulating glass. The main manifestations of this type of problem include the phenomenon of "iris film" and "oil flow" in insulating glass. "Water accumulation" and "condensation" phenomena, slippage of insulating glass spacers, etc.
1. Insulating glass "iris film" and "oil flow" phenomenon
The so-called "rainbow film" phenomenon of hollow glass refers to the appearance of a "rainbow" oil film inside the hollow glass cavity, as shown in Figure 2.
Figure 2 "Iridescent Film" Phenomenon of Insulating Glass
The "oil flow" phenomenon of insulating glass refers to the appearance of oil spots or oil stains on a sealing butyl rubber (the term "butyl rubber" provided by Google) in the hollow glass wall, as shown in Figure 3.
Figure 3 "Flowing oil" phenomenon of insulating glass
The above two situations are related to the filling of "white oil" in the sealant. "White oil" is commonly known as mineral oil. Mineral oil is a hydro-refined petroleum fraction, which is mainly a mixture of saturated naphthenic and paraffinic hydrocarbons. Its chemical structure is different from that of organic silicon materials and has poor compatibility with silicone sealants. , It will migrate and ooze after a certain period. The "rainbow film" phenomenon of hollow glass is caused by the migration of "mineral oil" into the inner cavity of the hollow glass; and the reason for the "oil flow" phenomenon is that during the migration process of "mineral oil", the hollow glass and a sealing butyl glue are dissolved, resulting in Black oil spots or oil stains.
These "mineral oils" may come from the secondary sealant for insulating glass, and they may also come from the weather-resistant sealant or door and window sealant that comes in contact with the secondary sealant.
Figure 4 Weather-resistant sealant filled with "mineral oil" leads to the "iris film" phenomenon of insulating glass 1
Figure 5 Weather-resistant sealant filled with "mineral oil" leads to the "iris film" phenomenon of insulating glass 2
The project in Figure 4 and Figure 5, after sampling, testing, and analysis, confirmed that the weather-resistant sealant was filled with a large amount of "mineral oil", which caused the "rainbow film" phenomenon of the insulating glass. It can be seen from Figure 4 and Figure 5 that the oil stains are on the interface of the inner cavity of the insulating glass. Distribution. Since the weather-resistant sealant is in contact with the second insulating glass sealant, the "mineral oil" in the weather-resistant sealant migrates to the second insulating glass sealant, then to butyl rubber, and finally to the inner cavity of the insulating glass. "Iridescent film" phenomenon.
Figure 6 "Mineral oil" filled with door and window sealant causes a sealant of insulating glass to "flow oil"
Figure 6 is filled with "mineral oil" for door and window sealant. The door and window sealant is partly in contact with the secondary insulating glass sealant, so the "mineral oil" in the door and window sealant migrates to the secondary insulating glass sealant in contact with it, and then migrates to a butyl glue, which finally results in partial butyl Glue is dissolved and oil flow occurs.
2. Insulating glass "water accumulation" and "condensation" phenomenon
The phenomenon of "water accumulation" and "condensation" of hollow glass refers to the water vapor entering the cavity condenses into dew (ie "condensation") or pools into water (ie "water accumulation") after the hollow glass seal fails. The phenomenon, as shown in Figure 7.
Figure 7 "Water accumulation" (left) and "condensation" (right) in insulating glass
In the above case, the insulating glass used in the doors and windows of a residential project has a sealing failure. After several years of use, the insulating glass has appeared obvious "condensation" and "water accumulation" phenomena and has lost the effects of heat insulation, sound insulation, and waterproofing.
3. Insulating glass spacer slippage
The insulating glass spacer slip phenomenon refers to the phenomenon that the insulating glass spacer and the second insulating glass sealant are not well bonded, and the internal stress acts on the cavity to slip, as shown in Figure 8.
Figure 8 Slippage of insulating glass spacer
The above case is a residential project at a higher altitude. The doors and windows use large-size hollow glass (the second seal is polysulfide glue). Due to the excessive internal stress, the spacers have slipped. The reason for this phenomenon is The adhesion of polysulfide to the spacer is not as good as that of silicone sealant. When the internal stress is too large, the spacer and the polysulfide are separated.
In this article, Jinan LIJIANG Glass is combined with specific cases to analyze the serious loss of the function of insulating glass. In the next article, Jinan LIJIANG Glass will introduce the second type of problem caused by the improper selection of the second-layer sealant for insulating glass, which involves the safety of the application of insulating glass. At the same time, it will introduce the selection principle of the second-layer sealant for insulating glass.
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