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Influence of many complex factors on the sealing performance of insulating glass

With the development of the economy, the advancement of technology, and the improvement of people's living standards, the insulating glass originally used for high-end buildings, as an effective glass energy-saving structure, has been popularized in ordinary people's residences. However, in the popular use of insulating glass in the past ten years, there are still voices in all aspects that the quality of insulating glass is worrying, ranging from air leakage and water ingress to outer pieces falling off. As a manufacturer of insulating glass processing equipment, Jinan LIJIANG Glass is also willing to extract one of the various raw materials for making insulating glass for in-depth analysis, to call on insulating glass manufacturers to strengthen their quality awareness, pay attention to the selection of raw materials, and protect the interests of users. 

Insulating glass is a glass composite structure, which is composed of 2 or more pieces of glass, which are evenly spaced for effective support and are bonded and sealed around the periphery to form a glass product with a dry gas space between the glass layers (the entry "glass product" is provided by Google ) (quoted from the industry standard "Insulating Glass"). We know that the structure of insulating glass makes it significantly improved in terms of sound insulation, heat insulation, heat transfer coefficient reduction, and energy-saving effect compared with single-piece glass. Therefore, the original monolithic use is presented as a hollow structure when conditions permit. Due to the different purposes of use, the combination of multiple types of functional glass can form tempered hollow, coated (entry "coated glass" provided by Google) hollow glass, Low-E coating hollow glass, laminated hollow glass, silkscreen hollow, fireproof (entry " Fire-resistant glass" provided by Google) insulating glass and more. So many types of use, such a wide range of use, put forward higher requirements for the quality of insulating glass, and also make everyone pay more attention to the sealing performance of insulating glass. For insulating glass, the primary premise for the performance or function of insulating glass is to ensure the sealing of the product, and the guarantee of sealing depends on good raw materials, standardized processing technology, and strict quality management. Among them, the spacer, desiccant, sealant (or composite material) form the edge sealing system of the insulating glass for the glass. In this system, the desiccant is filled in the spacer, the butyl glue is hot-coated on the spacer, the spacer has adhered to the glass through the butyl glue, the outer sealant and the butyl glue are bounded, and the gap around the glass is filled so that One of the edge systems is the barrier of whether the insulating glass is sealed or not. 

In the insulating glass industry or the glass deep processing industry, it is often discussed: 

  • Is the performance of the sealant in the edge system good or bad?
  • What is the water adsorption capacity of the desiccant or molecular sieve?
  • How much should the filling amount of the desiccant be, etc.,

and several discussions have been launched from this. But just as we call the combination of raw materials at the edge a system, the tightness not only depends on each independent factor but also needs to consider the composite factors after the combination, that is, both independent factors and composite factors cannot be ignored. If one has to rank the contribution of raw materials to the sealing performance of insulating glass, it is undoubtedly the butyl rubber that bears the brunt. Because the water vapor transmission rate of butyl rubber is the lowest between silicone structural adhesives and polysulfide rubbers (see Table 1). The core butyl rubber is coated on the spacer by the hot-melt method. If the cleanliness and quality of the spacer cannot be guaranteed, it will directly affect the sealing performance of the final hollow product, that is, the service life. 

Comparison of physical properties of commonly used insulating glass sealants

Sealed formWater vapor transmission rateGas retentionUV resistant propertiesHeat resistanceApplication device methodScope of application
Hot melt butyl glue0.65very goodgoodgoodDevice smear or automaticThe use of insulating glass processing
Polysulfide40-65poorgoodgoodDevice smear or automaticThe use of the second seal of insulating glass
Silicone glue200poorvery goodgoodPump coatingThe use of curtain wall insulating glass second seal

Jinan LIJIANG Glass discusses the composite factor of the adhesion between the spacer and the butyl rubber as an entry point. From Figure 1 and Figure 2, the bonding situation of the butyl rubber can be seen.

Figure 1 The butyl glue and aluminum frame are normally bonded 1

Figure 2 The butyl glue is completely peeled off from the aluminum frame 1

Figure 2 The butyl glue is completely peeled off from the aluminum frame 1

Figure 1 The spacer bar is an aluminum bar, with a smooth surface, no oil stains, and good adhesion with butyl glue. What is seen in Figure 2 is severe peeling of the butyl from the spacer (entry "peeling" courtesy of Google). First of all, the peeling is localized, because we can still see the adhesion of butyl glue on the spacer at the upper and lower positions of the peeling, but the degree of adhesion is not very good. This degree of peeling should be more serious. Because this is a fully peeled state, no glue marks remain on the spacers. Secondly, if there is peeling between the spacer and the butyl glue, there is every reason to believe that there will also be poor adhesion between the spacer and the second sealant. 

We can analyze the poor adhesion of butyl rubber from the following points: 

1. Oxidation of spacers 

Due to the production process or improper storage conditions, the spacer bars are oxidized, as shown in Figure 3. 

Figure 3 The oxidation phenomenon of insulating glass spacer surface 1

Figure 3 The oxidation phenomenon of insulating glass spacer surface 1

Treatment method: If it is the cause of the spacer itself, the incoming inspection of raw materials should be strengthened. In addition to verifying the appearance, the on-machine test can be directly carried out. For the storage conditions of the spacer, pay attention to whether there is any leakage of rain or water. It should be placed separately from the chemicals, and should not be placed directly on the ground, and ventilation should be ensured. In the rainy season, avoid being soaked in rainwater. When using, it is found that there is oxidation and blackening, and batches should be exchanged in time. 

2. The quality of the spacer bars is qualified 

The quality of the spacer bars is qualified, but due to the poor placement environment or use environment, the spacer bars are stained with oil and dirt.

Treatment method: When the spacer is not oxidized, the oil stains attached to the surface are easier to clean up. This lies in the quality requirements of the manufacturer. If we require that the surface of the spacer be decontaminated before coating the butyl rubber, defects can be effectively prevented. The easiest way is to use cotton gauze with alcohol to wipe it.

3. Butyl rubber coating machine 

Butyl rubber coating equipment (the entry "butyl rubber coating equipment" is provided by Google) often uses talcum powder, so even if the spacer strips are of acceptable quality, they are decontaminated before coating, but due to the Excessive talc powder will inevitably contaminate the spacer and affect the bonding between the spacer and the butyl rubber, as shown in Figure 4.

Figure 4 The working site of insulating glass butyl rubber coating machine 1

Figure 4 The working site of insulating glass butyl rubber coating machine 1

Treatment method: Clean the equipment in time every shift, especially the talc and other pollutants on the conveyor belt; or use Jinan LIJIANG Glass' latest LJTB01 Insulating Glass Butyl Extruder Coating Machine, the equipment is driven by a non-stick synchronous belt, no need to apply talcum powder, The glued effect coating is thick and not easy to wear. 

Jinan LIJIANG Glass LJTB01 Insulating Glass Butyl Extruder Coating Machine

4. Spacer bar deformation 

Twisting and uneven surface due to process problems of spacer bars. Such unevenness affects the width of the spacer on a microscopic level, and in the process of applying the butyl rubber, there is no substantial bonding between the butyl rubber and the spacer in some places. 

Processing method: For such problems, it can be picked out by testing in the frame-making process. When the situation is serious, it will affect the normal operation of the butyl rubber machine. Because of its low water vapor transmission rate, butyl rubber has become the guarantee of the sealing performance of hollow products. But "if the skin does not exist, the hair will be attached", if the butyl rubber does not have a spacer that can be well bonded to it, then ensuring the tightness is useless.

For more information about Jinan LIJIANG Glass insulating glass processing equipment and insulating glass processing accessories, please click here to learn more. 

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