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You should know the 9 questions of insulating glass two-component sealant.

Some glass deep-processing enterprises often encounter the problem of two-component glue application of insulating glass when they are producing and processing insulating glass, especially: how to judge whether the mixing is uniform when the insulating glass two-component glue is injected, what should do when many bubbles appear during the glue application and what are the reasons for the poor adhesion between the glue and the substrate... LIJIANG Glass has sorted out the popular problems encountered when applying sealant on insulating glass for the reference of glass deep processing enterprises.

1. What should I do if there are a lot of bubbles when the glue is applied?

Figure 1 The bubbles appear in glass

Figure 1 The bubbles appear in glass

In general, the causes of bubbles and their solutions are as follows:

(1) Reason: bubbles generated during glue injection;

Solution: The glue seam is flat and the glue is evenly injected;

(2) Reason: The proportion of component B is too high, the reaction is too fast, and the bubbles cannot be completely discharged;

Solution: Reasonably adjust the relative proportions of components A and components B, and especially in the gluing process, could using the automatic insulating glass sealing robot equipment to automatically mixes two-component glue.

(3) Reason: there are bubbles in the glue itself;

Solution: replace with good quality sealant;

(4) Reason: During the construction of the weather-resistant adhesive, the foam rod was damaged and deflated;

Solution: try not to damage the stuffing foam stick, with the damaged side facing inward;

(5) Reason: the glue seam is wet;

Solution: Ensure that the glue joint is dry during construction.

2. The door and window glue appears cracking and chalking

In engineering projects, cracking and powdering of the door and window adhesive (see Figure 2 and Figure 3) are serious quality problems, which will lead to the failure of the door and window adhesive seal, resulting in water leakage and air leakage.

Figure 2 The cracks in door and window glue

Figure 2 The cracks in door and window glue

Figure 3 The window and door glue appears chalking and cracking

In general, the causes and solutions for cracking and chalking are as follows:

(1) Reason: If the glue injection depth of door and window glue is not enough, the glue is too thin or too thin locally, and the cured glue seam cannot withstand the displacement and deformation caused by an external force and cracking may occur;

Solution: Due to the different sizes of door and window joints, the glue injection size of the door and window glue should be adapted to the size of the door and window joints to ensure that the door and window glue and the edge substrate have sufficient bonding area and bonding thickness.

(2)Reason: The use of inferior door and window adhesives. To reduce costs, some door and window adhesive manufacturers have greatly reduced the content of silicone base polymers, filled a large amount of cheap mineral oil and powder fillers, and produced oil-filled door and window adhesives. This kind of door and window glue will not have obvious problems when it is first used, but because the mineral oil filled in the glue is an alkane substance and has poor compatibility with the silicone glue, the mineral oil will migrate out of the glue after some time; and Its silicone content is low, and its aging resistance is poor. After a period of use, the glue will obviously harden, shrink, and even crack and pulverize;

Solution: At present, the quality of the door and window adhesive products on the market is uneven, and a considerable part of the door and window adhesive products in circulation are filled with mineral oil. To avoid the above situation, the brand products with guaranteed quality and no mineral oil filling should be used. When selecting products, reference should be made to the international industry standard "Testing Method for Alkane Plasticizers in Silicone Structural Sealants". Door and window adhesives can refer to this standard method to determine whether they contain alkanes (mineral oil). Another simple method is to put the door and window glue on a flat plastic film and observe it after curing for several hours; if the plastic film shrinks and wrinkles, it means that the door and window glue is likely to contain mineral oil.

3. What are the reasons for the poor adhesion between the glue and the substrate?

1) The adhesion test is not done before construction or the construction is not carried out according to the method recommended by the adhesion test, and the construction should be carried out in strict accordance with the method recommended by the adhesion test;

2) During the construction process if the cleaning or primer coating liquid does not conform to the construction process, clean it according to the "secondary coating method", and carry out the next construction within 1 hour; the primer coating liquid should be thin and uniform, and the next step should be carried out within half an hour. construction;

3) After the finished unit is made, if the curing temperature is low or the curing time is short, the rubber tapping test shall prevail to determine the curing time of the finished unit. When the curing temperature is low, the curing time may take 5 to 7 days. In addition, the application of primer can shorten the curing time;

4) There are many batches of materials (aluminum, glass, sealant, cleaning agent, primer, etc.) used in the construction process, and there may be differences. Strictly use materials that are consistent with the adhesion test. In the production process, each time the material enters the factory needs to be randomly tested on-site.

4. How to choose the insulating glass secondary sealant?

The insulating glass secondary sealant of point-supported glass curtain walls must also use silicone structural sealant; the insulating glass secondary sealant of the large-size open-frame curtain wall is recommended to use insulating glass silicone structural adhesive; doors and windows and ordinary open-frame curtain walls use hollow glass Glass secondary sealant can choose insulating glass silicone sealant or polysulfide sealant.

As we all know, polysulfide glue has poor resistance to ultraviolet aging. If polysulfide glue is used as the insulating glass for secondary sealing, the bonding surface will be exposed to sunlight for a long time, and the phenomenon of degumming will occur. Therefore, the secondary sealant for an insulating glass of hidden frame curtain wall and semi-hidden frame curtain wall must use silicone structural sealant, and the size should be calculated according to the international industry standard "Technical Specification for Glass Curtain Wall Engineering", and the minimum bonding width should not be less than 7 mm.

Users should choose suitable insulating glass secondary sealant products according to the specific application of insulating glass. Under the premise that the quality of the sealant is qualified, as long as it is properly selected and used, it is possible to manufacture insulating glass with a service life that meets the requirements of use. However, if selected and used improperly, even the best sealant may produce unqualified insulating glass. When choosing the secondary sealant, especially the silicone structural sealant, it is necessary to comprehensively consider the functional requirements of the insulating glass, the compatibility with the primary butyl sealant, and the performance of the silicone sealant should satisfy with relevant standard requirements.

5. Why does the surface of the silicone adhesive change color after curing?

If the materials used in the project are incompatible with the sealant, it will cause the glue to cure for some time, and the color of the glue will appear chromatic aberration.

Figure 4 The insulating glass secondary sealing silicone structural adhesive

Figure 4 The insulating glass secondary sealing silicone structural adhesive

Figure 5 The surface of the silicone adhesive change color after curing

Figure 5 The surface of the silicone adhesive change color after curing

(1) Contact with oil-filled rubber (such as some inferior EPDM rubber, neoprene, etc.) can easily lead to local discoloration of the silicone sealant. Conduct a compatibility test before use to determine whether to replace the material in contact with the rubber. It is recommended to use silicone rubber or good quality EPDM rubber and neoprene;

(2) Acidic and alkaline substances such as some exterior wall cleaning fluids, cement slurry, etc. can easily lead to discoloration of the surface of the light-colored silicone sealant, and the cured sealant should avoid contact with acidic and alkaline substances;

(3) The ketoxime-type silicone sealant is prone to overall discoloration in an acidic environment. In an acidic environment, a dealcoholized sealant is selected.

6. How to solve the poor appearance of glue when injecting glue?

After trimming the glue seam, observe the appearance of the glue seam, and find that there are local depressions or granular protrusions, as shown in the following figure:

Figure 6 The appearance of the glue is found to be poor when injecting glue

Causes and solutions:

(1) The dressing time is too long: the time of exposure to the air is too long, which exceeds the dressing time specified by the sealant, and shortens the interval between the glue operation and the dressing operation;

(2) The trimming method is not standardized, and the glue seam is repeatedly trimmed. It is best to trim the glue in place at one time;

(3) After the glue seam is trimmed, the remaining recycled glue is filled into the surface of the glue seam again, the backfill glue is filled in the glue seam, and new glue is applied on the outside;

(4) The quality of the glue is poor, there are particles or dead glue, or the glue has expired, so choose a good quality sealant.

7. Glue injection for aluminum panel curtain wall and glass curtain wall completes the drumming

The bulging phenomenon is a large-area bulge phenomenon on the surface of silicone rubber. When the rubber strip is cut, the interior is solid, as shown in the figure below.

Figure 7 The two-component sealant injection for glass curtain wall completes drumming

Figure 7 The two-component sealant injection for glass curtain wall completes drumming

Causes and solutions of drumming:

When the relative humidity of the environment is low (below 50%RH), the curing speed of the sealant becomes slower, and the time required for the surface of the sealant to cure to a sufficient depth will be longer.

When the surface of the sealant has not been cured to a sufficient depth, If the width of the glue seam varies greatly (this is usually caused by the thermal expansion and contraction of the panel), the surface of the glue seam will be affected and unevenness will appear. After these uneven surfaces are finally cured, the interior is solid, not hollow, which is called the "bulging phenomenon". 

The bulging phenomenon is the result of a combination of factors such as sealant curing speed, ambient humidity, ambient temperature difference, glue seam width, panel material, and size. 

The following methods can be used: 

choose glue with a relatively fast curing speed; 

adopt appropriate shading measures; 

choose a suitable glue application time (gluing when the temperature of the aluminum plate is high); 

The seam is glued for a second time, and the glue seam that is not visible to the human eye can be kept as it is.

8. How to judge whether the mixing is uniform during two-component injection?

Butterfly test: squeeze the mixed two-component glue from the insulating glass two-component spreading machine onto the paper, fold the paper and flatten it, open the paper and check the glued sample. This indicates that the mixing of glue is not uniform, as shown in the following figure:

Figure 8 The the mixing is uniform during two-component injection

Figure 8 The the mixing is uniform during two-component injection

Causes and solutions for uneven mixing:

(1) impurities are blocking the pipe in the glue machine, clean the mixing system, hose, and glue gun of the glue machine;

(2) If the parts in the melter are damaged, replace the mixing system, hose, and gun of the melter;

(3) If There is a problem with the valve air pressure, adjust the valve air pressure to a suitable value.

9. What are the reasons for the slow curing of sealant?

(1) The temperature is low, and the construction temperature of the sealant should be kept at 10~40℃. If the temperature is low, it is necessary to extend the curing time, or take heating measures;

(2) Low humidity (one-component product), the construction humidity of the sealant should be kept at 50~80%. If the humidity is too high, it is not easy to remove stickiness;

(3) The glue seam is too narrow and too deep (one-component product), because the one-component sealant reacts with the moisture in the air, and gradually solidifies from the surface to the inside. Therefore, the design size of the glue seam should be reasonable;

(4) B component is too small (two-component product), increase the proportion of B component;

(5) If the sealant has expired or the quality is defective, check the production batch number of the glue to confirm whether the glue is within the shelf life. If there is a problem with the quality of the glue, replace the sealant;

(6) The curing speed of different types of glue is different. It is necessary to understand the difference in the curing speed of glue. Two-component > single-component acid glue > single-component ketoxime type > single-component alcohol type glue, choose according to to needs. In the process of use, there are some differences in the curing speed of different brands of glue.

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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