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The FAQ guides and solutions of insulated glass silicone adhesive sealant sealing glue.

1. The acid gum

1.1 The acid plastic bottle will grow taller after being stored for some time. There will even be oil in the bottle if it is deformed. Why?

There are two reasons for this problem, both with glue and glue bottles.

First, the reason for the glue. Except for a few high-grade types of glue, the acid glues on the market now add a certain amount of fillers to different degrees to reduce costs, and the lower the grade of glue, the more fillers are added, and the fillers will react with the plastic bottle, which will cause the plastic bottle to grow taller, deformed and contain oil; for example, high-grade plastic may cause the plastic bottle to react after 9 months, and relatively low-grade plastic may react after 9 months.

Second, the reason for the plastic bottle. The quality of the material of the plastic bottle itself is also the reason for the height. The raw materials used for the bottle body are also good or bad. If the raw materials used are good, the trend of plastic bottle changes is relatively slow. For example, high-quality plastic bottles can be stored for 9-10 months without any reaction; on the contrary, if poor-quality plastic bottles are used, even if they are filled with good plastic, they may deform in 2-3 months.

1.2 Why is the glue thick or dry when looking at the bottom cover of the plastic bottle?

This is mainly generated during the packaging process. Because it takes a certain amount of time from filling the glue to pressing the cover, although the time is short, it also makes the glue come into contact with the air. If the sealant solidifies a lot from the bottom, it is caused by the poor sealing between the bottom cap and the bottle, and it is a quality control problem of the packaging material.

1.3 During the extrusion process of the acid glue, the flow will be cut off or there will be small bubbles, why?

One is caused by the storage temperature being too low: if the acid glue (especially the low-grade glue) is stored at a lower temperature, a lot of air bubbles will be formed. The reason may be that after low-temperature storage, the liquid raw material will form more bubbles due to the change in volume of cold shrinkage, so it is recommended that the storage temperature should not be lower than 0 °C.The second is the formation during the canning process: in normal canning, there are often a small number of small air bubbles at the tail of the sticking rubber, which is difficult to avoid in the current operation method and will not cause substantial use. Influence: If there are more bubbles or cut-offs (large bubbles), it is caused by improper operation, which must be improved and should be avoided. However, this situation also has a probability of occurrence. If such a phenomenon occurs rarely or occasionally, it should be regarded as an accidental event. Large air bubbles should be avoided as much as possible during operation.

1.4 Why does the surface wrinkle after the acid glue is cured?

This is mainly caused when the adhesive layer is too thin when sizing the surfaces of the two substrates. Due to the different thermal expansion and cold contraction rates of different materials, the temperature difference is large, and the incompletely cured glue will deform and wrinkle.Solution: Thicken the adhesive layer. Generally, the thickness of the adhesive layer is about 1 mm during construction. It is recommended to increase the thickness to (1.5-2)mm.

1.5 Why do some acid glues make aluminum discolor after curing?

When the acid glue is cured, it will release acetic acid, which is corrosive to metal materials. The reason why it can be used on aluminum is that the surface of the aluminum is coated with an oxide film or coating, which is protected by a layer of coating. So generally speaking, discoloration of aluminum is not a problem with glue. It should be more about construction operations and the quality of aluminum itself. The quality of aluminum material mainly refers to the unqualified coating layer of the coated aluminum material, such as poor adhesion, too thin a film layer, etc., which will affect the discoloration after sizing; improper construction will also cause discoloration. If the aluminum material is placed in a poorly ventilated environment after sizing, the acetic acid released by the curing of the glass glue cannot be dissipated in time, and the local concentration is too high, which will corrode the aluminum material for a long time and cause it to change color.

Figure 1 Some acid glues make aluminum discolor after curing

Figure 1 Some acid glues make aluminum discolor after curing

1.6 The adhesive strip will turn white or yellow after curing, why?

Yellowing: In more cases, the yellowing of the rubber strip is caused by the influence of other materials in contact with the glass glue. ), due to the poor quality of some glue strips, contact with glass glue makes it yellow, even imported glue is no exception. In general, the rubber strip causes the glass glue to change color. The reason for the analysis may be the materials used in the rubber strip, specifically the reaction between the filler and the acid glue to make the transparent glue change color; it is also not ruled out that the precipitation or volatilization substances are added in the rubber strip, which may contaminate the insulated glass adhesive strips. 

Whitening: The whitening of the glass glue is mainly due to the addition of too much filler in the sealant; if it occasionally turns white, it often occurs in some projects where the glue layer is too thin, so it is recommended to appropriately increase the glass glue when sizing thickness (1.5-3 mm) to avoid similar situations.

1.7 Why some sticky paper and some non-stick paper will appear when the glass glue is applied to the paper?

Glass glue is not used to stick paper, so sticky paper and non-stick paper will not affect the actual use; but the sticky or non-stick paper is related to some characteristics of paper and glass glue. First of all, the material and texture of paper have different effects on sticky paper. If the paper fiber is relatively loose, the glass glue will easily wet the paper and stick to the paper; secondly, the glass glue will also have an influence. The preliminary analysis has a certain relationship with the curing speed. For example, the low-grade glue cures slowly and is easy to stick to the paper.

1.8 Why does the cured transparent acid tape turn white after stretching?

Because solid fillers are added to many acid types of glue to increase the strength, the solid fillers appear white after stretching, so they look white; this situation mostly occurs in domestic glues. Due to cost constraints, the solid fillers used are different from imported glues. There is a certain difference, but it does not affect the performance and actual use of the glass glue.

1.9 Why is the deep curing of insulated glass glue slow?

Deep curing has a lot to do with the use environment. Generally speaking, the curing of glass glue is slow in an environment with low temperature and high humidity; in addition, curing is also slow in a poorly ventilated environment; and there are different grades of the glass glue which cure There is a big difference in speed, especially for domestic glue. The curing speed of low-grade glue is significantly different than that of high-grade glue. This difference is especially obvious when the ambient temperature is low. Therefore, it is recommended that domestic low-grade glue should not be kept near the specified lower limit temperature (5℃).

Figure 2 The deep curing of insulated glass sealant glue

Figure 2 The deep curing of insulated glass sealant glue

1.10 Why does the glass glue shrink after curing?

All sealants shrink after curing, but high-grade and low-grade glues have very different shrinkage rates. For example, high-grade glue shrinks only 5% after curing, and low-grade glue may shrink by 30% or more, this is because low-grade glue is added with filler, and the filler will slowly volatilize in the air, so the more the filler, the higher the shrinkage rate.

1.11 There is a small amount of oil separation on the bottle mouth?

This is a normal phenomenon of long-term storage. Generally, it is stored for more than 3 months, but the probability of this situation is not very high in practice, because the separation of glass glue and oil will only occur after a long period of standing. Because the sales of glue are often in motion, such as transportation, loading, and unloading, warehouse sorting, etc., it is equivalent to continuous stirring, so there will be no layering phenomenon for a long time. The reason for a small amount of oil separation is that the product is composed of liquid raw materials and solid raw materials. Due to their different specific gravity, they will sink under the condition of long-term standing, but because this process is very slow, it does not affect their use. And product performance, this phenomenon also exists in imported rubber.

1.12 Is the vat glue sourer than the imported acid glue?

The difference here is mainly low-grade rubber because the basic materials of domestic low-grade rubber are limited by cost, resulting in a short storage period. To improve the storage period, a variety of additives need to be added, and the taste is strong, but the main release is acetic acid, which is harmless to the human body.

1.13. Why do some glass glues dry too fast and have no trimming time?

This is related to the construction temperature and operation. It is recommended to avoid high-temperature weather during construction and increase the number of trimming times. If the trimming is done after the 2-meter-long seam is originally trimmed, it can be changed to trim the trimming after the 1-meter-long glue seam is finished, which can reduce the excessive surface dryness. quick and detrimental effects.

1.14 There is oil seepage when the adhesive tape hits the paper, why?

First of all, different papers are affected by factors such as texture and material. If some paper fibers are loose, the filler added in the low-grade glue will penetrate the pores, resulting in oil seepage; but after experimental observation, this situation is used in practice. It will not appear in the aluminum and glass, that is, there will be no oil leakage on aluminum and glass, and it will not affect the adhesion, strength, and other properties.

1.15 High-grade glue (including imported glue) is more non-stick than aluminum, why?

Because its curing speed is too fast, the glue does not fully infiltrate the surface of the aluminum material, that is, it cannot penetrate the micropores on the surface of the substrate without sticking. This phenomenon does not affect the normal use of glass glue. There are two main types of high-grade glass glue, one is a large glass curtain wall or a point-type curtain wall. When used here, glass glue only touches glass and does not contact other materials, so it does not matter if it does not stick to aluminum; the other is for glass aluminum alloy. For door and window caulking, glass glue fills the seam between glass and aluminum alloy, although the adhesion between glass glue and aluminum alloy is not good, because of good adhesion to glass, it will not fall off, and it should not be used as a caulking seal. load (that is, do not apply force), so as long as it can adhere to the aluminum alloy, it can play a sealing role.

1.16 Are there crystals in the acid gel?

This phenomenon has only occurred occasionally, mainly caused by the storage temperature being too low, because many additives added to the acid gum system have high freezing points. It becomes crystal and precipitates, so avoid storage temperature too low.

1.17 Acid gel turns red?

This phenomenon has only occurred occasionally, mainly due to the instability of raw materials, so the inspection of raw materials must be controlled.

2. The neutral glue

2.1 The analysis of the cause of blistering

There are many reasons for the foaming of silicone weather-resistant sealants during construction, and it is relatively complicated. It is difficult to use one method and one result to determine the cause of foaming. The silicone structural sealant is generally injected on the automatic insulated glass sealant sealing robot, into the glass deep-processing factory. The environment and operating conditions in the factory are relatively good, and it is easy to meet the external conditions required for the curing of the silicone structural sealant. Silicone weather-resistant sealants are generally completed on the construction site to complete the glue injection work. The construction site environment and operating conditions are poor, and the external conditions required by the silicone weather-resistant adhesive during the curing process are not easy to meet. Climate, environment, operating conditions, and other non-human-changeable reasons have a great impact on the curing quality of silicone weather-resistant adhesives. Therefore, the limitations of the environment and operating conditions of the silicone weather-resistant adhesive determine the main cause of foaming. Some specific situations are analyzed below.

Figure 3 Some reasons for the foaming of insulated glass silicone weather-resistant sealants

Figure 3 Some reasons for the foaming of insulated glass silicone weather-resistant sealants 1

(1) Air is entrained in the glue injection

Silicone weather-resistant glue is generally completed on the construction site to complete the glue injection work, and the working conditions are poor. Workers stand on the scaffold to inject glue, the uniformity of glue injection is not easy to control, and the air is easily trapped in the glue seam. After the glue is applied, the surface of the glue seam is scraped and pressed, and the trimming is smooth. The pads in the glue seam are generally made of closed-cell polyethylene foam rods. The air wrapped in the glue seam is not easy to overflow. The outer ridge tension and the weather-resistant glue seam are generally wider and the thickness is smaller, the weather-resistant glue provides high displacement ability, the hardness is low, and the glue is very soft before curing. The tension of the compressed air slowly props up the glue seam to foam. This phenomenon is more likely to occur in the application of weather-resistant adhesives that can provide more than ±25% of the glue seam displacement ability. On the contrary, some weather-resistant adhesives that allow lower displacement capacity have higher hardness and are thicker before curing. The tension of the compressed air wrapped in the glue seam is not easy to hold the glue to foam. Therefore, the more weather-resistant glue that can provide high displacement capacity, the more attention should be paid to the uniformity of glue injection when injecting glue. Generally, the vertical glue joint can be glued from the bottom to the top, which can overcome some foaming phenomena. What is more important is the proficiency and responsibility of the work operator.

(2) The interface is wet during injection

When working outdoors, rain is often encountered, especially in summer in the northern hemisphere. It rains almost every day. If the interface is wet and not dry after the rain, directly inject glue. When the sun shines on the substrate and glue seam, the temperature inside the interface When rises and the moisture in the glue joint will evaporate, which will cause the uncured, relatively soft glue joint to bulge. Therefore, do not blindly seek progress during construction, wait until the interface is dry, and then inject the glue to avoid the above situation.

(3) Deflate the foam stick

The cushion rods in the glue seam are generally made of closed-cell high-foaming polyethylene foam rods. Due to improper extrusion during placement, the internal airbags are ruptured and the air is released. When the glue is injected, there will be bubbles bulging or some bulging appearance, the solution to this situation, is to cut the foam rod, and the cutting face is inward, and the other is to use an open-cell foam rod or a foamed vinyl foam rod to overcome the above situation. In another case, alcohol-based weathering adhesives release methanol when cured, which reacts with some foam sticks. In such a situation, the problem can be solved by changing the foam stick or ketoxime-type sealant.

(4) Sun exposure when the glue is not cured

The silicone glue cannot be exposed to the sun before it is cured, especially if it is exposed to the sun just after the glue is injected, it will cause honeycomb bubbles to appear inside the glue seam, which will cause the external bulge of the glue seam. It will be more noticeable when using keto glue. In hot summer construction, this situation is not easy to overcome. Avoid sun exposure when using glue injection, which will overcome some blistering. Specific method: inject glue on the west or north side of the building in the morning, and inject glue on the east or south side of the building in the afternoon. After the glue is injected, the glue has been cured for some time, and the surface has been crusted. When it is exposed to the sun again, it has a certain resistance and can overcome some blistering.

(5) The surface temperature of the substrate is too high

When the silicone adhesive is cured, the temperature of the material to be bonded cannot exceed 50°C. This conclusion has been recognized by most silicone adhesive manufacturers. When the surface temperature of the substrate exceeds 50 ℃, the glue will cause foaming in the glue seam. When the weather-resistant caulking of the metal sheet curtain wall is used, the above situation will be encountered. In hot weather, when the metal plate is exposed to the sun, especially the surface temperature of the aluminum plate, the surface temperature will reach 80 °C. At this time, the glue injection can easily cause the glue seam to foam. Therefore, the latter half of the afternoon or cloudy days should be selected to improve the above situation.

(6) The temperature difference between day and night is large, and the thermal expansion and contraction of the interface are large.

This situation is more likely to occur when the aluminum curtain wall is injected with glue. The aluminum plate is a material with a large linear expansion coefficient. In the northern hemisphere, the temperature difference between day and night is large in spring or autumn, and when the sun shines directly on the aluminum plate at noon, the surface temperature of the aluminum plate can be as high as 60℃-70℃, and the temperature at night drops to about 10℃. Large aluminum plates have large thermal expansion and cold contraction, and the joint displacement is large. After the weather-resistant glue is caulked, the actual displacement of the joint is borne by the glue joint. During the curing process, excessive and repeated expansion and contraction displacement will cause Causes foaming of the glue seam, so avoid the direct sunlight at noon when the glue is injected to improve some of the above-mentioned foamings.

(7) The climate in the northern region is dry in spring

Silicone sealants use moisture in the air to chemically react into elastic sealing materials. There is a close relationship between the humidity in the air and the curing speed. The spring climate in the northern hemisphere is dry. After the silicone sealant is injected, the curing time is very long. The uncured silicone sealant is easily affected by the external environment, providing opportunities for various foaming phenomena.

Figure 4 Some reasons for the foaming of insulated glass silicone weather-resistant sealants 2

Figure 4 Some reasons for the foaming of insulated glass silicone weather-resistant sealants 2

2.2 Why is the deep curing of sealant slow?

First of all, the objective conditions of sizing have a great influence on the deep curing speed. For example, the construction environment, temperature, and humidity have a great influence on the curing speed. Too low temperature and too high humidity will significantly slow down deep curing. In addition, there is ventilation on the construction site. If the air circulation is not smooth, it will also affect the deep curing. In addition, the design of the glue joint also has a great impact on deep curing. When the width-to-depth ratio of the glue seam is not appropriate or the depth is too deep, the deep curing will be slower; in general, the deep curing will be slightly slower, and it is not suitable for actual engineering use without quality problems (such as foaming, internal curing, etc.). Influence, the protection period is 21 days, and the thickness of the test specimen is equivalent to that of the actual project, that is to say, the complete curing time recognized by the national standard takes 21 days, and the curing time of our reaction is far less than 21 days (generally more than 5-7 days). In addition, we believe that too fast curing of sealant is not very good for long-term use, because too fast curing is not conducive to releasing the stress caused by the temperature during the curing process, and there are hidden dangers. For example, the curing time of concrete is limited. If it is too fast, it will cause stress concentration and cracking.

2.3 Why does the sealant crack after curing?

There are very few cracks in the middle of the real adhesive strip after curing. Because there are too few cases, and some objective situations are not very clear, it is impossible to accurately judge the cause. The cracking mentioned here mainly refers to the degumming phenomenon on one side of the substrate caused by poor adhesion to the substrate, also called cracking.The reasons for this are mainly as follows (except for inferior glue):Second, there is a reason for the construction, the surface of the substrate is not cleaned or the construction is improper, such as construction before the solvent is dry or the cleaning time is too long and it is polluted.

Figure 5 The insulated glass sealant crack after curing

Figure 5 The insulated glass sealant crack after curing

2.4 The surface of the adhesive strip is wrinkled and uneven after curing, why?

This situation occurs more often when sizing vertical joints. The reason for this analysis should be that in the early stage of sizing, the wetting speed of the glue on the surface of the substrate is slow, that is, the initial adhesion is poor, resulting in the sealant due to its weight. The phenomenon of wrinkling and unevenness caused by sagging; it is recommended to extend the trimming time as much as possible within the allowable range of construction during construction, and at the same time change the trimming operation, use a scraper to trim from the lower end of the glue seam upwards; be careful not to over-extrude when trimming, otherwise It is easy to cause deformation of the cushion foam stick, and then the foam stick will gradually recover, causing the sealant to bulge as a whole.

2.5 Why does porcelain white sealant turn yellow and red?

This happens occasionally with alcohol-based adhesives. The reason for analysis may be the unstable quality of the additives added, or the contamination of accessories or other materials that come into contact with the cured adhesive strip.

2.6 Why does the neutral transparent adhesive (ketoxime type) turn yellow or even red after curing?

Ketoxime transparent glue (including light-colored glue) will turn yellow to varying degrees after curing for about 20 days, and with the increase of time, the yellowing will tend to intensify. The yellowing of ketoxime transparent glue here is not the existence of individual manufacturers It is a problem that exists in the whole industry of a product, including foreign manufacturers. After analysis, it may be due to the addition of a coupling agent with an amino group.Although yellowing is an inherent defect of current products, the curing environment has a great influence on yellowing. First of all, ketoxime-type transparent glue cannot coexist peacefully with acid glue and alcohol-type glue. In less than three days, the ketoxime transparent glue will turn yellow seriously. In addition, placing the cured ketoxime transparent glue in a dark and damp corner will also cause it to turn yellow until it turns red.

2.7 Why does the sealant have poor adhesion to some building materials (such as aluminum, aluminum-plastic panels, steel, etc.)?

First of all, let’s talk about the diversity of building materials: there are many kinds of building materials on the market now, such as aluminum, there are sprayed aluminum, and anodized aluminum. Sprayed aluminum is divided into electrophoresis, fluorocarbon, and other coatings, and the surface properties are different. Therefore, it is necessary to know the advantages and disadvantages of adhesion through experiments. The general raw material of plastic steel profiles is PVC (polyvinyl chloride), and also added Plasticizers and fillers, but now there are many manufacturers, and the materials used are different, so there is also great uncertainty.Let's talk about the instability of sealant: as a chemical product, many factors affecting the quality cannot be directly observed, so we recommend doing a compatibility test before construction.

2.8 Why does the weatherproof glue sometimes dry too fast, resulting in insufficient dressing time?

The surface-drying time of weather-resistant adhesives is 30-40 minutes, which is not short for normal construction, but when the construction environment changes greatly (such as high temperature), the surface-drying time will become faster, so there will be problems that cannot be repaired. In the same way, when the temperature drops, the surface dryness will be prolonged, so if the surface dryness time is moderate when the temperature is high, the surface dryness will be very long when the ambient temperature is lowered, which will make the tack-free time longer, thus affecting the Project acceptance. Therefore, to reduce the influence of fast surface drying, it can be improved by adjusting the number of trimming appropriately.

2.9 Why do I sometimes find a small amount of brittle solid near the bottom of a sealant bottle?

This is a phenomenon that exists in products now. The reason for the formation is that the bottom cap and the bottle body are not tightly sealed, resulting in a small amount of glue curing nearby, and when the glue is cured, it will form a brittle and hard solid when it contacts the plastic. This phenomenon does not occur in contact with other materials. And there will be no quality problems.

2.10 Why are there particles in the sealant?

If there are large particles or large rubber in the sealant, it is a control problem in the production process, which can be solved by strengthening management and control.One is the powder particles because all glues need to be added with reinforcing fillers, the most commonly used are calcium carbonate and silica, which are solid substances, and solids are mixed with liquids. Because the solid particles are small, the surface energy is easily formed. Aggregates, which are difficult to completely disperse in the liquid, form some small particles. The basis for judging the particles of powder is to pick out the small particles in the glue and grind them by hand to see if they are still there. If not, it means that the particles are powder; The glue itself has leveling properties, and the surface can be slowly leveled and covered with some small particles, and the glue application is a super-close observation. If it is viewed from a distance after construction (about a foot away), many particles are difficult to find.

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