1. Causes and prevention methods of blistering in weather resistant adhesive seams
Based on the research of our company's technical experts, we have identified the following causes of blistering in the adhesive seam of a certain enterprise user who experienced severe blistering when using our company's weather resistant adhesive:
1、 The impact of various operations during construction may cause blistering
1. The humidity of the adhesive joint and substrate is high, and there is rainwater;
2. Cut the foam rod carelessly during construction;
3. The selection of foam rod is wrong, and the foam rod with low density must be closed type foam rod conforming to relevant specifications;
4. The thickness of the adhesive application is not enough or too thin;
The above factors can be avoided. During construction, ensure that the adhesive joint and the base material are dry and clean. Pay attention not to scratch the foam rod during operation. Select the appropriate foam rod according to the size of the joint.
2、 Excessive temperature difference can cause blistering in the adhesive seam.
Firstly, let's talk about the situation in summer. During the day, the temperature is very high and the humidity is high. If you work in the morning or afternoon, it is particularly easy to foam because silicone weather resistant adhesive solidifies by absorbing water from the air under certain temperature conditions. When applied in the morning or afternoon, the curing speed of silicone gel is very fast. During the curing process of silicone gel, chemical substances will be released to form gas, which cannot immediately escape from the gel when gathered together. This can cause blistering, which usually occurs between the sunny side of the curtain wall and the long side of the curtain wall component. Applying glue in the evening when the sun sets can alleviate this phenomenon.
Due to the large temperature difference between day and night in winter, the temperature is low, and the climate is relatively dry, which may cause this phenomenon. In winter, the solidification of colloids takes a long time. After the construction of colloids, when they are not fully cured, each unit component of the curtain wall itself has a certain displacement. In addition, the large temperature difference between day and night produces a greater displacement. When the colloids are not fully vulcanized, their resistance to displacement is poor, which leads to the phenomenon of weather resistant adhesive joint bulging.
The above phenomenon only affects the aesthetics of some curtain wall adhesive joints, but does not have any adverse effects on the performance indicators of the gel. This phenomenon will be alleviated as the temperature difference decreases.
Due to the excellent weather resistance and strong high and low temperature resistance of silicone weather resistant adhesive, it is recommended to construct under the following conditions:
1. Please avoid construction on rainy days and pay attention to the weather conditions during the adhesive application period, as there will be no rainy days
2. When applying adhesive, it is necessary to ensure that the adhesive seam and the substrate in contact with the adhesive are dry
3. Construction is carried out during the period from 11am to 3pm in winter, and in the morning or evening in summer
4. Conduct a test before construction, squeeze out the adhesive to observe the curing condition, determine the surface drying time, and trim the surface within the surface drying time
2. What is the reason for the yellowing of neutral transparent adhesive?
Answer: Yellowing of neutral transparent adhesive is due to defects in the adhesive itself, mainly caused by the cross-linking agent and tackifier inside the neutral adhesive. The reason is that these two raw materials have an "amino group", which is very easy to cause yellowing. Many imported glass adhesives also have the phenomenon of yellowing due to this. In addition, if neutral transparent adhesive is used together with acidic glass adhesive, it may cause the neutral adhesive to turn yellow after curing; It may also be due to the prolonged storage time of the adhesive or the reaction between the adhesive and the substrate.
3. Why does neutral porcelain white glue turn pink? Some adhesives turn back to porcelain white after a week of curing?
Answer: Alcohol based neutral adhesives may exhibit this phenomenon, which is caused by the production of titanium chromium compounds as raw materials. The titanium chromium complex itself is red, and the porcelain white color of the adhesive is the titanium dioxide powder in the adhesive that plays a color matching role. But glue is an organic matter, and most organic chemical reactions are Reversible reaction, as well as side reactions. Temperature is precisely the key to causing these reactions. As the temperature increases, a positive reaction occurs, causing a change in color. However, when the temperature stabilizes, the reaction proceeds in the opposite direction, restoring its original appearance. Having a good grasp of production technology and formula should prevent this phenomenon from occurring.
4. Some domestic transparent adhesives turn porcelain white after five days of printing? Why does neutral green adhesive change to porcelain white color after construction?
Answer: This should also be a quality issue with the adhesive, which belongs to the selection and verification of raw materials. Because some domestic adhesives contain plasticizers that are easily volatile; Some adhesives have a lot of reinforcing fillers added inside, and when the plasticizer evaporates, the rubber strip is stretched due to shrinkage, showing the color of the filler (all fillers in neutral adhesives are white). Various colored adhesives are made by adding pigments to turn them into various colors. If there is a problem with the selection of pigments, the color of the adhesive will change after construction; Alternatively, if the color adhesive is applied too thinly during construction, the inherent slight shrinkage of the adhesive during the curing process may cause the color of the adhesive to become lighter. In this case, it is recommended to maintain a certain thickness (3mm or more) when applying the adhesive.
5. Why is it that the back of the mirror is coated with glass glue, and after a period of time, there are spots or glue marks on the mirror surface?
Answer: There are usually three different back coatings for mirrors in the market: mercury, pure silver, and copper. The common phenomenon of speckles appearing on the mirror surface after a period of adhesive application is that the user has used acidic glass adhesive, which usually reacts with the above materials, causing speckles to be seen on the mirror surface. Therefore, we emphasize the use of neutral adhesives, which can be divided into alcohol type and ketoxime type. If ketone oxime type neutral adhesive is used for the mirror with a copper bottom, ketone oxime will slightly corrode the copper material. After a period of construction, corrosion marks can be seen on the mirror surface at the adhesive application point behind it. If alcohol type neutral adhesive is used instead, this phenomenon will not occur. The above are all due to improper material selection due to the diversity of substrates. Therefore, it is recommended that users conduct a compatibility test before using the adhesive to see if it is compatible with the material before using it. Choosing appropriate glass adhesive products can avoid unnecessary losses.
6. Some glass adhesives come out in salt sized particles, and after curing, some particles will automatically dissolve. Why?
Answer: This is a question about selecting the raw material formula for the adhesive. Because some adhesives contain cross-linking agents that crystallize in low temperature environments, the cross-linking agent coagulates in the rubber bottle, and after being knocked out, particles of the size of salt powder can be seen. However, it gradually dissolves, so the particles will automatically dissolve after solidification. This situation has little impact on the quality of the adhesive. This situation is mainly due to the significant impact of low temperature.
7. Some domestic adhesive is applied to glass and has not dried for 7 days. What is the reason?
Answer: This situation mostly occurs during cold weather. 1、 Excessive glue application results in slow drying. 2、 The construction environment is affected by adverse weather conditions. 3、 The adhesive has expired or has problems. 4、 The glue is slightly soft and feels like it won't dry thoroughly.
8. What is the reason for the bubble sound that occurs when some domestic glass adhesives are applied?
Answer: There may be three reasons: firstly, the packaging technology is not up to par, and air is mixed in the plastic bottle; 2、 A few unscrupulous manufacturers intentionally do not press the bottom cap of the bottle tightly, leaving air in the bottle but giving people a feeling of sufficient glue content; 3、 Some domestic adhesives are not 100% silicone adhesives, and the added filling material will have a slight chemical reaction with the PE soft glue of the glass rubber packaging bottle, causing the rubber bottle to swell and increase. The air retained in the space seeps into the adhesive slurry, creating gaps, and making a sound of bubbles during the application process. The effective way to overcome this phenomenon is to switch to hard bottle packaging and pay attention to the storage environment of the product (in a cool place below 30 ℃).
9. Why do some neutral adhesives appear many bubbles when they solidify at the junction of concrete and metal window frames in summer, while others do not? Is it a quality issue? Why hasn't there been a similar phenomenon before?
Answer: Many brands of neutral adhesives have experienced similar phenomena, and after careful testing and repeated experiments, it has been confirmed that it is not a quality issue with the adhesive. Because there are two types of neutral adhesives: alcohol type and ketoxime type, and the methanol contained in alcohol type adhesives during the curing process will release gas (methanol starts to evaporate at around 50 ℃), especially when exposed to direct sunlight or high temperatures, the reaction is more intense. In addition, concrete and metal window frames are difficult to ventilate, and due to the high temperature and humidity in summer, curing will be faster. The gas released by the adhesive can only escape from the incompletely cured adhesive layer, and bubbles of different sizes will appear on the cured adhesive strip. During the curing process, ketone oxime neutral adhesive will not release gas and will not produce bubbles. However, the disadvantage of ketoxime type neutral adhesive is that once the technology and formula are not well processed, there is a chance of shrinkage and cracking during the curing process in winter when cold. If the technology is good and the formula is qualified, this phenomenon does not occur. Of course, the price of ketone oxime type neutral adhesive is slightly higher than that of alcohol type.
The reason why similar phenomena did not occur in the past is that in the past, construction units rarely used silicone adhesive in such places, and usually used acrylic waterproof sealing materials. Therefore, the phenomenon of silicone neutral adhesive foaming is not very common; In recent years, silicone based sealants have gradually been widely used, which greatly improves the engineering quality level. However, due to a lack of understanding of material characteristics, improper material selection has led to the phenomenon of sealant foaming.
To solve such problems, attention should be paid to the following points: firstly, the most cautious approach is to conduct local use testing first to observe whether it meets the needs of use (usually the reaction can be seen two or three days after glue application); 2、 Distinguish between usage time and substrate type, and choose the appropriate neutral adhesive for use: choose ketone oxime type in summer and alcohol type in winter; 3、 Keep the construction surface clean and dry; 4、 When applying glue in summer, it is advisable to avoid high temperature periods (above 35 ℃) and direct sunlight, and it is generally more suitable in the evening; 5、 Similar projects can be tracked by the manufacturer's technical personnel.
10. How to do Compatibility testing?
A: Strictly speaking, the Compatibility testing between adhesives and building substrates should be carried out in the national recognized building materials testing departments. However, due to well-known reasons, it takes a long time to obtain results in these departments and costs a lot. Of course, if there is such a necessary project, the inspection report of a competent national authoritative testing agency must be used to determine whether to use a building material product. For general projects, the base material can be provided to the manufacturer of glass adhesive for Compatibility testing. The test results can be obtained after 45 days for structural adhesive and 35 days for neutral adhesive and acid adhesive. The simplest and fastest way is for users to apply glass adhesive on a small amount of substrate themselves, observe the surface effect after complete curing, and manually test its peel strength to determine whether the adhesive force, tensile force, and other properties of the glass adhesive product meet the needs of use.
11. Why is acid adhesive easy to peel off when used on cement?
Answer: This is actually the most fundamental issue in the application of glass adhesive. Acid adhesive produces acetic acid during solidification, which reacts with the surface of alkaline materials such as cement, marble, and granite, forming a chalky substance that causes detachment.
12. What is the reason for surface wrinkling after curing of neutral adhesive?
Answer: There are generally several reasons: (1) the expansion coefficient of the substrate is relatively high; （2） There is displacement or vibration; （3） Some domestic adhesives themselves are too thin