1. Causes and prevention methods of blistering in adhesive joints
When an enterprise user uses the weather-resistant adhesive produced by our company, the glue seam appears more serious foaming phenomenon. After the research of our company's technical experts, the following causes of foaming are obtained:
First, the influence of various operations during construction may cause foaming
1. The glue seam and the substrate humidity is large, there is rain;
2. Accidentally cut the foam rod during construction;
3. If the foam rod is not selected correctly, low-density foam cannot be used, and the closed-mouth foam rod must meet the relevant specifications;
4. The thickness of sizing is not enough or too thin;
The above factors can be avoided, in the construction must ensure that the glue joint and substrate is dry and clean, pay attention to the operation can not be scratched foam rod, according to the size of the joint to choose the appropriate foam rod.
Two, the temperature difference is too big cause glue seam foaming.
First of all, in summer, the temperature is very high during the day and the humidity is very high. If the construction is especially easy to bubble in the morning or afternoon, because the silicone weatherproof adhesive is solidified by absorbing the moisture in the air at a certain temperature. When in the morning or afternoon after sizing, the silica gel curing speed is very fast, the silicone gel curing process will release chemical substances to form gas, aggregated together can not immediately escape from the gel. This will cause blistering phenomenon, generally this situation occurs in the facade of the sun and curtain wall assembly size long side of the glue seam, in the evening when the sun goes down sizing, can alleviate this phenomenon.
The phenomenon may be caused by the large temperature difference between day and night, the low temperature and the dry climate in winter. It takes a long time for colloid to cure in winter. When colloid is fully cured after construction, each unit of the curtain wall itself has a certain displacement. In addition, the temperature difference between day and night is too large to produce a greater displacement.
The above phenomenon only affects the appearance of some curtain wall joints, but does not produce any adverse results on the performance indicators of the colloid. The phenomenon will be alleviated with the decrease of the temperature difference.
Because the silicone weatherproof adhesive has excellent weather resistance and strong resistance to high and low temperature, it is recommended that it can be constructed under the following conditions:
1. Please avoid the construction in rainy weather and pay attention to the weather conditions during this period of sizing. It is better to have no rainy day.
2. When sizing, it is necessary to let the glue seam and the glue in contact with the substrate is dry.
3. Work between 11am and 3pm in winter and in the morning or evening in summer.
4 do a test before construction, to observe the solidification of the glue extrusion, determine the table dry time, in the table dry time dressing surface.
2. What is the reason why neutral transparent adhesive turns yellow?
Answer: neutral transparent glue yellowing is the glue itself has defects, mainly caused by the crosslinking agent and viscose agent in the neutral glue, the reason is that these two raw materials with "amine group", amine group is very easy to cause yellowing, many imported famous brand glass glue is therefore yellowing phenomenon. In addition, if the neutral transparent adhesive and acid glass adhesive are used at the same time, it may cause the neutral adhesive to turn yellow after curing; It may also be caused by the long storage time of the glue or the reaction between the glue and the substrate.
3. Why does neutral porcelain white glue turn pink? After some glue is solidified, a week turns back to porcelain white again?
Answer: alcohol-based neutral glue may have this phenomenon, which is caused by the production of raw materials titanium chromium compound. Titanium chrome compound itself is red, and the glue of porcelain white color is titanium dioxide in the glue in the role of color. But glue is organic matter, and organic chemical reaction is overwhelmingly reversible reaction, there are side reactions. Temperature is exactly the key to causing these reactions. When the temperature is high, there is a forward reaction that changes the color, but when the temperature cools down and stabilizes, the reaction goes back to the original shape. Production technology and formula grasp well, should be able to avoid this phenomenon.
4, some domestic transparent glue, five days after playing out porcelain white color? Neutral green glue after the construction of porcelain white color, why?
Answer: this also should be the quality problem of glue, belong to the problem of raw material selection and verification. Because some domestic glue add plasticizer, volatile; And some glue with more reinforcing filler, when the plasticizer volatilizes, the rubber strip is stretched due to shrinkage, packing color (neutral glue all the filler itself is white). All kinds of color glue is to add pigment to make it into a variety of color, if there are problems in the choice of pigment, glue color will change after construction; Or the color glue is too thin during construction, and the inherent small amount of shrinkage in the curing process will make the color of the glue light. In this case, it is recommended to maintain a certain thickness (more than 3mm) when sizing.
5, why the mirror on the back of the glass glue, after a period of time, the mirror appeared spots or traces of glue?
A: Mirrors on the market usually have three different back coatings: mercury, sterling silver and copper. Common mirror sizing after a period of time, the mirror appears speckled, this situation should be the user used acid glass glue, and acid glass glue usually reacts with the above material, causing the mirror to see speckled. Therefore, we emphasize that neutral adhesive should be selected, and neutral adhesive is divided into alcohol and ketoxime type two. If the copper mirror uses ketoxime-type neutral adhesive, the ketoxime will have slight corrosion on the copper material. After construction for a period of time, the mirror can see the traces of corrosion at the sizing place behind the mirror. If the alcohol neutral adhesive is used, this phenomenon will not occur. The above is due to the diversity of the substrate caused by improper material selection. Therefore, it is recommended that users do a compatibility test before using the glue to see whether the glue is soluble with the material. Select appropriate glass glue products to avoid unnecessary losses.
6, some glass glue when the size of the grain of salt, and some of the particles will automatically resolve after curing, why?
Answer: this is the problem of selecting the raw material formula of glue. Because some glue contains some crosslinking agent, there is crystallization phenomenon in the low temperature environment, crosslinking agent in the glue bottle condensation, hit out after will see the size of salt powder particles, but it will slowly melt, so the solidified particles will automatically resolve. This situation has little effect on the quality of the glue. This situation is mainly affected by low temperature.
7, some domestic glue on the glass, 7 days still not dry glue, what is the reason?
A: This happens most often in cold weather. First, glue is too thick, dry glue is slow. Two, the construction environment impact, bad weather. Three, the glue expired or have a problem. Four, the glue is soft, feel dry.
8, some domestic glass glue in sizing bubble sound, what is the reason?
Answer: there may be three reasons: first, the technology of packing is not up to standard, and air is mixed into the plastic bottle; Two, a small number of black manufacturers deliberately do not press the bottom cover of the bottle, the bottle has air, but give a person with enough glue feeling; Three, some domestic rubber because it is not a hundred percent silicone rubber, which will increase the filling material and glass plastic packaging bottle PE soft adhesive slight chemical reaction, so that the bottle has the phenomenon of swelling, the air retained in the space into the glue slurry to produce a gap, in sizing will play bubble sound. The effective method to overcome this phenomenon is: change to hard bottle packaging, pay attention to the product storage environment (30℃ below the shade).
9. Why do some neutral glue appear many bubbles after curing in the combination of concrete and metal window frames in summer, and some do not? Is it a quality problem? Why hasn't this happened before?
Answer: many brands of neutral glue have had similar phenomenon, after careful testing and repeated experiments confirmed that it is not a quality problem of glue. Because the neutral adhesive has alcohols and ketoxime type two, and alcohols glue in the curing process of methanol will release gas (methanol at 50℃ left and right began to volatilize), especially in direct sunlight or high temperature reaction is more intense. In addition, concrete and metal window frames are difficult to breathe. In addition, the summer temperature and humidity are high, and the curing will be faster. The gas released by the glue can only run out of the adhesive layer that has never been completely cured, and bubbles of different sizes will appear on the cured adhesive strip. And ketoxime type neutral adhesive in the curing process will not release gas, will not produce bubbles. But the disadvantage of ketoxime type neutral adhesive is that once the technology and formula are not handled well, the cold in the curing process in winter will have the opportunity to appear shrinkage cracking phenomenon. The technology is good, and the formula will not have this phenomenon. Of course, the ketoxime type of neutral adhesive is slightly more expensive than alcohol.
In the past, there was no similar phenomenon because in the past, the building construction unit in this place with very little silicone glue, generally often use propylene waterproof sealing material, so the phenomenon of silicone neutral glue foaming is not very common; In recent years, silicone sealant has been widely used, which greatly improves the quality of the project, but because of the lack of understanding of the material characteristics, the improper selection of sealant foaming phenomenon.
To solve such problems, the following points should be noted: first, the most prudent approach is to do local use test to observe whether it meets the use needs (two or three days after the general sizing can see the reaction); Two, distinguish the use of time and substrate type, choose the appropriate neutral adhesive use: summer choose ketoxime type, winter choose alcohol type; Three, keep the construction surface clean and dry; Four, summer sizing should avoid high temperature period (above 35℃) and direct sunlight, generally in the evening is more appropriate; Five, similar projects can be known to the manufacturer's technical personnel tracking.
10. How to do the compatibility test?
Answer: speak from strict sense, the compatibility test between making adhesive and building base material should admit to the country building material test department is carried out, but because of well-known reason, the cycle that sends check to get a result in these departments is longer, cost is high. Has the necessary engineering of course must be enough the national authoritative testing institutions inspection report to determine whether or not to use some building materials products, and general engineering base material can be provided to the glass glue manufacturer do compatibility test, structural adhesive, 45 days neutral glue, acid gel 35 days or so can be concluded that the test result. The simplest and quickest way is that the user can try the glass glue on a small amount of substrate, to observe the surface effect after complete curing and try its peel strength by hand, in order to simply determine whether the adhesive force and tension of the glass glue product meet the use needs.
11, acid glue used in cement why is it easy to fall off?
Answer: This is actually one of the most basic problems in the application of glass glue. Acid glue in the curing of acetic acid, will react with cement, marble, granite and other alkaline materials on the surface, forming a chalky substance, resulting in shedding.
12. What is the reason for the wrinkling of the surface of the neutral adhesive after curing?
Answer: there are several reasons generally: (1) the expansion coefficient of the substrate is larger; (2) There is displacement or vibration; (3) some domestic glue itself is too thin