Common Problems and Solutions of Curtain Wall Glue Construction

Curtain wall glue is an indispensable material in construction engineering. The curtain wall structure of the whole building needs to use it, which can be described as "invisible hero". Curtain wall glue high strength, anti-stripping, impact resistance, simple construction process, widely used in construction and installation, decoration, sealing, structural adhesive and other fields. The development direction of modern architecture will be design standard (standard, construction mechanization, prefabrication of components (light weight, high strength and multi-function of building materials. The wide application of curtain wall engineering glue will speed up the process of the four modernizations, and it is of great significance in improving the construction speed, beautifying the building, improving the construction quality, saving working hours and energy, reducing pollution and so on. Therefore, curtain wall glue has become one of the important chemical building materials. What common problems will be encountered in the construction of curtain wall engineering glue that plays a key role? How do we deal with it?

1. Under what circumstances do high-strength structural adhesives need expert argumentation?

When the silicone structural sealant for glass curtain wall is designed beyond the standard, the curtain wall project needs to use Baiyun brand ultra-high performance silicone structural sealant to improve f1 value (strength design value of silicone structural sealant under wind load or earthquake), f2 value (strength design value of silicone structural sealant under permanent load), δ value (displacement bearing capacity of silicone structural sealant, solve the problem that the design width or thickness of silicone structural adhesive exceeds the specification value encountered in the design process. The feasibility of this super-standard design requires Party A to apply to the Housing and Urban-Rural Development Department of the province where the project is located, and the Housing and Urban-Rural Development Department will arrange time and appoint an expert group to conduct expert argumentation.

2. What is the effect of long-term soaking in water of structural adhesive and gum? How long will it affect the performance?

Both structural adhesive and weather-resistant adhesive belong to silicone sealant (due to the molecular structure of silicone sealant, some chemical bonds will hydrolyze and break under the condition of long-term soaking in water, resulting in bonding failure. In the GB16776 "building silicone structural sealant" standard, silicone structural sealant needs to do adhesion test after curing, soaking in water for 14 days, still good adhesion. In the American standard ASTM 1184, the structural sealant needs to undergo 5000 hours of water UV detection, and the Baiyun brand structural adhesive can pass the test without any problems. However, according to different formulations of silicone rubber, soaking in water for several months to several years will affect the performance. In practical engineering cases, silicone sealant is not suitable for long-term soaking in water environment, such as aquariums and other underwater seams.

3. Can the structural adhesive made of unit board glass play a waterproof and sealing role?

The structural adhesive made of unit plate glass can play a certain role in waterproof and sealing. However, the design of the curtain wall cannot meet the requirements of waterproof and sealing. It still needs external weather-resistant sealant to meet the sealing requirements. Moreover, the structural adhesive soaked in water for a long time will also affect its cohesiveness and reduce the safety of the curtain wall. If the structural adhesive is used as weather-resistant sealant, its displacement ability may not meet the displacement requirements of curtain wall joints, and the sealing durability is not as good as the special weather-resistant sealant.

4. The relevant units in the United States have done experiments. The experimental results show that with the increase of the strength value of the structural adhesive, its life will decrease in a geometric shape. Is this the case? Why?

The improvement of the strength value of silicone structural sealant has no effect on its service life. Our ultra-high performance structural sealant SS922 takes 0.28MPa as the strength design value (the national standard is 0.14MPa) and carries out fatigue test according to European standard ETAG002. The strength retention rate is above 95%, and it still has excellent fatigue resistance. The strength design value is improved, and its durability and safety are sufficiently guaranteed.

What should be paid attention to before the use of structural adhesive?

The following points should be noted before use:

a. Whether the structural adhesive is within the shelf life and the brand is correct;

B. Whether the gluing tool is in normal condition;

c. Whether the construction environment and site meet the requirements;

d. Whether the structural adhesive has been tested for adhesion and compatibility with the substrate in contact with it.

6. How to reduce the bonding width of structural adhesive while ensuring safety?

Designed according to regular, the bonding width of structural adhesive is calculated according to JGJ 102 Technical Code for Glass Curtain Wall Engineering. If the bonding width of the structural adhesive is reduced, the design needs to be changed, such as reducing the plate grid, reducing the weight of the glass, etc. According to the unconventional design, experts need to demonstrate, under the premise of ensuring safety, the use of ultra-high strength structural adhesive to reduce the bonding width.

7, minus 5 degrees structural adhesive can also play?

The construction temperature of building silicone structural adhesive should be 10 ℃ ~ 40 ℃. When the temperature is lower than 10 ℃, the bonding between the structural adhesive and the substrate will slow down, and even there will be no bonding. Therefore, when the temperature is minus 5 degrees, we should strengthen the construction quality control, through the tapping test to determine whether the bonding is good: if the bonding is good, we think it can be constructed; if the bonding is not good, then we need to use appropriate Solvent and primer to improve adhesion.

8. After the surface of the structural adhesive is cured, there is no elasticity and cracks on the surface by hand?

Baiyun Chemical Expert Group Answer: The structural adhesive should have certain elasticity and strength after curing, and the surface of the adhesive should be smooth and free of cracks. If there is no elasticity and cracks, the quality of the structural adhesive on the surface is unqualified and should not be used.

9. The tearing force of weather-resistant adhesive is not smaller than that of structural adhesive. So, can weather-resistant adhesive be used as structural adhesive?

Weather-resistant adhesive cannot be used as structural adhesive. Weather-resistant adhesive requires good displacement ability and high elasticity. In addition to certain elasticity requirements, structural adhesive has the most important requirement for strength. Only when it reaches a certain strength can it bear the self-weight of the plate and long-term wind pressure to ensure the safety of curtain walls such as hidden frame curtain walls and semi-hidden frame curtain walls.

10. How to avoid abnormal mixing ratio (excessive component A or excessive component B) during the construction of two-component silicone structural adhesive?

The products of different manufacturers have different characteristics, and each manufacturer will give the best mixing ratio range of its own products. Mixing within this ratio range can obtain the best product performance. If it exceeds the mixing ratio range recommend by the manufacturer, it will cause a series of problems, such as slow curing, small strength, poor elasticity, poor adhesion, etc. Will seriously affect the safety of the curtain wall!

In order to ensure that the sealant products are mixed in the proportion range recommend by the manufacturer, the breaking time test should be carried out when the glue machine is opened every day, and the breaking time range given by the manufacturer is verified. For example, Baiyun brand two-component structural adhesive in the temperature of 23-25 degrees C, relative humidity of 40-60% conditions, A component and B component in the normal volume ratio of 9:1-11:1 range, pull-off time of 20-60 minutes. Under the above environmental conditions, if the breaking time exceeds this range, the mixing ratio can be considered abnormal.

The breaking time will be affected by the ambient temperature and humidity. Under the actual temperature and humidity conditions, it will sometimes deviate from the time recommend by the manufacturer. For example, when the temperature is low, the breaking time will be extended. However, the pull-off time should generally be stable, and the test results should not fluctuate greatly within a few days. If the temperature or humidity does not change sharply and the pull-off time fluctuates significantly, it is necessary to find out the cause, check whether the equipment is normal, whether the product is normal, etc., and continue construction after eliminating the problem.

Abnormal mixing ratio may be due to equipment setting problems or equipment failure. When using different brands of structural adhesives, you need to pay attention to the mixing ratio of the glue machine. The mixing ratio of two-component silicone structural adhesive recommend from different manufacturers may be different. For example, the volume ratio of Baiyun brand two-component silicone structural adhesive recommend is 9:1~11:1, while that of another manufacturer's product recommend is 7.6:1~10.6:1.

If the mixing ratio of the equipment is set normally and the appropriate breaking time under the corresponding environment is still not obtained, the equipment shall be checked.

The abnormal mixing ratio of structural adhesive will affect the curing of structural adhesive and the strength and cohesiveness after curing, which will seriously affect the safety of curtain wall! Hope that everyone in the process of using glue, pay attention to the test of the break time, to ensure that the mixing ratio of the glue machine is normal, with good structural glue!

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