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How to correctly choose different displacement capacity of weatherproof sealant?
In the "White Cloud Online" in August, the Baiyun Chemical Group introduced the relevant standards for weatherproof sealants. For different types and different uses of weatherproof sealants, products that meet the corresponding national standards and industry standards should be selected.
According to the previous introduction, we know that the sealants used in building joints are required to withstand the changes in the width of joints caused by the external environment during construction. Therefore, the displacement capability is the main performance indicator. The displacement resistance of weatherproof sealant for curtain wall is generally: 20, 25, 35, 50, +100/-50 and so on. Level 35 is able to withstand changes in the glue gap between ± 35%. So, for different displacement levels of weathering sealant, how should the user choose, how to correctly choose to ensure the long-term durable sealing performance of weatherproof sealant? This issue of Baiyun Online answers questions for everyone.
1, according to the design of the glue joint to select the appropriate displacement capacity of weatherproof sealant
To ensure the long-term durable sealing performance of weatherproof sealants, the first need for proper design of glue joints, if the design itself is a problem, it is difficult to ensure that there is no problem during use. The design of the glue seam mainly involves the matching of seam width and glue displacement capacity and the thickness of the glue seam.
The adhesive seam width of the silicone weatherproof adhesive should not be less than 6mm, and should meet the deformation requirements of the plate. The temperature difference deformation can be calculated according to the “Technical Specifications for Glass Curtain Wall Engineering” JGJ 102 4.3.9, the formula is as follows:
For example: 2 meters long aluminum plate (thermal expansion coefficient 2.4×10-5 / °C), the expected temperature change 80 °C, structural tolerance 3.0mm, the displacement of the sealant used is 25%.
According to the formula above, the width of the glue gap should be greater than 20.4mm.
For the majority of users, under normal circumstances, the width and thickness of the curtain wall joints have been designed, how can we choose the suitable weather resistance rubber displacement capacity? At this point, we can calculate according to the above formula. For example, the width of the designed aluminum plate joint is 20mm. We can calculate the displacement capacity of the required glue and calculate the following:
According to the calculation above, we need to select a glue with a displacement capacity of more than 25.6%. In this case, selecting 25-level displacement glue is not appropriate, and we need to select 35-level displacement capacity or higher displacement weather-resistance sealant.
2, choose a higher displacement capacity of weathering sealant
If the size of a project's glue joints is designed according to level 25, a product with 35 or higher displacement capacity is used during construction, and the seal durability will be better, because the displacement of the glue seam that the sealant is subjected to has not yet reached the limit of the product.
In the actual construction process, it is unavoidable that the local glue joint is smaller than the design width due to the dimensional deviation or installation deviation of the material processing, as shown in the following figure. In this case, if the same amount of displacement change occurs, the percentage of wide and narrow changes in the relatively small width of the glue joint will increase. If the relatively small width of the glue joint can not withstand the displacement, it will easily occur in local cracking and de-bonding. It is necessary to use high-displacement weatherproof adhesive products. The use of high-displacement products has better sealing weatherability and better guarantees the durability of the curtain wall seal.
Site installation deviation of a project
For the choice of high displacement capability, we can visualize an ordinary person as if he could lift a heavy weight of 25KG. If he is allowed to raise 25KG for a long time, he may be unbearable; but if he can lift a heavy weight of 35KG, he can even Lifting a 50KG weight makes him a lot more relaxed with his 25KG weight. I do not know whether this metaphor will give us a deeper understanding of the choice of displacement ability.
The next issue of “Baiyun Online” will bring you different knowledge about how to choose a weatherproof sealant for curtain wall joints. Stay tuned!