1. Interface design does not match the sealant displacement capability.
It is often found that the sealant cracks when it is used at the interface of the aluminum curtain wall, especially during the seasonal change, the temperature difference between day and night is especially large, and the excessive stretching of the sealant is caused by the shrinkage of the plate when the temperature drops. This is mainly due to the displacement capacity of sealant can not meet the actual requirements.
2. Improper choice of sealant.
At present, there are a lot of sealant products for weather and waterproof on the market: polyurethane sealant, polysulfide sealant and silicone sealant. In engineering cases, many people do not pay attention to the difference of several kinds of sealants, and arbitrarily choose to use in the aluminum curtain wall, often appear sealant surface cracking, pulverization phenomenon.
3. Poor bonding.
The problem with aluminum curtain walls is the poor bonding between sealants and aluminum sheets. Because the surface treatment methods of aluminum plate include anodic alumina, fluorocarbon spraying and powder spraying, different treatment methods and different manufacturers'treatment processes will affect the surface structure and performance of aluminum plate, thus affecting the adhesion of sealant.
4, other construction operations improper
In order to avoid scratches in the process of processing and transportation, a PE protective film is usually coated on the surface of aluminum sheet units. Therefore, after the aluminum plate is installed, the PE protective film needs to be cleaned before sizing.
5. The surface of the sealant is plucked up.
The thermal expansion coefficient of aluminium sheet is large. When the temperature difference is large, the thermal expansion and cold shrinkage of aluminium sheet will easily lead to bulging on the surface of uncured sealant, especially on the transverse joints. Drum phenomenon occurs because the inside of the sealant is solid, will not affect the sealing effect, mainly for this phenomenon, can take two sizing solution, or in a relatively constant ambient temperature period of sizing operation.
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