Effective solutions to the problem of swollen aluminum curtain wall sealant

03 / 03 / 2021

Effective solutions to the problem of swollen aluminum curtain wall sealant
With unique texture and various colors, aluminum curtain wall can be designed as a lot of shapes and perfectly combine with glass, stone and other curtain wall materials. Besides, the weight of aluminum curtain wall is light, only accounted for one fifth of marble curtain wall and one third of glass curtain wall, it greatly reduces the load of construction structure and foundation. Also, with low maintenance cost, it is cost-effective and widely used in all kinds of large buildings. 
Weatherproofing silicone sealant is required to seal the joint of curtain wall. But what makes most owners concerned is the swollen sealant joint even if premium weatherproofing sealant has been chosen, which extremely influence the appearance of curtain wall. So here is the question: why is always aluminum curtain wall ‘injured’?

Usually, the swollen aluminum curtain wall appears in winter and spring, it also occurs in summer when it comes to northwest. The cause of swollen sealant joint is the cold drawn and hot pressed because of large deformation of sealant joint before absolute curing. Aluminum plate shrinks and sealant joint widens
when temperature drops at night, sealant is stretched, curing speed of sealant is lower and hasn’t become elasticity at this time. When temperature rises during the day, aluminum plate expands, sealant joint narrows, sealant is compressed, curing process speeds up at this time. Therefore, 
compressed and deformed sealant becomes swollen after curing.

The specific heat capacity of aluminum is only 0.88 × 103J / (kg·℃), while the coefficient of thermal expansion is about 23 × 10-6 M / ℃, which is about three times that of glass. Therefore, aluminum plate is more evidently affected by temperature differences, and deformation caused by thermal expansion and contraction is larger. So, it is always aluminum curtain wall ‘injured’.


Otherwise, it is also influenced by the size of aluminum panel, the orientation of curtain wall, construction time and other factors. Usually, if the aluminum panel is large, curtain wall faces sun and construction is in the morning and evening, weatherproofing sealant has a high probability to become swollen.

As for the swollen weatherproofing sealant of aluminum curtain wall when the temperature difference is large between day and night, there are some suggestions:

1.Choose quick-dry product and construct with high temperature. At this time, the sealant joint is narrow and curing speed is fast, it is not easy to swollen by compression overnight. There is a quick-dry product of antas-193
specially designed for construction of curtain wall in low temperature. It can efficiently solve these problems that joint of weatherproofing sealant becomes bubbling and swollen, and exhibits excellent adhesion to most building materials. Its movement capacity reaches 25%, and it can still maintain performance for normal shear deformation of curtain wall. With the temperature range from 5℃ to 45℃, it exhibits good extrudability and thixotropy.

2.Construction in two times is suggested if sealant joint is deep. The thickness of sealant should be controlled at half the depth of gap while first construction. The second construction should be done in the next day (specific time depends on the degree of sealant curing).

The first sealant will form maintain certain strength after curing, which will reduce the movement caused by thermal expansion and contraction, so the second sealant is not easy to swollen. Even if the surface of first sealant swollen, it will not affect the appearance after covering by second sealant.

It should be noted that the surface of first sealant should be clean and non-dusting while applying the second sealant, otherwise the two sealants can’t be efficiently bonded.
Guangzhou Jointas Chemical Co., Ltd provide epoxy grout sealant,acrylic sealant,exterior sealant,joint sealant compound,potting silicone.You can browse related products and initiate consultations on our website.