What is the reason for "bulging" of silicone sealant?

1.Displacement capacity of sealant: 

For a specific curtain wall project, since the plate size, linear expansion coefficient of the panel material, annual temperature change of the curtain wall, etc. are all fixed values, the minimum displacement capacity required by the sealant can be calculated based on the set glue joint width. When the joint is narrow, it is necessary to select a sealant with a higher displacement capacity to meet the joint deformation requirements.

2.Sealant curing speed:

At present, most sealants used in domestic building joints are neutral silicone sealants, which can be divided into deoxime type and dealcohol type according to the curing category. The curing speed of deoxime type silicone sealant is faster than that of dealcohol type silicone sealant. In a construction environment with low temperature, large temperature difference and low relative humidity, the use of deoxime type silicone sealant can solve most of the "bulging" problems. The faster the sealant cures, the stronger the ability of the sealant to withstand joint deformation during curing; the slower the curing speed, and the greater the displacement deformation of the joint, the more likely the sealant joint will "bulge".

3.Temperature and humidity of the construction site environment: 

Single-component silicone weather-resistant sealant for construction can only cure after reacting with moisture in the air, so the temperature and humidity of the construction environment have a certain impact on its curing speed. Generally speaking, when the temperature and humidity are high, the reaction and curing speed is fast; when the temperature and humidity are low, the curing reaction speed is slow, and the glue joint is prone to "bulging".

4.Panel material: 

Aluminum plate has a larger thermal expansion coefficient among common panel materials. Its linear expansion coefficient is 2 to 3 times that of glass. Therefore, the thermal expansion and contraction deformation of aluminum plate of the same size is greater than that of glass. It is more likely to cause large thermal displacement and "bulging" due to the temperature difference between day and night. The larger the size of the aluminum plate, the greater the deformation caused by the temperature difference.