As winter comes, the temperature drops, the big temperature difference between day and night, and the air also become dry. During the silicone structural sealant construction, the sealant curing speed and bonding speed will be affected by the low temperature of the environment, low humidity.

1 Slow curing speed of silicone sealant

The first problem brought by the sudden drop in ambient temperature is the slow curing. Silicone structural sealant curing process is a chemical reaction process, the temperature and humidity of the environment have a certain impact on its curing speed. For one-component silicone structural sealant, the higher the temperature and humidity, the faster the curing speed will be. In winter, the temperature drops, along with low humidity, the curing reaction of the structural sealant is affected, and thus the structural sealant curing slow. In general, when the temperature is lower than 15 ℃, the phenomenon of structural sealant curing slower is more obvious.

Solution: If the user wants to construct in a low-temperature environment, it is recommended that a small-area glue test be conducted before use, and a peel bonding test, to confirm that the structural sealant can be cured, good bonding, no problems with the appearance before using a large area. However, it is not recommended to construct a structural sealant when the use of ambient temperature is lower than 4℃. If the construction is in the factory, you can consider increasing the temperature and humidity of the environment used for structural sealant.

2 Structural silicone sealant bonding problems

With the reduction of temperature and humidity, accompanied with curing slowly is bonding problems between structural silicone sealants and substrates. The general requirements of the environment for silicone structural sealant: temperature 4 ℃ ~ 40 ℃, relative humidity 40% ~ 80% of the clean environment. Beyond the above minimum temperature requirements, the bonding speed slows down and the time to fully bond with the substrate is extended. At the same time, the temperature is too low, the adhesive and the substrate surface wettability is reduced, and there may be imperceptible fog or frost on the surface of the substrate, which affects the bonding of the structural sealant and the substrate.

The solution: when the temperature is lower than the minimum construction temperature of structural silicone sealant 4 ℃, do a bonding test to confirm good bonding before construction. The factory environment applying can also by increasing the temperature and humidity of the environment to speed up the curing of structural sealant, and also need to properly extend the maintenance time.

3 Structural silicone sealant thickening

As the temperature decreases, the structural silicone sealant will gradually thicken and become less liquid. For a two-component structural sealant, structural sealant thickening will make the glue machine pressure increase, structural sealant extrusion becomes smaller. For a one-component structural sealant, the structural sealant thickens, the pressure of the glue gun to extrude the structural sealant increases, and the manual operation may feel time-consuming and laborious.

Solution: If there is no impact on the construction efficiency, the low-temperature thickening is a normal phenomenon and no improvement measures are needed. If there is an impact on the construction efficiency, you can consider increasing the temperature of the structural silicone sealant or using some auxiliary heating measures, such as storing the structural sealant in advance in a warm room or air-conditioned room and installing heating in the glue shop to improve the temperature of the glue environment. In addition, you can choose the appropriate glue tools, such as a thrust manual glue gun or pneumatic glue gun, electric glue gun, etc.

4 Weatherproof silicone sealant bulging - uneven appearance

When in a low-temperature environment, weather silicone sealant prone to drumming phenomenon, weather silicone sealant curing speed becomes slower, its surface curing enough depth of time required will be longer, if the width of the rubber seam changes (which is usually due to thermal expansion and contraction of the panel) is larger, the surface of the rubber seam will be affected, the appearance of uneven drumming phenomenon.

Solution: If the relative deformation of the glue joint is too large due to low humidity or temperature difference, size of the glue joint, etc., it is recommended to use one or more of the following ways for construction. 

1. The use of appropriate shading measures, such as the use of dust nets and other shading scaffolding, so that the panel is not directly exposed to sunlight exposure, reduce the temperature of the panel, reduce the temperature difference caused by the deformation of the joints. 
2. Try to arrange construction around noon, avoid morning and evening construction. 
3. The use of secondary glue method (i.e., the first apply glue if there is a depressed glue seam, can be cured for 2 ~ 3 days, with elasticity, and then make up a layer of glue on its surface).

Other precautions,

Ⅰ: How to store the sealant in winter?

The best storage temperature of silicone weatherproof sealant is: 0~27℃. If possible, it can be placed in an air-conditioned room with constant temperature and humidity. In addition, the construction temperature of the weather sealant should not be lower than 4℃ or more than 40℃.

Ⅱ: Can silicone sealant be used in the temperature be lower than 4 degrees and relative humidity 35%?

  It is not recommended for the user to construct the glue, because,

1. the temperature is too low, the adhesive and the substrate surface wettability is reduced, and there may be imperceptible fog or frost on the surface of the substrate, affecting the adhesion of the sealant and the substrate. 
2. In low temperatures, the curing speed of silicone sealant is slower than normal. The sealant has not yet cured before encountering changes in the seam, which can easily cause the surface of the sealant to bulge or crack, affecting the appearance of the sealant.