Curing Characteristics of Sealant
Curing characteristics of one-component sealant: It absorbs moisture from the air and gradually cures from the surface inward. The surface dries faster, and the deeper layers cure slower. The deeper the bonding seam, the longer it takes to fully cure. The curing speed is easily affected by ambient temperature and humidity. When the ambient temperature is low, both the surface drying time and the deep curing speed will slow down. When the ambient humidity is low, the deep curing speed will slow down.
Curing characteristics of two-component sealant: It cures through the reaction of component A and component B, curing the surface and interior simultaneously. The full curing time is hardly affected by the size of the bonding joint. The curing speed is less affected by ambient humidity and more affected by temperature. The lower the temperature, the slower the curing speed. At the same time, the curing speed can also be adjusted by the amount of component B. The smaller the amount of component B, the slower the curing speed; the larger the amount of component B, the faster the curing speed. However, the adjustment range of the amount of component B should be strictly controlled within ±20% of the specified amount. If the amount of component B is too high, the cured sealant will become brittle and lose its elasticity; if the amount of component B is too low, the sealant will not fully cure.

Construction Suggestions: During the construction of silicone weather-resistant sealant, users should follow the usage environment requirements recommended by the silicone weather-resistant sealant manufacturer; the usage environment requirements for silicone weather-resistant sealant products are: clean environment, temperature 4℃～40℃, relative humidity 40%～80%. It is recommended that users do not apply sealant in environments outside the above temperature and humidity requirements; outdoor construction cannot be carried out in rainy or snowy weather. It should be noted that the requirements for the construction environment may vary among different manufacturers, and this should be confirmed before construction.
Common Problems in Winter Construction
In winter construction, low temperature and low humidity will affect the curing and bonding speed of silicone sealant, which may cause problems during construction. Common problems include:
1. Slow sealant curing
The primary problem caused by a sudden drop in ambient temperature is that the curing process feels slow during use. The curing process of silicone sealant is a chemical reaction process, and changes in ambient temperature have a significant impact on the curing speed; the higher the temperature, the faster the curing speed; the lower the temperature, the slower the curing speed. Generally speaking, after the winter temperature drops below 15℃, whether it is a one-component sealant or a two-component sealant, its surface drying time and deep curing speed will slow down significantly. At low temperatures, the curing time of silicone adhesive needs to be extended. In summer, it only takes one or two days to dry, while in winter it may take three days or even longer.
In addition, many places have dry and cold weather in winter, with low temperatures and low relative humidity. The deep curing of one-component silicone sealant requires moisture from the air to penetrate into the sealant, so humidity also has a significant impact on one-component silicone sealant. When there is less moisture in the air and the relative humidity is below 40%, the deep curing of one-component silicone adhesive will slow down significantly.

2. Poor sealant adhesion
As the temperature decreases, the bonding activity between the silicone adhesive and the substrate interface decreases, and a longer curing time is required to achieve satisfactory bonding results.
When the temperature is too low, the sealant will become more viscous, and the wettability on the substrate surface will decrease, which is not conducive to the spreading and penetration of the sealant on the substrate surface, and will also affect the bonding between the sealant and the substrate.
When the temperature is too low, there may be imperceptible fog or frost on the substrate surface, which will also affect the bonding between the sealant and the substrate. Before applying the sealant, it is necessary to fully confirm that the substrate surface is dry before construction.
3. Sealant thickening
Polymer materials all have the characteristic of viscosity temperature coefficient. As the temperature decreases, the sealant will gradually thicken and its fluidity will decrease. For two-component sealants, sealant thickening will increase the pressure of the caulking gun and reduce the extrusion amount of the sealant. For one-component sealants, sealant thickening will increase the pressure of the caulking gun extruding the sealant, and manual operation may feel time-consuming and laborious. If it does not affect the construction efficiency, low-temperature thickening is a normal phenomenon.

4. Weather-resistant sealant bubbling and wrinkling—uneven appearance
Under low-temperature and low-humidity conditions in winter, the curing speed of silicone sealant is much slower than at normal temperature, and there is often a large diurnal temperature difference. Taking the common construction of aluminum curtain walls with high linear expansion coefficient and significant deformation with temperature changes as an example, the curing speed is reduced, and the time required for the surface to cure to a sufficient depth will be longer. When the sealant has not cured to a sufficient depth, if the joint width changes, such as excessive temperature difference, thermal expansion and contraction of the panel, manual movement or handling causing the plate to be squeezed or stretched, etc., the joint surface will be affected, resulting in bubbling or wrinkling and other uneven appearance phenomena. After final curing, these uneven joints are solid rather than hollow and will not affect the sealing performance of the weather-resistant sealant, only the flatness of the joint appearance.

Suggestions for Using Sealant in Winter
1. Choose an adhesive with a relatively fast curing speed.
2. Improve construction conditions, such as using air conditioners, humidifiers, etc., to increase the ambient temperature and humidity, and improve the curing speed of silicone adhesive in factories with conditions.
3. When constructing two-component sealant, the mixing ratio should be adjusted appropriately. During injection, attention should be paid to the uniform mixing of components A and B, and within the mixing ratio recommended by the manufacturer. This can be confirmed by the butterfly test and tensile test respectively.
After the on-site panel is made, attention should be paid to the curing temperature, humidity, and curing time. When the curing temperature and humidity are low, the curing time may need to be extended. The final step should fully determine the curing time of the finished single component based on the rubber cutting test.
5. If the relative deformation of the adhesive joint is too large due to low humidity or temperature difference, adhesive joint size, etc., it is recommended to use one or more of the following methods for construction:
a) On cloudy days, the diurnal temperature difference is small, and the deformation of the adhesive seam is small, which can reduce the bubbling and wrinkling phenomenon on the surface of the adhesive strip.
b) Take appropriate shading measures, such as using dust nets to cover the scaffolding, to prevent the panels from being directly exposed to sunlight, reduce the panel temperature, and minimize seam deformation caused by temperature differences.
c) Do not work on surfaces directly exposed to sunlight for the time being.
d) A secondary gluing method can be used (i.e., first glue the concave glue seam, let it cure for 2-3 days to become an elastomer, and then apply another layer of glue to its surface).
6. If construction must be carried out under low-temperature conditions, it is recommended to conduct small-scale bonding tests and peel bonding tests before use to confirm that the sealant can cure, bond well, and have no appearance problems before large-scale use.
a) When the temperature is lower than the minimum construction temperature of the sealant by 10℃, the bonding performance of the sealant adhesive substrate should be tested in the actual low-temperature construction environment, and the construction process should strictly follow the recommended method of bonding performance testing. Confirm good bonding before construction.
b) Many batches of materials (aluminum, glass, sealant, cleaning agent, primer, etc.) were used during construction, and it should be noted that there may be differences between different batches. During production, random on-site bonding tests are required for each batch of materials entering the factory.
c) If a primer is required, during construction, the cleaning or coating method should comply with the construction process. After the cleaning solvent evaporates, the primer should be applied promptly; the primer should be applied thinly and evenly, paying attention to the connection with the next process. It is best to apply the glue within half an hour after the primer has dried.