What issues should we pay attention to when using sealant in winter?

In winter, when the ambient temperature is very low, the following problems may occur:

1) When the temperature is too low, the humidity on the surface of the sealant and the base material decreases, and imperceptible mist or frost may appear on the surface of the base material, which affects the bonding of the sealant and the base material.

2) Under low temperature and low humidity conditions, the curing speed and bonding speed of silicone sealant are slower than normal conditions, which will lead to longer curing time and affect construction. So what do we need to pay attention to to avoid the above problems?

Currently, the architectural silicone structural sealants used in curtain wall engineering construction are divided into two categories according to their components: one is single-component silicone structural sealant, and the other is two-component silicone structural sealant.

The one-component silicone structural sealant reacts with water in the air to solidify, and gradually solidifies from the surface of the adhesive. The deeper the sealant seam, the longer it takes for complete curing. Due to component A (containing a small amount of water), component B and water in the air, the surface and interior are cured at the same time, and the surface curing speed is greater than the internal curing speed (affected by the sealant gap size and internal curing speed) sealing conditions.

The curing speed of one-component silicone structural sealant is slower than that of two-component, and the speed is not adjustable and is easily affected by ambient temperature and humidity. Generally speaking, the lower the temperature, the slower the reaction; the lower the humidity, the slower the reaction.

1. The construction environment must be guaranteed

During winter construction, heating measures should be taken to ensure that the construction temperature is higher than 10°C; if the user has special circumstances and needs to construct in a low-temperature environment (such as the ambient temperature is slightly lower than 10°C), it is recommended to conduct a small area sealant test before use. , and conduct a peel adhesion test to confirm that the sealant is cured and adhered well, and the curing time is appropriately extended according to the situation. If necessary, consider using a xylene wash and primer to speed up bonding and reduce the risk of poor bonding due to low ambient temperatures.

2. Be careful during the gluing process to prevent poor adhesion.

1) Adhesion testing should be carried out in advance before construction, and the construction methods recommended by the adhesion testing should be strictly followed.

2) There are many batches of materials (aluminum, glass, sealants, cleaning agents, primers, etc.) used in the construction process, so attention should be paid to the differences between different batches. During the production process, materials entering the factory need to be randomly tested for on-site adhesion.

3) During the construction process, the method of cleaning or applying the primer liquid should comply with the construction process, and clean in strict accordance with the "secondary rag method". After the cleaning solvent evaporates, the primer should be applied in time; the primer should be thin and even, and pay attention to the connection with the next process. It is best to carry out the sealant injection construction within half an hour after the primer.

4) During the gluing process, attention should be paid to mixing components A and B evenly, and within the mixing ratio recommended by the manufacturer, to confirm through butterfly tests and pull-off tests respectively. When replacing the drum, pay attention to adequate exhaust. If the exhaust is insufficient, the sealant part will contain a large number of dense bubbles, which we call "bubble sealant". The bonding effect between bubble sealant and the base material (aluminum, glass, etc.) is very poor. When the adhesive strip is pulled by hand, it will be separated from the base material, and at the same time, black marks will often be left on the base material. matrix.

5) After the on-site plate production is completed, the plates should be moved horizontally to the maintenance area for repair. During the movement, the aluminum frame and the glass are not allowed to be misaligned, otherwise it will affect the bonding quality of the structural adhesive.

3. The maintenance environment and maintenance time should ensure that the unit’s sealant cutting is qualified.

After the sealant injection is completed, the curing process should be carried out in a clean and ventilated environment, with the temperature maintained at 10-40°C and the humidity maintained at 50-90%. When the temperature and humidity of the maintenance environment are low, the maintenance time should be appropriately extended. This situation is particularly obvious in one-component structural adhesives: that is, the curing conditions of one-component sealants have a significant relationship with the curing time. Under the same environment, the longer the curing time, the higher the degree of curing. If necessary, measures can be taken to increase the ambient temperature and humidity. Finally, the cutting test will be used to fully determine the maintenance time of the finished unit.