How to use silicone structural sealant in winter?

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

1) When the temperature is too low, the wettability of the sealant and the substrate surface is reduced, and there may be imperceptible fog or frost on the substrate surface, affecting the bond between the sealant and the substrate.

2) Under low temperature and low humidity conditions, the curing speed and bonding speed of silicone sealant are slower than normal, which will lead to longer maintenance time and affect the construction.

So what do we need to pay attention to to avoid the above problems?

At present,the building silicone structural sealant used in the construction of curtain wall engineering is classified into two types by component:one is a single-component silicone structural sealant,and the other is a two-component silicone structural sealant.

The one-component silicone structural sealant reacts with water in the air to cure,gradually curing from the surface of the adhesive,and the deeper the adhesive crack,the longer it takes to fully cure.Due to the reaction curing of component A (containing a small amoount of water),component B and water in the air,the surface and the interioe are cured at the same time,and the surface curing speed is greater than the internal curing speed(affected by the size of the glue joint and the sealing condition).

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

1. The construction environment should be guaranteed

During winter construction,heating measures should be taken to ensure that the construction temperature is higher than 10 ℃;If the user has special circumstances and needs to be executed in a low temperature environment(such as the ambient temperature is sightly below 10℃),it is recommended to carry out a small area gluring test before use,and the carry out a peel bonding test to confirm that the sealant is cured and bonded well, and to extend the curing time appropriately depending on the situation. When necessary, it can be considered to use xylene cleaning and primer to speed up the bonding speed and reduce the risk of poor bonding due to low ambient temperature.

2. The sizing process should be careful to prevent poor bonding

1) Before construction, the adhesion test should be carried out in advance, and the construction method recommended by the adhesion test should be strictly followed.

2) There are many batches of materials (aluminum, glass, sealant, cleaning agent, primer, etc.) used in the construction process, and it is necessary to pay attention to the differences between different batches. In the production process, the materials entering the factory need to be randomly tested for on-site adhesion. 

3) During the construction process, the method of cleaning or coating the base coating liquid should comply with the construction technology, and clean in strict accordance with the 'secondary rag method'. After the cleaning solvent is volatilized, the base coating liquid should be applied in time; The bottom coating liquid should be thin and uniform, pay attention to the connection of the next process, and it is best to carry out the glue injection construction within half an hour after the bottom coating. 

4) During the gluing process, it should be noted that components A and B are evenly mixed, and within the range of mixing ratio recommended by the manufacturer, which can be confirmed by butterfly test and pull break test respectively. Adequate exhaust should be noted when changing the drum. If the exhaust is not sufficient, the part of the sealant will contain a large number of dense bubbles, which we call 'bubble glue'. The bonding effect of bubble glue and the substrate (aluminum, glass, etc.) is very poor, and the adhesive strip is separated from the substrate by pulling it by hand, and at the same time, it often leaves a black mark on the substrate. 

5) After the production of the site plate, the plate should be moved horizontally to the maintenance area for maintenance. In the process of moving the aluminum frame and the glass are not allowed to misposition, otherwise it will affect the bonding quality of the structural adhesive. 

3. The maintenance environment and maintenance time should ensure that the unit rubber cutting qualified

After the sealant injection is completed, the curing process should be in a clean and ventilated environment, the temperature is maintained at 10-40 ° C, and the humidity is 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 obvious in the single-component structural adhesive: that is, the curing condition of the single-component sealant has a significant relationship with the curing time. In the same environment, the longer the curing time, the higher the curing degree. If necessary, measures can be taken to increase the ambient temperature and humidity. Finally, the cutting test should prevail, and the maintenance time of the finished unit should be fully determined. Only after the finished product has passed the cutting test (see the figure below) can it be installed and transported.