Application of sealant in energy saving field
With the increase of the pace of modernization in China, the development and consumption of energy have received increasing attention. Solving the energy problem is the need to ensure sustainable economic development, but to fundamentally solve energy constraints, we must not only insist on saving, but also innovate, that is, to develop and utilize new technologies and materials, to meet increasing energy-saving requirements, and to improve There are energy-saving effects of curtain wall doors and windows. Therefore, vigorously promoting the use of energy-saving curtain wall doors and windows is a necessary measure to reduce building energy consumption. From this point of view, the development of curtain wall doors and windows should also shift from the original decorative type to the future functional type.
Sealant plays an important role in the application of energy-efficient curtain walls and windows and insulating glass. The sealant is used in the joint seal of the building to seal it, as shown in Figure 1. The various joints on the building are affected by factors such as temperature and external force. The sealant must withstand the change of the joint and the environmental influence (water, light, cold, heat) in the joint without being damaged. The primary properties considered by sealants are elasticity and adhesion, and secondly, the weatherability and strength of the sealant.
The sealing performance of the sealant is described by taking the curtain wall and the insulating glass for the curtain wall as an example: Figure 2 is an assembly view of the curtain wall. It can be seen from Fig. 2 that the sealant is tightly sealed in all places where the inside and outside of the building are connected, and structural glue and weather resistant glue are used. The bond between the insulating glass and the building is structural glue because it acts as a load bearing. It not only binds the glass and the building tightly together for a long time, but also affects external forces such as wind load and gravity load. It can still maintain good bonding and stability; between the two insulating glass is weather-resistant glue, which directly seals the passage between the outside and the building, making the building a closed system and saving energy. The hollow glass at the bottom of Figure 2 is enlarged, see Figure 3 (in section of the insulating glass).
The role of the sealant in the insulating glass is to maintain the gas in the air layer, thereby facilitating the long-term energy-saving effect of the insulating glass and sealing, and the second is to keep the structure of the insulating glass stable and to act as a bonding.
If one of these two functions is not achieved, the energy-saving effect of insulating glass will not be discussed. Insulating glass always faces external water vapor infiltration, wind and rain, sun exposure, ultraviolet radiation, changes in temperature difference of four seasons, etc., as well as external forces such as air pressure and wind load. Various environmental factors work together to make insulating glass face. The more severe conditions, therefore, the sealant must be impervious to water, airtight, radiation-resistant, temperature-resistant, moisture-resistant, etc., while also meeting the requirements of the insulating glass production process.
In order to ensure the quality of the insulating glass, the high-quality sealant is the most basic guarantee for the production of insulating glass with good performance. Special attention is paid to the fact that structural adhesives are essentially different from ordinary sealants. The choice of silicone structural adhesives should be cautious because the substrate is bonded to the main structure and is subjected to wind loads and the weight of the glass. The structural adhesive must have Sufficient strength to withstand these loads. At the same time, the structural adhesive should meet the elastic modulus specified by the standard. The designer needs to calculate the thickness of the structural joint according to the elastic modulus. The low modulus sealant is not suitable for structural adhesive. The effect of low modulus adhesive on wind load or self-weight load There will be large displacements underneath, which is not allowed in glass curtain wall construction. However, the modulus of the structural adhesive should not be too high, because the structural adhesive must be adapted to the deformation of the rubber joint caused by its own weight load, wind load and the like.
1.Butyl sealant common problems
(1) The first butyl insulating glass sealant as the insulating glass and the second silicone or polysulfide insulating glass sealant are directly sealed into one body. Because some manufacturers produce silicone rubber and polysulfide rubber contain a lot of mineral oil or butyl rubber itself contains mineral oil. The produced insulating glass causes butyl flow or rainbow phenomenon when exposed to sunlight or heat.
(2) The glass glue used in the hollow glass frame and the second hollow glass sealant of the insulating glass are in direct contact with the point, and are in indirect contact with the first butyl insulating glass sealant of the insulating glass. If the glass glue contains a lot of mineral oil, it will also cause butyl gum flow or rainbow phenomenon.
(3) The weather-resistant glue used in the curtain wall plate is in contact with the second sealant of the insulating glass, and is in indirect contact with the first butyl rubber of the insulating glass. If the weathering rubber contains a large amount of mineral oil, it will also cause butyl gum flow or rainbow phenomenon. The direct result of these phenomena is the failure of the seal and the inability to save energy.
2. silicone sealant cracking
(1) This phenomenon is also very common. In order to reduce the cost of some low-grade sealants, it is a direct cause to use low-priced, unstable-performance fillers.
(2) Another important reason for the cracking of the sealant is caused by the construction environment.
3. insulating glass fog
In general, good insulating glass design should adopt a double-pass sealing structure, a suitable desiccant, a first sealant with low water vapor transmission rate, a second sealant with excellent shear-stretching tensile strength and continuous corners. Spacer without spacers. Although various high-performance insulating glass designs use many high-tech materials to make the insulating glass have functions such as anti-condensation, noise reduction, thermal resistance and glass bursting, the sealant that plays an important role in the performance and life of the insulating glass is It should be taken seriously at all times.
(1) The sealant used in energy-saving buildings must have water-impermeable, air-tight, radiation-resistant, temperature-resistant, moisture-resistant and other properties to meet the long-term life expectancy of energy saving and sealing.
(2) In order to ensure the quality of the seal, the quality of the sealed collagen material must be controlled to ensure the stability of the formulation. It is absolutely impossible to add an auxiliary agent which seriously affects the compatibility of the sealant and the substrate for the purpose of reducing the cost.
(3) The problems of cracking, flowing, and fogging of the sealant that occur during use must be taken to overcome the problem of the quality of the curtain wall.
(4) After comparison test with similar foreign products, including long-term exposure to natural conditions and accelerated accelerated aging test, the silicone structural adhesive produced by the company has excellent durability and is equivalent to the performance of foreign high-quality products.
(5) Developed a variety of new products to meet the needs of sustainable development of energy-efficient buildings, such as ultra-high performance and high elongation silicone rubber, transparent silicone rubber, transparent and white butyl rubber, fire retardant sealant, etc. It greatly enriches the variety of building sealing materials to meet the different needs of various styles of architecture.