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In energy-saving building doors, windows, and curtain walls, the most widely used energy-saving glass is hollow glass. The hollow glass is composed of two or more pieces of glass, separated by an aluminum spacer frame with a desiccant in the middle, and sealed with a sealant on the periphery. The durability and reliability of insulating glass mainly depend on the health and integrity of the edge sealing unit. Once the sealing unit fails, it will not only affect the energy-saving effect of the insulating glass but also bring hidden dangers to the safety of the use of the insulating glass.

The side sealing unit of the insulating glass is composed of the first sealant and the second sealant. The first sealant is butyl rubber, which together with the aluminum spacer frame strip plays the role of isolating moisture; the second sealant Silicone glue or polysulfide glue is mostly used to assume the role of structural bonding of the edge of the insulating glass. At present, researchers generally pay more attention to the influence of material properties, construction technology, and airtightness in the manufacturing process of insulating glass on the performance of the insulating glass sealing unit, that is, the quality of the insulating glass itself. However, it ignores the adverse effects on the performance of the insulating glass sealing unit due to environmental temperature changes during the application of insulating glass.

The side sealing unit of the insulating glass 1

The side sealing unit of the insulating glass 1

During the service of insulating glass, due to the cyclic effects of environmental temperature changes, indoor and outdoor temperature differences, etc., its edge sealing unit will produce a certain expansion and dislocation deformation. If the deformation is too large, the first sealant will be extruded. , Resulting in insufficient width and thickness of the first sealant, and even degumming or breaking of the glue, which seriously affects the performance and service life of the insulating glass, and even causes the complete failure of the insulating glass. In actual curtain wall projects, it is very common that the first sealant of insulating glass is squeezed out, causing the first sealant to break and the aluminum frame strips to be exposed. This situation is not caused by the quality of the insulating glass itself, but by the effect of environmental temperature changes. In addition, as the size of the insulating glass continues to increase, the dislocation and deformation of the edge of the insulating glass caused by the environmental temperature are also increasing, and the impact on the failure of the insulating glass sealing unit is also increasing.

Deformation of the insulating glass sealing unit caused by the temperature difference between the inner and outer sheets of the insulating glass

In the application process of insulating glass, it is bound to be affected by the temperature difference between indoor and outdoor. In the cold winter in the north, the temperature difference between indoor and outdoor can even reach more than 60℃. The temperature difference between the inner and outer glass sheets of the hollow glass caused by the temperature difference between the indoor and the outside leads to a significant difference in expansion and deformation of the inner and outer glass sheets, which in turn causes stress and deformation of the insulating glass sealing unit: the lower temperature side of the glass shrinks, while the higher temperature One side of the glass is elongated, and such edge dislocation and deformation will cause the first sealant at the edge of the insulating glass to be dislocated and squeezed out.In this case, the amount of dislocation deformation of the insulating glass edge sealing unit decreases with the increase of the width of the second sealant glue and increases with the increase of the glue thickness (thickness of the hollow layer). 

However, since the shear modulus of the structural glue itself is several orders of magnitude smaller than the elastic modulus of glass, the restraint of the two-layer sealing structural glue on the glass deformation is relatively limited. The difference in the deformation of the two glass sheets is caused by the temperature difference between the inner and outer sheets of the insulating glass It plays a decisive role in the displacement and deformation of the edge sealing unit of the insulating glass. The displacement deformation of the insulating glass sealing unit is basically linear with its long side size. Therefore, for the ultra-large insulating glass structure (currently, the maximum side length of insulating glass products exceeds 15m), the edge displacement deformation of the insulating glass is relatively large. More attention should be paid to the influence of dislocation and deformation of the first sealant.

The side sealing unit of the insulating glass 2

The side sealing unit of the insulating glass 2

Deformation of insulating glass sealing unit under an environmental temperature difference

The airtight gas in the hollow layer of insulating glass will produce a "breathing" effect under the action of environmental temperature changes. When the temperature of the insulating glass is lower than the production environment temperature, the hollow glass will be concave, causing the first sealant to overflow; hollow glass When the use environment temperature is higher than the production environment temperature, the hollow glass will be convex. Once the convex deformation of the glass is too large, the first sealant will be pulled apart and degummed. The reciprocating cycle of the above situation, especially the combination of the ambient temperature and the temperature difference between the inner and outer sheets, accelerates the failure of the first sealant on the edge of the insulating glass.

Under the action of environmental temperature changes, the internal cavity of the hollow glass produces a pressure difference with the outside air, and the glass is bent into a spherical surface under the action of the uniform pressure difference. In this case, the edge deformation of the large-size insulating glass is smaller than that of the small size, and the maximum deformation of the edge sealing unit is only micron-level.   

Summary  

It can be seen that in addition to the quality of the insulating glass itself, the ambient temperature also has an important influence on the durability and reliability of the insulating glass performance. The effect of the temperature difference between the inner and outer sheets on the insulating glass is mainly the dislocation and deformation of the edge sealing unit. Dislocation deformation increases as the size of the hollow glass increases and is approximately linear. Therefore, the edge distortion of large-size hollow glass has a greater impact on its performance. However, the deformation of the first sealant at the edge caused by the "breathing" effect of the insulating glass under ambient temperature is only in the micron range and decreases with the increase of the size of the insulating glass.

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