Discussion on Adhesion of Silicone Sealant to Insulating Glass

Abstract: This article starts from the actual use environment of insulating glass, and investigates the adhesion of silicone sealants from different manufacturers to uncoated float glass and offline Low-E glass. When comparing different aging conditions, it is found that the adhesion of silicone sealants to uncoated float glass and offline Low-E glass is most affected by water and UV aging treatment, and the water and UV adhesion of silicone sealants from different manufacturers vary same. Under the circumstance that it is difficult to achieve the same level of cleanliness as the surface of uncoated float glass on the surface of the Low-E glass that has been removed from the film, choosing a high-quality silicone sealant with good water resistance and UV adhesion can achieve good bonding to the Low-E glass that has been removed from the film. sealing effect.

Keywords: silicone sealant; insulating glass; water UV bonding

1. Introduction

The energy problem is the primary problem of today's world economic development, and energy conservation is an inevitable requirement to achieve sustainable development. Therefore, building energy conservation has also received increasing attention. Glass doors and windows are the weakest energy-saving parts of the four major components of the building envelope, and insulating glass is one of the effective ways to slow down its energy dissipation. Low-E glass can not only meet people's aesthetic needs for buildings, but also solve the problems of heat control, cooling cost and internal sunlight projection comfort balance in buildings. It has become an increasingly important part of the field of building energy conservation. Low-E insulating glass is in the middle of two or more pieces of low-emissivity coated glass, the glass is separated by aluminum, frame or tape injected with desiccant, and the surrounding is sealed with glue, so that the intermediate cavity (the entry "cavity") Body "provided by industry Google) always keep dry (entry "dry" provided by Google) gas, its unique space structure can block the channel of heat conduction, thereby effectively reducing its heat transfer coefficient, with energy saving, sound insulation, environmental protection function Glassware (entry "glassware" courtesy of Google). Jinan LIJIANG Glass analyzed the failure causes of insulating glass, and pointed out that sealant is one of the factors affecting the failure of insulating glass.

In the global insulating glass market, the sealing process of insulating glass can be divided into three types of sealing, double sealing and single sealing, the latter two types of sealing are more common. The most common room temperature cure sealants use a two-pass sealing process. The inner channel (or one channel) sealant of the double-channel seal is mainly made of thermoplastic polyisobutylene sealant, and its main function is to reduce the permeability of water vapor and edges. The outer (or secondary) sealants mainly include polysulfide sealants (PS) and silicone sealants (SD), which mainly play the role of bonding and sealing. Silicone sealant has good bonding performance and UV aging resistance, and can be applied to all insulating glass, so it is widely recognized by the market. This article mainly discusses the influencing factors of the adhesiveness of silicone sealant for insulating glass.

2. Experimental part

2.1 Experimental materials and instruments

Several uncoated float glass and LOW-E glass are commercially available;

There are five kinds of silicone structural adhesives on the market (S1, S2, S3, S4, S5), of which S1 is the sealant for Sibao LOW-E film removal glass, S2 is a foreign brand silicone sealant, S3, S4, S5 is a silicone sealant of different brands made in China;

Three kinds of film removal wheels (L1, L2, L3) are commercially available;

Universal electronic material tensile testing machine: AGS-J (5 kN, precision 0.5), Shimadzu Instrument (Suzhou) Co., Ltd.;

UV light aging tester: BR-PV-UVT, Shanghai Borui Scientific Instrument Co., Ltd.

2.2 Experimental test

Use the silicone structural sealant according to the usage method provided in the product instruction manual, refer to the industry standard "Silicone Structural Sealant for Insulating Glass", and use 50mm*50mm*6mm Low-E glass or uncoated float glass as the adhesive. After 14 days of curing under the standard conditions, they were treated in a 45°C water UV box for 300h (UV wavelength). 340nm), immersed in water for 300h, treated in a UV box for 300h (ultraviolet wavelength 340nm), and then conducted a tensile bond test.

^{Figure 1 Test module for UV bonding of silicone structural adhesive to Low-E glass water}

3. Results and discussion

3.1 Adhesion of silicone sealant to uncoated glass

In this experiment, the effects of silicone sealants produced by different manufacturers on uncoated float glass were investigated in normal state, immersion in water for 300h, in UV box for 300h (UV wavelength 340nm), and 45°C water UV box for 300h (UV wavelength 340nm). ) and other conditions, the results are shown in Table 1.

It can be seen from Table 1 that silicone sealants of different manufacturers have certain differences in the adhesion and tensile bonding strength of uncoated glass. Insulating glass manufacturers should choose silicone sealants with better adhesion. At the same time, sealants with different tensile bond strengths are selected according to the design requirements. When comparing the adhesion of silicone sealants to glass from different manufacturers, it can be found that silicone sealants show good adhesion to uncoated glass, but S3, S4, and S5 glue samples appear to have a certain degree of adhesion after being treated with water and UV at 45°C. The adhesion failure of the S5 glue sample is 30%. Judging from the tensile bond strength of silicone sealants treated under different conditions, the 45 ℃ water UV treatment condition has the greatest influence on the tensile bond strength of the colloid, and the tensile bond strength of S4 and S5 decreases the most. Insulating glass will be exposed to sunlight, rain or moisture for a long time in actual use, so it is necessary to study the water UV adhesion of silicone sealants, and water-resistant UV adhesion should also be used in the production of insulating glass. Better silicone sealant.

3.2 Adhesion of silicone sealant to offline LOW-E glass

Because Low-E insulating glass has excellent energy-saving effect compared with ordinary insulating glass, it is more and more popular in the market. In this experiment, S1, S2 and S3, which have better UV adhesion to uncoated glass water, were investigated for off-line Low-E glass. The adhesion of glass, the test results under different treatment conditions are shown in Table 2.

It can be seen from Table 2 that the S1 and S2 silicone sealants are easy to peel off the Low-E film from the glass surface during the test of the H-type specimen due to the high tensile bond strength of the colloid, especially at 45°C water UV Under the conditions, the Low-E film was peeled off in the three samples prepared by silicone adhesive. The production process of offline Low-E glass is usually to deposit a large number of atomic (or molecular) film layers on the surface of the glass substrate by vacuum magnetron sputtering. The film formed by the process is a soft film, and the wear resistance, chemical stability (the entry "chemical stability" is provided by Google), and thermal stability of the film are poor [3]. When it is high, it is easy for the Low-E film to be peeled off by the sealant. Figure 2 shows the Low-E film peeled off by the S1 silicone sealant.

^{Figure 2 The peeling of the UV-stretch adhesive film of Low-E glass water}

From Figure 2, it can be seen that the S1 silicone glue adheres well to the Low-E glass de-filmed part, while the LOW-E film of the un-de-filmed part is removed from the glass panel by the silicone glue S1 (the entry "glass panel" is provided by Google provided) on the torn case. The peeling of the film layer will cause the bonding and sealing of the insulating glass to fail, indicating that in the production process of the Low-E insulating glass, it is necessary to remove the film on the edge that needs to be sealed and bonded. Most Low-E insulating glass manufacturers have carried out film removal treatment on the edge. Therefore, this paper investigates the water UV adhesion of silicone sealant to Low-E film removal glass.

3.3 Investigation of water UV adhesion of silicone sealant to Low-E glass

3.3.1 Influence of film removal method on adhesion

In this experiment, the water UV adhesion of different silicone sealants to LOW-E glass with different degrees of film removal was investigated, and the results are shown in Table 3.

^{Figure 3 S1 test results of UV bonding of Low-E glass water for one-time film removal}

^{Figure 4 S3 test results of UV bonding of LOW-E glass water for one-time film removal}

It can be seen from Table 3 that the silicone sealant has good water-UV adhesion to uncoated float glass, but relatively poor water-UV adhesion to Low-E glass or de-filmed Low-E glass, especially The Low-E film is also peeled off on the unremoved glass, indicating that the existence of the Low-E film is the main factor affecting the adhesion of the silicone sealant to the Low-E glass. Secondly, the adhesiveness of the silicone sealant to the Low-E glass that has been removed twice is significantly better than that of the Low-E glass that has been removed once. Manually remove the Low-E glass. For the same Low-E glass and film removal equipment, the removal effect of the two-time film removal process on the Low-E film is significantly better than that of the one-time film removal process, and the film removal effect of the automatic film removal equipment is significantly better than that of manual film removal. , it can be seen that the film removal effect on the surface of the film removal glass will affect the adhesion of the silicone sealant to the film removal Low-E glass. When the Low-E glass with manual film removal and the Low-E glass with one-time film removal by automatic Low-E Edge Deleting Machine are used as the bonding substrates, it can be clearly seen that the water UV adhesion of different silicone sealants to the film removal glass is obvious. The adhesion of S2 is better than that of S3, and the adhesion of S3 is obviously better than that of S2. It shows that the film removal effect of Low-E film and Low-E film has an influence on the water UV adhesion, and the quality of the silicone sealant is also one of the main factors affecting the adhesion of the silicone sealant to the film-removed Low-E glass. 

3.3.2 Influence of film removal wheel on adhesion

In the process of off-line Low-E glass film removal, a high-speed rotating film removal wheel is usually used to grind and remove film on the edge of LOW-E glass that needs to be sealed twice. In the process of high-speed rotation and film removal, a higher temperature is bound to occur, and the Low-E film is also wearing the film removal wheel while the film removal wheel is grinding the Low-E film layer. Therefore, the residue on the film removal glass panel is removed with The film wheel has a lot to do with it. There may be unremoved Low-E film, oxidized Ag or other substances decomposed due to high temperature, residues from the wear of the film removal wheel, etc., all of which may be It will affect the water UV adhesion of Low-E film removal glass. In this experiment, three commercially available film removal wheels L1, L2, and L3 were selected. After the Low-E film was removed by the secondary film removal process, the silicone structural adhesive was used to conduct the water UV bonding damage area test. The results are shown in Table 4. 

^{Table 4 The influence of different film removal wheels on water UV bonding test}

It can be seen from Table 4 that there are certain differences in the film removal effect of different film removal wheels under the same film removal method. The UV adhesion of the three kinds of silicone structural adhesives to the Low-E glass water after the second film removal of the L1 and L2 film removal wheels is significantly better than that of the L3 film removal wheel, which indicates that the quality of the film removal wheel will affect the off-line Low-E glass. The film removal effect further affects the water UV adhesion of the silicone structural adhesive to the Low-E film removal glass.

The film removal process will affect the water UV adhesion of the silicone structural adhesive to the offline Low-E glass. During the production process of the offline Low-E insulating glass, the edge Low-E film should be removed as cleanly as possible. However, it is difficult to remove the film on the edge of Low-E glass to achieve the same level of cleanliness as the surface of uncoated float glass, and the selection of high-quality silicone structural sealant with good applicability can make up for this shortcoming.

4. Conclusion

In this article, the adhesion of silicone sealant to uncoated float glass and offline LOW-E glass was investigated from the perspective of insulating glass production and actual use environment. The results showed that the commercially available silicone sealants had good adhesion to uncoated float glass under normal conditions, but showed different adhesions after UV treatment with water at 45°C. When testing the adhesion of Low-E glass, it was found that the Low-E film may be peeled off, causing the bonding and sealing failure of Low-E insulating glass. Therefore, film removal treatment is performed on the edge of the offline Low-E glass that needs to be bonded and sealed. is necessary. The water UV adhesion test of the de-filmed Low-E glass found that the film-removal wheel will affect the film-removal effect of the Low-E film, and the film-removal effect will affect the adhesiveness of the silicone sealant to the film-removed Low-E. Under the circumstance that it is difficult to achieve the same level of cleanliness as the surface of uncoated float glass on the surface of the Low-E glass that has been removed from the film, choosing a high-quality silicone sealant with good water resistance and UV adhesion can achieve good bonding to the Low-E glass that has been removed from the film. sealing effect.

The Automatic Low-E Glass Edge Removing Machine independently developed and produced by Jinan LIJIANG Glass can automatically identify and detect the glass size, automatically distinguish the Low-E film surface, and adjust the edge film removal width according to the processing requirements. 

^{For more information about Jinan LIJIANG Glass insulating glass processing equipment and insulating glass processing accessories, please click here to learn more.}