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Abstract: Starting from the actual use environment of insulating glass, this article examines 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 adhesiveness of silicone sealant to uncoated float glass and offline Low-E glass is most affected by the water UV aging treatment. The water and UV resistance of silicone sealants from different manufacturers are different. In the case that it is difficult to achieve the same cleanliness as the surface of uncoated float glass on the surface of uncoated Low-E glass, the choice of high-quality silicone sealant with good water resistance and UV adhesion can achieve good adhesion to the Low-E glass.

1. Introduction   

The energy issue is the primary issue in the economic development of the world today, and energy conservation is an inevitable requirement for achieving sustainable development. Therefore, building energy conservation is also receiving increasing attention. Glass doors and windows are the weakest energy-saving part of the four major components of building envelopes. Insulating glass is one of the effective ways to slow down its energy loss. Low-E glass can not only meet people's aesthetic needs for buildings, but also solve the problems of heat control, cooling costs, and comfortable balance of internal sunlight projection. 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-E (The "dry" gas is provided by Google). Its unique spatial structure can block the heat conduction channel, thereby effectively reducing its heat transfer coefficient. It is a glass product with energy-saving, sound insulation, and environmental protection functions. Therefore, Jinan LIJIANG Glass analyzed the reasons for the failure of the insulating glass and pointed out that the sealant is one of the factors affecting the failure of the insulating glass.    

In my country's insulating glass market, the sealing process of insulating glass can be divided into three sealing, double sealing, and single sealing. The latter two sealing types are more common. The most common room temperature curing sealant uses a two-pass sealing process. The inner channel (or one channel) sealant of the double-channel seal mainly uses thermoplastic polyisobutylene sealant, whose main function is to reduce the permeability of water vapor and edges. The outer (or second) sealant mainly includes polysulfide sealant (PS) and silicone sealant (the term "silicone sealant" is provided by Google), which mainly serves as a bonding and sealing effect. Silicone sealant has good bonding properties 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    

Non-coated float glass and Low-E glass, commercially available; There are five commercially available silicone structural adhesives (S1, S2, S3, S4, S5), of which S1 is the sealant for Low-E film-removing glass, S2 is a foreign brand silicone sealant, S3, S4, S5 is a silicone sealant of different domestic brands;    

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

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

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

2.2 Experimental test 

Use the silicone structural sealant according to the use method provided in the product manual, refer to the "silicone structural sealant for insulating glass" (GB24266-2009) standard, use 50mm×50mm×6mm Low-E glass or non-coated float Method glass is the bonding test object. Prepare the H-type tensile bonding test sample shown in Figure 1, and after curing for 14 days under the standard conditions specified in GB/T 16776-2005, it is treated in a water UV box at 45°C for 300 hours. (UV wavelength 340nm), water immersion treatment for 300h, UV box treatment for 300h (UV wavelength 340nm), and then tensile bonding test. 

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

3. Results and discussion   

3.1 Investigation of the adhesion of silicone sealant to uncoated glass 

This experiment investigated the effect of silicone sealants produced by different manufacturers on uncoated float glass under normal conditions, immersion treatment for 300h, UV box for 300h (UV wavelength 340nm), and 45℃ water UV box for 300h (UV wavelength 340nm). The tensile adhesiveness after treatment under such conditions, and the results are shown in Table 1. 

It can be seen from Table 1 that there are certain differences in the adhesiveness and tensile bonding strength of silicone sealants from different manufacturers to uncoated glass. Insulating glass manufacturers should choose silicone sealants with better adhesion. At the same time, sealants with different tensile bonding strengths are selected according to design requirements. When comparing the adhesiveness of silicone sealant to glass from different manufacturers, it can be found that silicone sealant exhibits good adhesion to uncoated glass, but S3, S4, and S5 glue samples show a certain degree of adhesion after treatment under 45℃ water UV conditions. The adhesion failure of the adhesive, especially the 30% adhesion failure of the S5 glue sample. From the perspective of the tensile bond strength of silicone sealants treated under different conditions, the 45°C water UV treatment condition has the greatest impact on the tensile bond strength of the colloid, and the tensile bond strength of S4 and S5 has the largest decrease. The insulating glass will be exposed to sunlight, rain, or moisture for a long time in actual use. Therefore, it is necessary to study the water-ultraviolet adhesion of silicone sealants. Water-resistant ultraviolet adhesion should also be selected when producing insulating glass. Better silicone sealant.   

3.2 Investigation of the adhesion of silicone sealant to offline Low-E glass 

Because Low-E insulating glass has a better energy-saving effect than ordinary insulating glass, it is more and more popular in the market. This experiment examines S1, S2, S3, which have better UV adhesion to uncoated glass water, to offline Low-E The adhesion of glass, the test results under different processing conditions are shown in Table 2. 

It can be seen from Table 2 that S1 and S2 silicone sealants have high colloidal tensile bonding strength, and it is easy to peel the Low-E film from the glass surface during the test process of the H-type specimen, especially in the water UV at 45°C. Under these conditions, the Low-E film was peeled off in the test pieces prepared by the three types of silicone adhesives. The production process of offline Low-E glass is usually through the vacuum magnetron sputtering method to deposit a large number of the neutral target material (the term "target material" provided by Google) atomic (or molecular) film layer, The film is formed by the process is a soft film, and the film has poor abrasion resistance (the term "wear resistance" is provided by Google), chemical stability (the term "chemical stability" is provided by Google), and thermal stability. When the bonding strength of the sealant is high, the Low-E film is likely to be peeled off by the sealant. Figure 2 shows the Low-E film peeled off by S1 silicone sealant. 

Figure 2 Low-E glass water UV tensile bonding film peeling off  

Figure 2 Low-E glass water UV tensile bonding film peeling off    

It can be seen from Fig. 2 that the S1 silicone glue adheres well to the Low-E glass film-removed part, while the Low-E film of the non-film-removed part is torn from the glass panel by the silicone adhesive S1. The shedding of the film layer will cause the bonding and sealing of the insulating glass to fail. It means that during the production process of Low-E insulating glass, it is necessary to remove the film on the edges that need to be sealed and bonded. The main domestic Low-E Insulating glass manufacturers all remove the film on the edges. Therefore, this paper investigates the water-ultraviolet adhesion of silicone sealant to Low-E film-removing glass.

3.3 The water and ultraviolet adhesion of silicone sealant to the film-removed Low-E glass

3.3.1 The influence of film removal method on adhesion    

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

Different film removal methodsLow-E glass without film removalManually remove film glassAutomatic film removal line removes the film onceAutomatic film removal line removes the film twiceUncoated float glass
S1 water UV bonding failure area %Film peeling off30000
S2 water UV bonding failure area %5030100
S3 water UV bonding failure area %10060505
Figure 3 S1 UV bonding test results of Low-E glass water for one-time removal

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

Figure 4 S3 UV bonding test results of Low-E glass water for one-time removal

Figure 4 S3 UV bonding test results of Low-E glass water for one-time 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 film-removed Low-E glass, especially The Low-E film was peeled off in 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 silicone sealant to Low-E glass with two film removal is better than that of Low-E glass with one film removal, while the adhesiveness of Low-E glass with automatic film removal line and one film removal is significantly better than that of Low-E glass. Manually remove the film of Low-E glass. For the same Low-E glass and film removal equipment, the removal effect of two film removal processes on Low-E film is significantly better than that of one film removal process, while the film removal effect of automatic film removal equipment is significantly better than manual film removal It can be seen that the film removal effect on the surface of the film-removed glass will affect the adhesion of the silicone sealant to the film-removed Low-E glass. When the Low-E glass with manual film removal and the Low-E glass removed by the automatic film removal line as the bonding substrate, it can be seen that different silicone sealants have a water-UV adhesion to the film removal glass. With larger differences, the adhesion of S2 is better than S3, and the adhesion of S3 is significantly better than S2. It shows that the removal effect of Low-E film and Low-E film has an impact on the water UV adhesion, and the quality of silicone sealant is also one of the main factors affecting the adhesion of silicone sealant to film-removed Low-E glass. one.   

3.3.2 The influence of the film removal wheel on the adhesion   

In the process of removing the film of offline Low-E glass, a high-speed rotating film removal wheel is usually used to polish and remove the film on the edge of the Low-E glass that needs to be sealed twice. In the process of high-speed rotating film removal, a higher temperature is bound to occur, and the film removal wheel is grinding the Low-E film at the same time the Low-E film is also wearing the film removal wheel, so the residue on the film removal glass panel will be removed. The film wheel has a great relationship. The residue may contain unremoved Low-E film, oxidized Ag or other substances that decompose due to high temperature, and residue from the wear of the film removal wheel. These substances may all be It will affect the water-ultraviolet adhesion of Low-E film-removing glass. In this experiment, three commercially available film removal wheels L1, L2, L3 were selected. After the Low-E film was removed by the secondary film removal process, a silicone structural adhesive was used to test the water-ultraviolet bond failure area. The results are shown in Table 4. Show. 

Different film removal wheelsL1L2L3
S1 water UV bonding failure area %0010
S2 water UV bonding failure area %101040
S3 water UV bonding failure area %504080

Table 4 The influence of different film removing wheels on water UV bonding test    

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

The film removal process will affect the water-ultraviolet adhesion of the silicone structural adhesive to the offline Low-E glass. In 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 the Low-E glass to achieve the same cleanness as the surface of the uncoated float glass, and the selection of high-quality silicone structural sealant with good applicability can make up for this shortcoming.   

4. Conclusion    

This article examines the adhesion of silicone sealant to uncoated float glass and offline Low-E glass from the perspective of the production of insulating glass and the actual use environment. The results show that the commercially available silicone sealant has good adhesion to uncoated float glass under normal conditions, but exhibits different adhesion after being treated with water UV at 45°C. When testing the adhesion of Low-E glass, it was found that the Low-E film was peeled off, causing the possibility of failure of the bonding and sealing of the Low-E insulating glass. Therefore, the edge of the offline Low-E glass that needs to be bonded and sealed was removed. It is very necessary. The water-ultraviolet adhesion test of the film-removed Low-E glass found that the film-removing wheel will affect the film-removing effect of the Low-E film, and the film-removing effect will affect the adhesiveness of the silicone sealant to the film-removing Low-E glass. In the case that it is difficult to achieve the same cleanliness as the surface of uncoated float glass on the surface of uncoated Low-E glass, the choice of high-quality silicone sealant with good water resistance and UV adhesion can achieve good adhesion to the Low-E glass.

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