The discussion on the sealing life of insulating glass in TPS heating system②

3. Discussion on the sealing life of the insulating glass

3.1 The influence of use environment on insulating glass

As shown in Figure 8, the insulating glass will be affected by various external factors during use

^{Figure 8 Environmental factors in the use of insulating glass}

Especially due to the frequent changes of ambient temperature and pressure, the gas in the hollow cavity of the hollow glass is always in a state of thermal expansion or contraction, as shown in Figure 9, which makes the sealant under stress for a long time. For the traditional double-channel sealing system, the action of this force will cause the deformation of the sealant and the loss of its function, and the moisture in the environment will continuously penetrate from the edge of the hollow glass into the hollow cavity. 

At the same time, the effects of ultraviolet rays, water, and other corrosive gases in the environment (the term "corrosion" provided by Google) will accelerate the aging of the sealant, thereby accelerating the rate of water vapor entering the hollow cavity and the escape of the filled argon gas. This kind of water vapor penetration occurs at any time. The drying agent in the edge sealing system (the term "drying" is provided by Google) will eventually lose the water vapor adsorption capacity due to the continuous adsorption of water molecules, increasing the water vapor content in the hollow cavity of the hollow glass. The failure of the seal leads to a reduction in the energy-saving effect. 

Due to the elasticity of the thermoplastic spacer sealing system, the edge stress can be effectively released when the environment changes. At the same time, the thermoplastic spacer has a higher cohesive force to resist changes brought about by the load and ensure the stability of the sealing structure.

^{Figure 9 shows the changes in the use of traditional channel aluminum insulating glass and thermoplastic spacer (TPS) systems}

For the three-glass two-cavity hollow glass commonly used in passive room glass of the new energy-saving building concept (see Figure 10), the glass on both sides of the glass will be subjected to the action of the other cavity to produce greater stress, resulting in butyl The deformation of the glue reduces the effect of the first seal and increases the passage of water vapor, so that the insulating glass will fail more quickly, and the sealing advantage of the thermoplastic spacer will be more obvious.

^{Figure 10 shows the change of sealant under the influence of a three-glass two-cavity insulating glass environment}

3.2 Factors affecting the life of the insulating glass

Doors and windows (the term "doors and windows" are provided by Google) Curtain walls are an important part of the building, and the service life of the insulating glass used in it has attracted the attention of the industry. It is mentioned in the relevant industry-standard "Causes and Service Life of Insulating Glass", The expected service life of insulating glass should be at least 15 years. However, the overall sealing service life of domestic insulating glass in China is still relatively low, and ordinary manufacturers are afraid to promise a 10-year warranty. Therefore, we are still far from the standard requirements and building use requirements.

As mentioned above, the service life of insulating glass is directly related to the quality of the edge materials (such as spacers, desiccant, sealant) and the manufacturing process of the insulating glass. The service life of insulating glass is also affected by the installation conditions and the use environment.

In 3.1, we introduced the influence of the external environment on the service life of the insulating glass. In addition to external factors, what other factors affect the service life of insulating glass? The quality of the edge seal is directly related to the sealing durability of the insulating glass. Use low water vapor Sealant and gas permeability are the keys. From the previous analysis, we can see that thermoplastic spacers (TPS) have very excellent water vapor and gas barrier capabilities. Used for sealing the edges of the insulating glass will improve the sealing of the insulating glass.Taking the three-glass two-cavity insulating glass system as an example, we can see from Figure 11 that 8 bonding interfaces are formed between the traditional channel aluminum insulating glass sealant and the glass and spacer materials, and the thermoplastic spacer (TPS) seals Only 4 bonding interfaces are formed with glass. From the current domestic production level of insulating glass and our long-term inspection situation analysis, the poor adhesion of the sealant to the glass and the spacer material is the main path leading to the passage of water vapor and gas, that is to say, the water vapor and gas permeability of the sealing material In the same situation, the thermoplastic spacer sealing system reduces the passage of water vapor and gas due to the reduction of the bonding surface, to achieve the long-term durability of the insulating glass.

^{Figure 11 Analysis of the sealing and bonding interface of different insulating glass}

3.3 Current domestic quality of insulating glass

Insulating glass national standard uses moisture permeability index (I) to express the water vapor sealing life of the insulating glass. The standard stipulates that the average value of I should be greater than 0.2; the value of the argon content after the durability test is used to express the gas seal life.

Ti desiccant initial moisture content

Tf desiccant final moisture content

Tc desiccant standard moisture content

What is the moisture permeability index I value? 

I value refers to the ratio of the amount of external water vapor entering the insulating glass to its effective adsorption amount in the durability test. The moisture permeability index I value can reflect the remaining adsorption capacity and expected service life of the insulating glass sealing system; it can comprehensively evaluate the insulating glass system. The smaller the value of I, the greater the remaining adsorption capacity of the insulating glass, and the longer the sealing life.The National Glass Quality Supervision and Inspection Center has carried out statistical analysis on the durability test results of more than 300 domestic insulating glass water vapor seals in China in the past two years. The distribution of the I value is shown in Figure 12. The median value of I value is close to 15%. A value greater than 20% accounts for about 15%.

^{Figure 12 I value statistics of domestic insulating glass}

At the beginning of this century, the European Insulating Glass Association UNI conducted a statistical analysis on the test results of the water vapor seal durability of European insulating glass products (see Figure 13). It can be seen from Figure 13 that the median value is between 4% and 5%. , It can be seen from the two statistical results that there is still a big gap in the overall sealing life of domestic insulating glass compared with foreign countries.

^{Figure 13 UNI European insulating glass I value statistics}

In the past two years, the quality of passive room glass has also attracted much attention. Table 3 is the test results of the water vapor sealing durability of three-glass two-cavity insulating glass by the National Glass Quality Supervision and Inspection Center in recent years. It can be seen from Table 3 that the quality of insulating glass produced by different companies has a relatively large gap, and the overall quality level needs to be improved. If such glass is used in passive buildings, it will far fail to meet the requirements of the same life span as buildings. To solve this problem, we should start with materials and processes, and at the same time seek more advanced sealing structures.

^{Table 3 Test results of water vapor sealing durability of three-glass two-cavity insulating glass}

4. Thermoplastic spacer (TPS) sealing system insulating glass test analysis

The earliest thermoplastic spacer (TPS) insulating glass system was born in Komelin in 1974. Industrial production was after the 1990s. There are currently more than 100 TPS production lines in the world. There are also several TPS insulating glass production lines in operation in China. The earliest production line was put into production in 2011. Thermoplastic insulating glass and a new generation of TPS product 4SG with structural strength (the term "structural strength" is provided by Google) It has been initially recognized and applied in the fields of structural curtain walls, commercial buildings, residential buildings, buses, and automobiles.

Since its inception, the TPS system has passed the testing and certification of relevant standards in many countries around the world, mainly including Japanese JIS R3209 "Insulating Glass", European Standard EN1279-2 "Long-term Test Method for Water Vapor Permeability of Insulating Glass", European standard EN1279-3 "Long-term test method for gas penetration of insulating glass", European standard EN1279-4 "Test method for physical properties of insulating glass edge sealing", North American ASTM773/774, French NFP78-451/452, Italy UNI10593, German DIN1286, And other standards.

The sealing system insulating glass is also the first three-glass two-cavity insulating glass system to pass the EN1279.3 gas retention test, and its annual argon leakage rate is 0.4%~0.5%, respectively.

To study and analyze the performance of the insulating glass of the thermoplastic partition system and verify its durability advantages, the National Glass Quality Supervision and Inspection Center selected Comerlin to produce the 4SG product of the thermoplastic partition, using Dow Corning silicone structural adhesive as the external sealant. Using Bystronic's fully automatic production line, a sample of gas-filled insulating glass was produced. According to the water vapor seal durability and gas seal durability in the GB/T11944-2012 standard, 5 standard cycles of testing were carried out.

4.1 Water vapor seal durability

Each cycle of the test is composed of high and low-temperature alternating cycles and constant temperature and humidity. The first stage: 56 cycles, one temperature cycle every 12 hours, the temperature ranges from -18°C±2°C to 53°C±1°C; the second stage: an environment with a temperature of 58°C±1°C and relative humidity greater than 95% The temperature is maintained for 7 weeks, and each cycle is 77 days (Figure 14).

^{Figure 14 Water vapor seal durability cycle}

In this test, 5 groups of samples are put into the aging test box. After each cycle is completed, one group is taken out for the final moisture content test and the I value is calculated. The results are shown in Table 4.

4.2 Gas seal durability

 First, the initial argon content of the insulating glass tested for durability was tested. The results are shown in Table 5.

^{Table 4 Thermoplastic spacer (4SG) 5 cycles durability test results}

Secondly, following the testing method of China's domestic industry standard, the samples were tested for 5 cycles, and the argon content was tested after each cycle. The test results are shown in Table 6.

^{Table 6 Test results of argon content of samples after aging}

Judging from the test results, the insulating glass of this type of thermoplastic spacer (4SG) system can still meet the requirements of the national standard regardless of the moisture permeability index or the argon content after the 5 standard aging cycle tests. The moisture permeability index After 5 cycles, the test results are better than the current standard cycle test results of the traditional domestic sealing structure, and the gas content has only dropped by about 4%, indicating that the service life of the insulating glass of this system will be much longer than the current domestic mainstream sealing structure insulating glass.

5. Conclusion

From theoretical analysis to test results, it is shown that thermoplastic spacers (TPS) are a new generation of insulating glass edge sealing materials. This insulating glass system can increase the sealing life of the insulating glass and improve the edge effect of insulating glass. It should be promoted vigorously. However, at present, both the sealing material of the thermoplastic spacer and the fully automatic production equipment for producing the insulating glass of the sealing structure are from developed countries, and the price is still one of the main reasons restricting the promotion and application of the insulating glass of the thermoplastic spacer (TPS). At present, China is still at the stage of equipment R&D and material research, and industrial production has not been realized. With the increase in people's understanding of the superior performance of thermoplastic insulating glass, the investment in research, and the further improvement of the level of industrialization, its application prospects will become wider and wider.