Performance and Service Life Analysis of Structural Adhesive

1, structural adhesive is a control material that affects the life of the curtain wall.

Effect of 1.1 Silicone Structural Adhesive on Building Durability

The performance and life of silicone structural adhesive is a topic of long-term concern in the industry, manufacturers, construction units, direct users and designers are very concerned. The small rubber strip is like a sewing thread, which connects the building firmware elastically and bears the corresponding force. Like sewing thread, the amount and cost of this material is not large, but the role is very critical. Since most of the main materials of the building are inorganic, the durability of these main materials is generally guaranteed. However, silicone structural adhesive is an organic material, and its durability is not as good as that of inorganic materials. Therefore, silicone structural adhesive should be a controlled and restricted material that affects the service life and structural safety of curtain wall buildings.

Comparative Analysis of Advantages and Disadvantages of 1.2 Silicone Adhesive

Silicone adhesive contains both organic groups and inorganic Si-O structure. This structure enables him to have both the properties of inorganic and organic materials, especially in the performance of excellent ultraviolet resistance, heat resistance and aging resistance, so it is the building curtain wall The material of choice for historical inspection has been applied for more than 40 years abroad and 30 years in China.

However, silicone structural adhesives are not as good as C- C polymers in terms of acid and alkali resistance, hydrolysis resistance and chemical inertness. Therefore, under the action of acid and alkali, metal catalysts and other substances, and under the condition of water vapor at the same time (especially the water vapor transmission rate of silicon products is very high), the silicone structural sealant may undergo chemical reactions to produce aging and performance decline.

Analysis of Bonding Performance of 1.3 Structural Adhesive

The bonding performance evaluation of structural adhesives involves two important indicators-bonding failure area and bonding strength. The bonding strength and bonding durability of structural adhesives should be sufficiently guaranteed. There are some typical manifestations of non-bonding. If the adhesive strip is peeled off with less force, and the peeling surface appears smooth and there are not many residual adhesive blocks, the pulling strength is more sufficient, but the bonding damage area will exceed the standard. How to solve the bonding problem, there is no universal glue. The current status of the industry is this: standard materials such as glass have very good bonding performance, and standard anodized aluminum profiles (bonding is also guaranteed. However, for new types of surface-treated materials, the bonding conditions cannot be completely stable. Therefore, the current general method is to make some primer on the bonding surface. The primer is a solution that has been proved to be very useful for a long time. Another advantage of primer is to improve the bonding condition on the interface and avoid adding too many harmful substances to the whole colloid. In the selection of new materials to take into account the appearance and safety, especially safety, the construction unit should fully understand and cooperate, the surface should be cleaned, construction should be maintained.

Overview of Aging Performance of 1.4 Structural Adhesive

Here involves a key word: chemical aging, physical aging is one aspect, chemical aging is more core. The performance of aging is mainly the obvious deterioration of adhesive strength and tensile strength, elongation at break, elastic recovery rate and other properties. In severe cases, the colloid will become very hard and lose elasticity. The performance of aging also has the initial and long-term, the polymer in the initial aging degradation process is the first core of the cross-linking point degradation, so that the cross-linking density of the glue decreased, the strength decreased, but the basic polymer chain is still there, so although its elongation increased, but the rebound rate decreased, aging has begun. But if the depth of aging, the polymer has been slowly decomposed, or even volatilized, leaving more filler, so poor elasticity will be powdered, hardening. The tracking and testing of existing curtain walls in China has been put on the agenda of the industry.

2. Scientific research on the quality standard of structural adhesive

Quality Standard of 2.1 Silicone Structural Adhesive in China

Regarding silicone structural adhesive, we currently have a mandatory national standard in China, and there are also European standards that have been talked about more in recent years. China's national standard has been implemented for nearly 15 years and has played an irreplaceable role in the development of the industry. But now it seems that there is still a gap between the national standard and the European standard. The gap is mainly reflected in the fact that China's national standard is mainly used to measure the performance of fresh glue under standard conditions, while the amount and degree of observation after aging are not enough. By comparison, the European standard has done better in this respect. After the aging test, we will see how much the relative performance of the glue can be maintained, and the retention rate of the relative performance is required to be not less than 75%. This involves the relationship between short-term and long-term, static and dynamic, absolute and relative values of the glue, emphasizing the maintenance of equilibrium stability and long-term dynamic performance.

2.2 Comparative Study of China's Current Standards and European Standards

Some testing items of the European standard require higher than the national standard. For example, water ultraviolet should be irradiated for more than 1000 hours, and the irradiation time and intensity are 2-3 times of the national standard. It can be seen that the European standard is very concerned about aging and life, and the long-term performance during use cannot be maintained. As for the national standard, just like the college entrance examination in our country, it is very strict in the entrance examination. However, it is not certain how the children will develop in the future. The European standard looks at the longer term.

But the European standard is not a single more stringent than the national standard, but more scientific. For example, the national standard has a more stringent standard than the European standard, that is, the damage area of bonding cannot be greater than 5%, and the European standard is 10%. I think 5% is not very scientific, because this is the absolute strength of the provisions, did not take into account the bonding conditions and environment. Polymer materials (is actually an improved process, the early requirements are so strict may cause adverse effects.

3, structural adhesive life status quo interpretation.

Current Status of Performance Life of 3.1 Structural Adhesive

The study of structural adhesive life is a key concept related to building safety. The service life of curtain wall is calculated by 100 years. Whether the service life of structural adhesive is 15 years or 25 years, the number and cost of maintenance are quite different. According to the current industry propaganda, if the European standard life can reach 25 years, the national standard is 10 to 15 years. According to our understanding of the factors affecting life, to solve this problem, the formula is the key, to respect the chemical laws of structural adhesives, curtain wall companies should not be overly accommodating to short-term construction requirements. Both domestic and foreign structural adhesives are facing the same problem. The proportion of domestic adhesive used in high-rise curtain walls is not very high. There is a gap between domestic and foreign countries. The degree of research history and details is different, but the aging problem is the same. Curtain wall companies all hope that the faster the structural adhesive solidifies, the better. In order to cater to customers, the adhesive factory can only add more catalyst to the colloid. However, we should know that the catalyst that accelerates the rapid solidification of the colloid can also accelerate the rapid decomposition of the colloid. He is a double-edged sword. At present, China is also a big country of curtain wall, so safety and security is also a major issue.

It is hoped that the whole industry can develop healthily and rationally. In the absence of conclusive experiments and practical tests, the publicity of the life of structural adhesive should be cautious. At present, the statement of 50 years is not appropriate. 25 years is combined with the European standard, but in fact the European standard has not been officially implemented in China. Therefore, although the curtain wall has a history of 50 years, it does not mean that its structural performance is as good as before. Hope that the industry can understand the reality of the national standard, but also to maintain confidence in the structural adhesive products.

3.2 methods to extend the life of structural adhesives

China's structural adhesive to reach the world level, so that everyone can rest assured to use, can not do without the efforts of the glue factory, the scientific norms of national standards, the guidance and management of industry associations, as well as the understanding of upstream and downstream industries support and cooperation. From the perspective of manufacturers alone, it is necessary to make in-depth improvements in the two major aspects of formulation and testing. From the past, the structural adhesive industry is still under a lot of pressure, from the future, China's curtain wall industry is still in the stage of development. The performance of structural adhesive should not be a sprint but a marathon. End]

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