The structural adhesive has high strength, can withstand large loads (the term "load" is provided by the industry encyclopedia), and is resistant to aging, fatigue, and corrosion. It has stable performance within the expected life and is suitable for the bonding of strong structural parts. Adhesives (the term "adhesives" is provided by Industry Encyclopedia). It is mainly used for bonding between metals, ceramics, plastics, rubber, wood, etc. or between different kinds of materials, and can partially replace traditional connection forms such as welding, riveting, and bolting.

　　Poor adhesion to the substrate (the term "substrate" is provided by Industry Encyclopedia)?

　　sealant is not a universal glue (the term "universal glue" is provided by the industry encyclopedia), so it cannot guarantee good adhesion to all substrates in practical applications. With the diversification of substrate surface treatment methods and new processes, the bonding speed and bonding effect of sealants and substrates are also different.

　　There are three forms of damage to the interface between the structural adhesive and the substrate. One is cohesive failure, that is, cohesive force> cohesive force; the other is cohesive failure, that is, cohesive force <cohesive force. The third is that both types of failure are available. The bond failure area is less than or equal to 20% as qualified, and the bond failure area exceeds 20% as unqualified; when the bond failure area exceeds 20%, it is an undesirable phenomenon in practical applications. There may be six reasons why the structural adhesive does not stick to the substrate:

　　⑴The substrate itself is difficult to bond, such as PP and PE. Because of their high molecular crystallinity and low surface tension, they cannot form molecular chain diffusion and entanglement with most substances, so they cannot form a strong interface at the interface. Adhesion;

　　⑵The product has a narrow bonding range and can only work on part of the substrate;

　　⑶The maintenance time is not enough. Normally, after the two-component structural glue is used, it should be cured for at least 3 days, while the single-component should be cured for 7 days. If the temperature and humidity of the curing environment are low, the curing time needs to be extended.

　　⑷The ratio of A and B components is wrong. When using a two-component product, the user must mix the ratio of base rubber and curing agent in strict accordance with the ratio required by the manufacturer, otherwise there may be problems in the early curing, or the adhesion, weather resistance and durability in the later period of use. problem;

　　⑸ The substrate was not cleaned as required. Because the dust, dirt and impurities on the surface of the substrate will hinder the bonding, it must be strictly cleaned before use to ensure that the structural adhesive and the substrate are well bonded.

　　⑹ The primer was not applied as required. The use of primer on the surface of aluminum profiles for pretreatment can not only shorten the bonding time, but also improve the water resistance and durability of the bonding. Therefore, in actual engineering applications, we must use the primer correctly and strictly avoid degumming caused by improper use.　　The reason for the incompatibility with the accessories is that the sealant has a physical or chemical reaction with the accessories in contact. The resulting hazards include discoloration of the structural adhesive, non-stick to the substrate, decreased performance of the structural adhesive, and shortened service life of the structural adhesive.

　　Silicone structural adhesive has excellent properties such as high strength, high stability, excellent aging resistance, high temperature resistance, etc., and is widely used in the structural bonding of building curtain walls. However, in practical applications, due to human factors and the problem of the selected substrate (not strictly complying with the construction specifications), the performance of the structural adhesive has a great impact, and even makes it invalid.

　　Therefore, the compatibility test and adhesion test of glass, aluminum and accessories should be checked before construction, and the requirements of each link should be strictly followed during the construction process to achieve the effect of structural adhesive and ensure the quality of the project.