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As a distinctive feature of modernist high-rise buildings, glass curtain walls are widely used in iconic buildings around the world. Under the beautiful appearance of the glass curtain wall, there is also a little-known "small material"-silicone structural adhesive.
Silicone structural adhesive is the guardian of the safety of the glass curtain wall. Its function is to firmly fix the glass plate to the framed profile. Therefore, the performance of the silicone structural adhesive is extremely important for the safety of the glass curtain wall.
In the sealant-related product standards, the test items of different standards are not the same, and the maintenance conditions and test methods of the same test item in different standards may also be different.
Today, I will take you to understand the relevant knowledge of the silicone structural adhesive testing project——
01, sag
Sagging refers to the degree to which the sealant flows out of the joints on the vertical surface.
The test mold has a width of 20mm, a depth of 10mm, and a temperature of (50±2)°C. It is required to be placed vertically: the sag is less than or equal to 3mm, and placed horizontally: no deformation. The higher the temperature, the wider and deeper the glue, especially the upside down seam, the easier it is to sag.
02, extrusion
Extrudability is suitable for single-component, which refers to the degree of difficulty of extruding when applying the sealing material with an extruding gun.
Test with a 177mL standard rubber squeeze cylinder, without the squeezing nozzle, and the air pressure is 0.340MPa. The time required to test all the samples at one time is less than or equal to 10s. The smaller the extrudability, the heavier the hand feel. Customers generally require good extrudability, no sagging, good squeegee, and good molding after squeegee.
03. Applicable period
The pot life indicates the usable time, which is suitable for two-component sealant, which refers to the time that the two-component sealant can be embedded in the joint at the specified temperature after mixing. The requirement is greater than or equal to 20min, which is equivalent to the breaking time we measured.
In order to prevent the downtime from being too long, the glue dispenser can block the gun, and the pot life is 30-60min.
07, heat aging
Thermal aging is mainly the detection item of white oil. JG/T 475-2015 directly requires the testing of alkane plasticizers.
Thermal aging includes three items of thermal weight loss, cracking and chalking. Thermal weight loss is the quality loss rate of the sealant after being completely cured at room temperature and 90 ℃ high temperature treatment. Cracking refers to the irregular network cracks produced on the surface of the sealant. Chalking refers to the phenomenon that powder forms on the surface of the sealant due to weather, aging and other reasons.
Silicone structural adhesive without white oil generally loses weight within 6% without cracking and chalking.
