Building silicone structural sealant is mainly used in the installation of building hidden frame glass curtain wall.Whether all hidden or half hidden frame glass curtain wall, its installation are all glass in structural adhesive after special treatment of the aluminum frame curtain wall plate, so the sealing structure of silicone adhesive performance and durability performance requirements of special strict, it not only requires excellent atmosphere, the long-term stability of the hot and humid environment, but also must have a high bond strength and displacement ability.At present, curtain wall architecture is more and more designed and used in China, especially in some large and medium-sized cities, thus driving the rapid development of domestic production and application of such products.However, there has always been a mistaken understanding that the higher the hardness of silicone sealant structure, the greater the tensile bonding strength, the better the quality of the glue, the longer the service life.That's not the case.

  Test: The tensile cohesiveness, hardness, heating mass loss and cold drawing (hot pressing after bonding of 7 commercially available silicone sealant for construction produced by different manufacturers were tested respectively.Among the 7 samples, 1-6 were single component, and 7 was double component.The bonding substrate used is transparent float glass on one side and anodized aluminum alloy on the other side without bottom coating.The size, shape, preparation and test method of each test item are in accordance with the current national standards.　

  According to GB/T13477.8-2002 "Test Method for Building Sealing Materials" (Part 1: Determination of tensile cohesiveness), three groups of specimens were prepared and cured at 23℃ for 28d(single component) or 14d(double component) respectively. One group was tested at 23℃.The second group was immersed in water under standard conditions for 7 days and immediately underwent pull test.The third group was immersed in water and exposed to ultraviolet radiation for 300h(temperature 40℃).

  The following conclusions can be drawn:

  (1) The tensile bond stress-strain curve of silicone sealant shows a quadratic polynomial function relationship.

  (2) Water promotes the occurrence of the hydrolysis reaction of silicone structural sealing glue, so that the tensile bond strength decreases.

  (3) The synergistic effect of light, heat and water on the aging rate of performance index is greater than that of single water factor.

  (4) Due to the complexity of aging mechanism under different conditions, there is no direct correspondence between the indexes of tensile bond, especially the secondary length, which should be considered by many factors.

  (5) There is a good correspondence between hardness and 60% modulus. More importantly, the coordination among hardness, tensile bond strength and secondary length ratio can not only achieve good displacement performance, but also meet the technical requirements of national standards easily.

  The difference between structural adhesive and non-structural adhesive

  Structural adhesive refers to high strength (compression strength >65MPa, steel-steel tensile bonding strength >30MPa, shear strength >18MPa), can withstand large load, and aging resistance, fatigue resistance, corrosion resistance, stable performance in the expected life, suitable for bearing strong structural parts bonding.

  Non-structural adhesive has low strength and poor durability, and can only be used for ordinary and temporary bonding, sealing and fixing, not for structural parts bonding.

  The service life of construction projects is generally more than 50 years, and the components bear large complex stress, which is directly related to the safety of life and property of personnel. Structural adhesive should be used for bonding.Structural adhesive is widely used in engineering, mainly used for strengthening, anchoring, bonding, repair and so on;Such as sticking steel, sticking carbon fiber, planting reinforcement, crack reinforcement, sealing, hole repair, spike paste, surface protection, concrete bonding, etc.