Explanation of the tensile properties and durability of silicone structural sealant
Experiment: Seven commercially available silicone structural sealants produced by different manufacturers were tested for their tensile adhesion, hardness, heating mass loss, and cold drawing (adhesion after hot pressing). Among the seven samples, 1-6 were single component and 7 were two-component. The bonding substrate used was transparent float glass on one side and anodized aluminum alloy on the other side, both without a primer. The size, shape, preparation, and testing methods of each test specimen were carried out in accordance with the current national standards. Three groups of specimens were prepared according to GB/T13477.8-2002 "Test Methods for Building Sealing Materials" (Part 1: Determination of Tensile Adhesion), and cured at 23 ℃ for 28 days (single component) or 14 days (single component), respectively. Two components were tested, with one group subjected to a J-towel test at 23 ℃; The second group was immersed in water under standard conditions for 7 days and immediately subjected to a tensile test; The third group was placed in a water ultraviolet irradiation test chamber and immersed in water for 300 hours (temperature 40 ℃) before conducting a tensile test.
The following conclusion can be drawn from this:
(1) The stress-strain curve of the tensile bonding performance of silicone structural sealant shows a quadratic polynomial function relationship.
(2) Water promotes the hydrolysis reaction of silicone structural sealant, resulting in a decrease in the tensile bond strength.
(3) The synergistic effect of light, heat, and water has a greater aging rate on performance indicators than a single water factor.
(4) The complexity of aging mechanisms under different conditions results in no direct correspondence between the various indicators of tensile bonding, especially the elongation rate, which requires consideration of multiple factors.
(5) There is a good correspondence between hardness and 60% modulus, and more importantly, the coordination between hardness, tensile bonding strength, and elongation ratio can not only achieve good displacement performance, but also easily meet the technical requirements of national standards in multiple indicators.
The difference between structural adhesive and non structural adhesive
Structural adhesive refers to high strength (compressive strength>65MPa, steel steel tensile bonding strength>30MPa, shear strength>18MPa), able to withstand large loads, and resistant to aging, fatigue, and corrosion. It has stable performance within the expected life and is suitable for bonding structural components that can withstand strong forces.