What are the main properties of the sealant

(1) Appearance: The appearance of the sealant mainly depends on the dispersion of the filler in the base adhesive. Filler is a solid powder that can be uniformly dispersed in the base glue to form a delicate paste after being dispersed by kneading machines, grinders, and planetary machines. Sometimes, depending on the nature of the filler itself, it is not ruled out that there are very small amounts of slight fine particles or sand, which are acceptable normal phenomena. If the filler is not well dispersed, many very coarse particles will appear. In addition to the dispersion of fillers, other factors can also affect the appearance of the product, such as the inclusion of particulate impurities, scaling, and so on. These situations are considered rough in appearance. The method of observing the appearance is to directly observe the product by knocking it out of the packaging, or by beating 1-2g of the product onto white paper, folding the white paper in half, flattening it, and then opening it for observation. The term is "butterfly shaped observation.". When coarse particles are found, they should be judged.
(2) Hardness: Hardness refers to the hardness of the sealant after it has completely solidified into a rubber body, which belongs to one of the physical and mechanical properties of the product. Hardness refers to the ability of a material to resist attempted material scratching or pressing into its surface. According to different methods for measuring hardness, there are various methods for expressing hardness, such as Brinell hardness, Rockwell hardness, and Shore hardness. According to national regulations, Shore A hardness is used. The standard hardness value is measured by using a hardness tester when the test piece is made according to the national standard method. The hardness of the sealant is high, and the surface sealant has strong rigidity, but insufficient elasticity and flexibility; Small hardness is the opposite, with good elasticity and flexibility, and insufficient rigidity. Therefore, the sealant is neither as hard as possible, nor as soft as possible, but has a certain range of requirements based on actual needs.
(3) Tensile strength: Tensile strength is also one of the mechanical properties of the sealant after complete curing. Tensile strength is also known as tensile strength, tensile strength, commonly known as tensile strength. The ability of a material to resist damage when subjected to tensile force. The tensile strength value is also detected according to the methods specified in national standards. Sealants have certain strength requirements according to their use needs, especially structural adhesives, which clearly specify a low strength value in the national standard. Sealants with poor strength cannot meet the use needs. However, if you overemphasize the strength of the sealant while ignoring the elasticity, it is also not enterprising.
(4) Elongation: Elongation refers to the elastic performance of a sealant after complete curing, and also belongs to one of the mechanical properties. It refers to the percentage of the ratio between the total elongation and the original length of the material during stretching. Sealants with good elasticity will have a greater elongation. As a low requirement for elongation, the sealant must meet the requirements for constant elongation performance in national standards.
(5) Tensile modulus and displacement capacity. Tensile modulus and displacement capacity are the comprehensive performance of the above mechanical properties. The tensile modulus represents the strength of a sealant when it is stretched to a certain elongation. Therefore, the expression method of the modulus is combined with the elongation, such as the tensile modulus is 0.46Mpa when the elongation is 25%. Displacement capacity refers to the displacement capacity that the sealant can withstand when the joint is displaced due to thermal expansion and cold contraction of the substrate. For example, we claim that the sealant has a displacement capacity of ± 25%, indicating that the adhesive seam using this product can withstand 25% of the original width of tension and compression. For example, the original adhesive seam width is 12mm, which can be compressed to 9mm and stretched to 15mm. The displacement capacity can be detected using a tensile compression cycle or a cold drawn hot pressed cycle.
(6) Adhesion to substrate. This is a very important performance in the actual use of sealant, and sealant must have good adhesion to the actual substrate before use. A simple way to test adhesion is to clean and dry the substrate with a suitable solvent or detergent, apply the sealant to it, and after the sealant has solidified (about 3-5 days), peel the sealant off by hand to observe the adhesion.
(7) Extrudability: This is an item of sealant construction performance, used to indicate the degree of difficulty in applying the sealant. If the sealant is too thick, the extrudability is poor, and it is very laborious to apply the sealant during use. However, if you simply consider extrudability and make the adhesive too thin, it will affect the thixotropy of the sealant. Extrudability can be measured using methods specified in national standards.
(8) Thixotropy: This is another item in the construction performance of sealant. Thixotropy is the opposite of fluidity, which refers to the fact that a sealant can only change its shape under certain pressure, and can maintain its shape without flowing when there is no external force. The measurement of sag specified in national standards is the judgment of the thixotropy of sealant.