8 performances of silicone sealant

(1) Appearance: The appearance of the sealant mainly depends on the dispersion of the filler in the base rubber. The filler is a kind of solid powder. After being dispersed by a kneader, grinder, or planetary machine, it can be uniformly dispersed in the base gum to form a fine paste. Sometimes depending on the nature of the filler itself, the existence of extremes is not ruled out. A small amount of slight fine grains or fine sand is an acceptable normal phenomenon. If the filler is not well dispersed, a lot of very coarse particles will appear. In addition to the dispersion of fillers, other factors will also affect the appearance of the product, such as mixing of particulate impurities, skinning, etc. These conditions will be considered rough appearance. The method of observing the appearance is to directly observe the product out of the package, or to hit 1-2g of the product on white paper, fold the white paper flat and open it for observation. The term is "butterfly observation". Coarse grains should be judged when they are found.

(2) Hardness: Hardness refers to the hardness after the sealant is completely cured into a rubber body, which is one of the physical and mechanical properties of the product. Hardness refers to the ability of a material to resist being scratched or pressed into its surface by an attempted substance. According to the different methods of measuring the hardness, there are many methods for the representation of hardness, such as Brinell hardness, Rockwell hardness, and Shore hardness. The state requires Shore A hardness. The standard hardness value is measured by a hardness tester in accordance with the national standard method. The hardness of the sealant is high, the surface sealant has strong rigidity, but the elasticity and flexibility are insufficient; the opposite is true when the hardness is small, the elasticity and flexibility are good, and the rigidity is insufficient. Therefore, the sealant is neither the harder the better, nor the softer the better, but 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 it is fully cured. Tensile strength is also called tensile strength, tear strength, commonly known as tensile strength. Refers to the ability of a material to resist damage when subjected to tension. The tensile strength value is also tested according to the method specified by the national standard. Sealants must have certain strength requirements according to the needs of their use. Especially for structural adhesives, the minimum value of strength is clearly specified in the national standard. Sealants with too poor strength cannot meet the needs of use. However, if you overemphasize the strength of the sealant while ignoring the elasticity, it is not enterprising.

(4) Elongation: Elongation is the elastic performance of the sealant after it is fully cured, and it is also one of the mechanical properties. It refers to the percentage of the ratio between the total elongation of the material when it is stretched and the original length. Sealant with good elasticity will have greater elongation. As the minimum requirement for elongation, the sealant must meet the requirements of fixed elongation performance in the national standard.