1. Appearance: The appearance of the sealant mainly depends on the dispersion of the filler in the base rubber. The filler is a solid powder. After being dispersed by a kneader, a grinder or a planetary machine, it can be uniformly dispersed in the base rubber to form a fine paste. Sometimes, depending on the nature of the filler itself, the presence of the pole is not excluded. A small amount of fine fine or fine sand is acceptable as normal. If the filler is not well dispersed, many very coarse particles will appear. In addition to the dispersion of the filler, other factors may also affect the appearance of the product, such as the incorporation of particulate impurities, crusts and the like. These situations are considered to be rough. The appearance of the observation method is to take the product out of the package and directly observe it, or put the product on 1-2g on white paper, and fold the white paper to open and observe it. The term is called "butterfly observation". When coarse particles are found, the coarse particles should be judged.
2. Hardness: Hardness refers to the hardness of the sealant after it has 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 the scoring or pressing of an attempted substance into its surface. According to the method of measuring the hardness, the hardness is expressed by various methods such as Brinell hardness, Rockwell hardness, and Shore hardness. The state specifies Shaw A hardness. The standard hardness value is measured by a hardness tester prepared according to the national standard method. The hardness of the sealant is high, the surface sealant is rigid, and the elasticity and flexibility are insufficient. The hardness is small, the elasticity and flexibility are good, and the rigidity is insufficient. Therefore, the sealant is neither as hard as possible, nor as soft as possible, but has a certain range of requirements according to actual needs.
3. Tensile strength: Tensile strength is also one of the mechanical properties after the sealant is completely cured. Tensile strength, also known as tensile strength, tear strength, commonly known as tensile force. Refers to the ability of a material to resist damage when subjected to tension. Tensile strength values ​​are also detected by methods specified by national standards. According to the needs of its use, the sealant requires a certain strength requirement, especially the structural adhesive. The minimum value of the strength is clearly specified in the national standard. The sealant with too weak strength cannot meet the needs of use. However, it is also inadmissible to over-emphasize the strength of the sealant while ignoring the elasticity.
4. Elongation: Elongation is the elastic performance of the sealant after it is fully cured. It is also one of the mechanical properties and refers to the ratio of the ratio of the total elongation to the original length of the material during stretching. A good elastic sealant will have a large elongation. As a minimum requirement for elongation, the sealant must meet the requirements of the national standard for the elongation performance.
5. Tensile modulus and displacement capacity: The tensile modulus and displacement capacity are the comprehensive performance of the above mechanical properties. The tensile modulus characterizes the strength produced when the sealant is stretched to a certain elongation. Therefore, the modulus is expressed together with elongation, such as a tensile modulus of 0.46 MPa at 25% elongation. The displacement capability is the ability of the sealant to withstand the displacement of the seal due to the expansion and contraction of the substrate. For example, we say that the sealant has a displacement capacity of ±25%, which means that the seam with this product can withstand 25% of the original stretch and compression. For example, the original seam width is 12mm, it can be compressed up to 9mm, stretching To 15mm. The displacement capacity can be detected by a tensile compression cycle or a cold drawn hot pressure cycle.
6. Adhesion to the substrate: This is an important property in the actual use of the sealant. The sealant must have good adhesion to the actual substrate to be used. A convenient way to verify the adhesion is to clean and dry the substrate with a suitable solvent or detergent, and place the sealant on it. After the sealant is cured (about 3-5 days), peel off the sealant by hand. Observe the bonding.
7. Extrusion: This is a project of sealant construction performance. It is used to indicate the difficulty of the sealant when it is used. The extrusion property of the glue is too thick, and it is very laborious to use the glue. However, if the glue is made too thin considering the extrudability alone, it will affect the thixotropy of the sealant. Extrusion can be measured by the method specified by national standards.
8. Thixotropy: This is another item of sealant construction performance. Thixotropy is the opposite of fluidity. It means that the sealant changes its shape only when a certain pressure is applied. When it has no external force, it can maintain its shape. It will not flow. The determination of the sag specified in the national standard is the judgment of the thixotropy of the sealant.
9. Curing performance: The one-component sealant is packaged and sealed in the container. It will be solidified when it is exposed from the inside of the container and exposed to the air. This is a chemical reaction process. The sealant is originally a paste. After contact with air, the base glue, cross-linking agent and catalyst in the sealant react with the moisture in the air. The result of this chemical reaction is This paste gradually becomes an elastic solid, which is the curing of the sealant. After the sealant is punched out, since the first contact with moisture is the surface of the sealant, the first surface is cured. After the surface is solidified, the water penetrates from the solidified surface, and the inner layer is cured. The sealant is gradually cured from the inside and the inside of the watch. The longer the time, the thicker the cure. The thicker the sealant is, the longer it takes to fully cure. For example, a 10mm thick glue usually takes more than a week to fully cure.