(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 the kneader, mill, and planetary machine, it can be evenly dispersed in the base rubber to form a delicate paste. Sometimes, depending on the nature of the filler, it does not exclude the existence of extremely A small amount of fine grain or fine sand is acceptable and normal. If the filler is not well dispersed, many very coarse particles will appear. In addition to the dispersion of the filler, other factors also affect the appearance of the product, such as mixing in particulate impurities, crusting, etc. These situations are considered rough. The method of observing the appearance is to directly observe the product from the packaging, or put 1-2g of the product on white paper, fold the white paper flattened and then open the observation. When coarse particles are found, coarse particles should be judged.

(2) Hardness: Hardness refers to the hardness of the sealant after it is completely cured into a rubber body, which is one of the physical and mechanical properties of the product. Hardness is the ability of a material to resist the scoring or pressing of an attempted substance into its surface. Depending on the method of measuring the hardness, there are various methods such as Brinell hardness, Rockwell hardness, and Shore hardness. National regulations use Shore A hardness. The standard hardness value is detected by a hardness tester made according to the national standard method. The sealant has high hardness, the surface sealant has strong rigidity and insufficient elasticity and flexibility; the opposite is the case with small hardness, 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 of the sealant after it is completely cured. Tensile strength is also called tensile strength, tearing strength, commonly known as tensile force. It refers to the ability of a material to resist damage when it is pulled. The tensile strength value is also detected according to the method prescribed by national standards. The sealant must have certain strength requirements according to the needs of its use, especially for structural adhesives. The minimum value of the strength is clearly specified in the national standard. Sealants with too weak strength cannot meet the needs of use. However, it is not advisable to over-emphasize the strength of the sealant and ignore the elasticity.