Do You Know These Terms For Silicone Sealant?

Silicone sealant is a salt-like material that solidifies into a tough rubber-like solid when it comes into contact with moisture in the air. Mainly divided into deacetic acid type, dealcohol type, deammonia type, dec type. Silicone glue is commonly known as glass glue because it is often used for bonding and sealing of glass.

Silicone sealant can be divided into silicone structural sealant, silicone weather resistant sealant and silicone glass sealant, among which silicone structural sealant is divided into high-performance silicone structural sealant, neutral transparent structural sealant and so on.

Appearance 

The appearance of the sealant mainly depends on the dispersion of the filler in the base adhesive. Filler is a kind of solid powder, after the kneading machine, grinder, planetary machine dispersion, it can be evenly dispersed in the base glue to form a delicate paste, sometimes according to the nature of the filler itself is different, does not exclude the existence of a very small amount of slight fine particles or sand, which is acceptable normal phenomenon. If the filler is not well dispersed, there will be a lot of very coarse particles. In addition to the dispersion of the filler, some other factors will also affect the appearance of the product, such as mixed particle impurities, crust and so on. These cases would be considered coarse in appearance.

Observation method of appearance: Directly observe the product from the packaging, or hit the product 1-2g on the white paper, fold the white paper flat and then open the observation, the term is called "butterfly observation", when the coarse particles are found, the coarse particles should be judged.

Hardness 

Refers to the hardness of the sealant after it is completely cured into the 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 attempts to carve or press into its surface. According to the different hardness measurement methods, hardness expression methods have Brinell hardness, Rockwell hardness, Shore hardness and other methods. The state stipulates that Shore A hardness is used, and the standard hardness value is detected by a hardness tester in accordance with the national standard method. The hardness of the sealant is high, the surface sealant is rigid, and the elasticity and flexibility are insufficient; On the contrary, the hardness is small, the elasticity and flexibility are good, the rigidity is insufficient, so the sealant is neither the harder the better, nor the softer the better, but according to the actual needs have a certain range of requirements.

Tensile

Tensile strength is also one of the mechanical properties of the sealant after it is fully cured. Tensile strength is also known as tensile strength, tearing strength, commonly known as tension. The ability of a material to resist damage when subjected to tension. The tensile strength value is also detected according to the method specified in the national standard. Sealant according to the needs of its use is to have a certain strength requirements, especially structural adhesive, it is clearly stipulated in the national standard of the minimum value of strength, strength is too poor sealant can not meet the needs of use. However, if too much emphasis on the strength of the sealant and ignore the elasticity is not enterprising.

Elongation at break

Elongation is the elastic performance of the sealant after complete curing, and also belongs to one of the mechanical properties, which refers to the percentage of the ratio between the total elongation and the original length of the material when stretched. Good elastic sealant will have a larger elongation. As the minimum requirement for elongation, the sealant must meet the requirements of fixed elongation in the national standard.

Tensile modulus and displacement capacity

Tensile modulus and displacement capacity are the comprehensive performance of the above mechanical properties. The tensile die scale indicates the strength produced when the sealant is stretched to a certain elongation. Therefore, the expression of the modulus is at the same time with the elongation, such as the tensile modulus of 25% elongation is 0.46Mpa. Displacement capacity is the displacement capacity that the sealant can withstand when the joint displacement is caused by the thermal expansion and cold contraction of the substrate. For example, we say that the sealant has a displacement capacity of ±25%, which indicates that the glue seam using the product can withstand the stretching and compression of the original width of 25%, for example, the width of the original glue seam is 12mm, it can be compressed to a maximum of 9mm and stretched to 15mm. The displacement capacity can be detected by the method of tensile compression cycle or cold tensile hot compression cycle.

Adhesion to the substrate

This is a very important performance in the use of sealant, sealant must have good adhesion to the actual use of the substrate to be used. The easy way to test the adhesion is to clean and dry the substrate with an appropriate solvent or detergent, and the sealant is hit on it, and after the sealant has cured (about 3-5 days), peel the sealant by hand to observe the adhesion.

Extrudability

This is a project of sealant construction performance, used to indicate the difficulty of the use of sealant, too thick rubber extrusion is poor, the use of glue is very laborious. However, if the rubber is too thin simply considering the extrudability, it will affect the thixotropy of the sealant. The extrudability can be determined by the method specified in the national standard.

Thixotropy 

This is a project of the construction performance of the sealant, which is used to indicate the degree of difficulty when the sealant is used, and the extrudability of too thick glue is poor, and the glue is very laborious when used. However, if the rubber is too thin simply considering the extrudability, it will affect the thixotropy of the sealant. The extrudability can be determined by the method specified in the national standard.