Addition liquid silicone is a type of organic organic silicone that is made of vinyl-containing polydimethylsiloxane as the base polymer, hydrogen-containing silicone oil as the cross-linking agent, and the cross-linking agent is vulcanized into an elastomer at room temperature or heated in the presence of a platinum catalyst. Silicon material. Compared with condensation-type liquid silica gel, addition-type liquid silica gel has the advantages of producing no by-products during the cross-linking and vulcanization process, minimal shrinkage, capable of deep vulcanization, and no corrosion to the materials in contact. In recent years, addition-type liquid silica gel has become the fastest growing variety among all types of silica gel.
In recent years, the improvement of the mechanical properties of addition-type liquid silica gel and its application development have received widespread attention. There have been numerous reports on the effect of silica on the properties of addition-type liquid silica gel. Hydrogen-containing silicone oil also has a great impact on the mechanical properties of addition-type liquid silicone; however, there are relatively few studies in this area.
Polyhydrogen-containing silicone oils with the same viscosity and different active hydrogen mass fractions were used as cross-linking agents to prepare liquid glue, and vulcanized test pieces were made to measure their mechanical properties. When the mass fraction of active hydrogen in polyhydrogen-containing silicone oil increases from 0.43% to 1.57%, the tensile strength of the liquid glue increases from 4.7MPa to 6.1MPa, the Shore A hardness also gradually increases, and the elongation at break increases from 490 % dropped to 255%. This is because the viscosity of hydrogen-containing silicone oil remains unchanged. As the mass fraction of active hydrogen increases, the molecular chain segments between the actual cross-linking points become shorter, and the strength, hardness and elongation of the liquid glue decrease; when the amount of hydrogen-containing silicone oil increases, the When the active hydrogen mass fraction increases from 0.75% to 1.57%, the tear strength does not change significantly. This can be explained as: when the active hydrogen mass fraction of polyhydrogen-containing silicone oil increases to 0.75%, the Si-H bonds in the cross-linking agent molecular chain are relatively concentrated, and the resulting steric hindrance effect reduces the effective cross-linking points of the liquid glue. The increase is not obvious, resulting in smaller changes in the tear strength of the liquid glue.
Hydrogen-terminated methyl silicone oils of different viscosities were added to the basic formula of liquid glue to discuss their effects on the mechanical properties of liquid glue. As the viscosity of hydrogen-terminated methyl silicone oil increases, the elongation at break and tear strength of the liquid glue gradually increase, while the tensile strength and Shore A hardness gradually decrease. This can be explained by the fact that as the viscosity of hydrogen-terminated methyl silicone oil increases, that is, the molecular chain grows, the molar mass of vinyl silicone oil increases after reacting with vinyl-terminated silicone oil. When cross-linking with multi-hydrogen-containing silicone oil, the molecular The increase in chain increases the elongation at break and decreases the tensile strength and hardness.
