Influence of vinyl content and its distribution

1. The vinyl content is too low, the crosslinking density of silicone rubber is small, the hardness is low, and the tear strength is low;
2. If the vinyl content is too high, the hardness of the vulcanized rubber will increase and become brittle, and the aging resistance will decrease.

In vinyl silicone oil, the effect of terminal vinyl groups and pendant vinyl groups on the performance of LSR is also different. When vinyl silicone oil has terminal vinyl groups, the crosslinking is accompanied by molecular chain growth, and the tear resistance of silicone rubber is improved.
When contains pendant vinyl groups at the same time, the cross-linking process will not only increase the molecular chain but also increase the cross-link density and further improve the physical and mechanical properties of the vulcanizate. Therefore, by choosing different vinyl silicone oils, LSRs with different properties can be obtained, and their uses are also different.

Molar mass
Vinyl silicone oil with a small molar mass can reduce the viscosity of the rubber compound, improve the fluidity, and increase the cross-linking density of the silicone rubber to a certain extent, so that it has a certain tensile strength and hardness.
Vinyl silicone oil with large molar mass can improve the elasticity and elongation at break of silicone rubber. Using vinyl silicone oil with a wide molar mass distribution can obtain silicone rubber with excellent performance.

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