1. Vinyl silicone oil: Participates in crosslinking, and enhances toughness while maintaining transparency

   The molecular chain of vinyl silicone oil contains reactive vinyl groups (-CH=CH₂). In an addition-curing silicone system, it can undergo an addition reaction with hydrogen-containing silicone oil to participate in the construction of the silicone crosslinking network. In a condensation-curing silicone system, it can also be uniformly dispersed in the network through compatibility with the matrix and weak interactions.
   This mode of "crosslinking participation + uniform dispersion" can optimize the crosslink density distribution of silicone, significantly improve the toughness indicators such as elongation at break and impact strength of the material. Meanwhile, due to its excellent compatibility with the matrix, it will not cause phase separation and can fully maintain the transparency of the silicone system.
2. Dimethyl silicone oil: Only acts as a physical plasticizer, with poor toughening effect and easy bleeding

   The molecular chain of dimethyl silicone oil is inert methyl-terminated/substituted, does not participate in the crosslinking reaction of silicone, and is only dispersed in the matrix relying on physical compatibility. Its role is more like a "plasticizer" — it mainly reduces the hardness of silicone and improves surface smoothness, but has a very limited effect on improving toughness (impact resistance and tear resistance).
   More importantly, the compatibility between dimethyl silicone oil and the silicone matrix is limited. Excessive addition or long-term use may lead to bleeding, which not only causes the silicone surface to become sticky and lose luster, but also damages the transparency of the system.

Supplementary Notes

• The toughening effect of vinyl silicone oil is related to its vinyl content and molecular weight. Products with medium molecular weight (tens of thousands to over 100,000) and medium vinyl content (0.1%~1%) have the best comprehensive toughening effect in transparent silicone. Excessively high molecular weight may increase the viscosity of the system and affect processing; excessively high vinyl content may excessively increase the crosslink density and instead reduce toughness.
• If the silicone system is condensation-curing, it is recommended to add a small amount of silane coupling agent to further improve the bonding force between vinyl silicone oil and the matrix and avoid bleeding.
•