Vinyl silicone oil and methyl vinyl silicone rubber (raw rubber) are prone to yellowing after being stored for a period of time, which is the result of high temperature oxidation of vinyl in the air. In addition, raw materials D4 or DMC are impure, and many impurities will also yellowing. Here are some solutions to solve the yellowing of vinyl silicone oil and raw rubber.

1. The reaction temperature should not be too high, and should not exceed 160 ℃ for general batch production.
2. The vacuum degree of the reactor must be good, not to mention the absolute pressure at least more than 99%, and nitrogen protection.
3. The quality of vinyl capping agent or ring body is better, and the Cl ion and impurity capping agent must be controlled below tens of ppm.
Water content is related to polymerization, but does not affect yellowing. H2O is equivalent to a capping agent. At most, 107 glue is mixed in the product. The lower the viscosity or the higher the vinyl content, the easier the yellowing is. The yellowing problem can be controlled by achieving the above three points. In addition, antioxidant can be added to increase the yellowing resistance.

For vinyl silicone oil, please check the details:
https://www.siliconerubbers.net/product-side-chain-type-vinyl-silicone-oil-my272.html