One. Vulcanizing agent
1. The performance of vulcanizing agent can be divided into ordinary type and anti-yellow type. Its application scope has the following two aspects.
2. General type non-yellow vulcanizing agent, used for some non-exposed silica gel products with dark color or low color requirement.
3. Anti-yellow vulcanizing agent should be applied to products that need to be exposed, with lighter and brighter colors and higher color requirements. The quality of vulcanizing agent is highly correlated with hydrosilicon-containing oil, and Dow Corning contains hydrosilicon-containing oil with hydrogen value of more than 1.6; Acid values below 1 are better.
Ii. In terms of process, when transparent silica gel products are formed, the color of transparent silica gel products turns yellow after forming. Main problems include:
1. The mold temperature is too high; 2. Curing time is too long; 3. After the second addition of sulfur.
The raw materials themselves are of poor quality
Sometimes we add anti-yellow vulcanizing agent in the rubber, but the transparent silica gel product still looks yellow after forming, which may be the raw material's poor anti-yellow ability. The raw material suggestion for the raw material's poor anti-yellow ability is direct refueling.
Conclusion: Although silica gel products have excellent weather resistance and aging resistance. But sometimes there's a yellowness to the silicone that's just come out of the oven. In order to avoid this situation, vulcanizing agent should be selected according to the requirements, the process should strictly control the temperature of the mold and the curing time of the product, the raw materials should pay attention to the anti-yellowing property of the raw materials.