Since clear silicone products are transparent, how can they turn yellow, can they still be transparent after turning yellow, and what causes clear silicone turning yellow? Is it oxidation? Normal clear silicone products will not turn yellow even after being put for several years. But sometimes, during the silicone production process, some clear silicone products that have just come out of the oven turn yellow. Why do clear silicone products turn yellow? The main reasons lie in the following aspects.
The performance of vulcanizing agent is divided into ordinary type and anti-yellowing property, and its application range has the following two aspects:
Ordinary non-yellowing vulcanizing agents are usually used in some non-exposed clear silicone products that is in dark colors or with lower color appearance requirements.
The anti-yellowing vulcanizing agent is used in clear silicone products that need to be exposed to the air, the color of the clear silicone is lighter and brighter, and the color requirements are accordingly higher. The quality of the vulcanizing agent is highly correlated with the hydrogen-containing silicone oil. The hydrogen-containing silicone oil often has a better performance when it has a hydrogen value of 1.6 or more, the acid value is below 1.
When clear silicone products are formed, the main reasons that cause the color of clear silicone turning yellow after molding are:
The mold temperature is too high;
The vulcanization time is too long;
The second time vulcanization.
Sometimes we add an anti-yellowing vulcanizing agent to the silicone rubber compound, but the clear silicone product still looks yellow after molding. It may be that the anti-yellowing ability of the raw material is too poor. The suggestion for this situation is to directly replace raw materials with poor anti-yellowing properties.
Although clear silicone products have excellent weather resistance and aging resistance. But sometimes clear silicone products that have just come out of the oven still turn yellow.
In order to avoid this situation, the vulcanizing agent should be selected according to the requirements. In the process of processing clear silicone products, the molding temperature and the vulcanization time should be strictly controlled, and the yellowing resistance of the raw material should be paid attention to.
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