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Why does silicone get oily?


Nowadays, silicone rubber has been widely applied to a variety of fields for making silicone mold. But why silicone mold appears bleeding oil? 

This question is often asked when customers ask for help for technical guidance. There are no oils contained in the molding silicone rubber, so, the silicone mold will not bleed oil. Of course, a small amount of bleeding oil is a normal phenomenon, but we can’t ignore the problem when the silicone mold appears bleeding oil in large quantities.

This phenomenon of silicone mold appears bleeding oil may mainly relate to adding too much silicone oil or having mixed the compound silicone oil which is the compound of silicone oil and white oil in the process of making silicone mold. And the white oil is a kind of petrochemicals but not the pure silicone oil. This is a mean took by manufacturers in order to save costs of silicone mold because the price of pure silicone oil is much higher than the white mineral oil.

Here, we have to say about the difference between the pure silicone oil and un-graded silicone oil to produce the high quality silicone mold and avoid the problem of bleeding oil. Firstly, you can see with your eyes and smell with your nose directly, because the ungraded silicone oil is in a turbid liquid form and smells bad. Then, you can test it by fire. The burning point of ungraded silicone oil is 100℃, while the pure silicone oil is 320℃. Besides, you can also take the freezing point method, because the silicone oil will remain clear and transparent under temperature of -50℃.

Secondly, the reason why silicone mold appears bleeding oil may be that you add too much curing agent (catalyst) in the production of silicone mold. So, you should reduce the ratio of curing agent, otherwise, this silicone oil added in the silicone rubber is easy for bleeding oil.


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