What causes the discoloration of silicone tube products at high temperature?

We all encounter some discoloration of products in our daily work. The latex tube will turn white when stored at normal temperature, and the silicone tube will turn yellow when stored at high temperature. The existing problem is that the transparent silicone tube that food needs to contact appears yellowing after being put under the high temperature of 200 ℃ for 4 hours. What is the reason?

This problem may be solved by using silica gel high anti-yellowing curing agent C-15. General food-grade products have this requirement. To prevent yellowing due to secondary sulfur addition, anti-yellowing catalyst+anti-yellowing agent must be used. Both of them are indispensable, but they will make the oil pressure production a little sticky, which is a matter to be noted. Adding 2-3 percent of hydrogen-containing silicone oil according to the amount of silica gel can solve the yellowing problem, but the product may be a little brittle and sticky. You can spray a layer of silicone oil on the mold to solve the demoulding problem, In addition, the only way to bridge is to use platinum.

It is certainly a good idea to use anti-yellowing agent and anti-yellowing curing agent. However, it is also important to note whether the silica gel tube you are using is ideal or not. You cannot add too much internal release agent, zinc stearate, etc., so you should communicate with the supplier to see whether there is silicon oil containing hydrogen in it to provide anti-yellowing effect. The powder is very important. If the iron content in it is too high, it will turn yellow.

You can test it. Compare it with ordinary curing agent (without anti-yellowing agent) and curing agent with anti-yellowing agent. Pay attention not to add zinc stearate internal release agent. If it still doesn't work, it is recommended that you change to another rubber or use platinum curing agent. If there is sulfur or sulfur carrier in the environment (such as products that have just been cured with sulfur in the oven), the silicone tube will also turn yellow.