Silica gel products become yellow after vulcanization processing method
Believe that a lot of silica gel products factory have such experience: yellow after vulcanization silicone products.
What causes the yellow after vulcanization silicone products?
Silica gel after vulcanization become yellow?
A greater number of silicone organic silicon products category, is the main chain of the molecule for Si -
Si keys for organic inorganic structure, side chain groups of both inorganic and organic properties of polymer materials.
The silica gel is divided into: high temperature vulcanization silicone, RTV type.
High temperature vulcanization silicone usually require secondary sulfide to remove oxide decomposition in the residue, is further crosslinking silicone so that to achieve better physical properties.
And secondary vulcanization silicone yellowing, transparency, a direct impact on the appearance of the product, the application scope of confined to food, health care and solar photovoltaic industries.
Cause yellowing silicone products is also different, some think it is in the production of silicone rubber raw materials and additives containing trace metal elements and NO -
3 caused by;
Some believed to be two alkyl peroxide decomposition and produce acetone, lead to alpha hydroxy butyl aldehyde condensation, dehydration, generate conjugated system caused by compound;
Also some think is silica pH influence silica gel yellowing.
Small make up is don't understand the profound academic problem, only lower the toilet after vulcanization silicone products now, so how to deal with this problem?
Silica gel products become yellow after molding, set out to solve the silica gel yellowing mainly raw rubber additives, white carbon black, considering the three aspects.
Here are several ways to improve the yellow silicone products: 1, add a resistance to yellowing of the paste 2, 5 vulcanizing agent, contains high amount of hydrogen silicone oil, silica gel resistance to yellowing effect has improved significantly, improve the transparency of the silica gel, prevent the vulcanizing agent spraying;
2, white carbon black, adding organic surface active agent to control the size of the secondary particles, the compound under the action of the agent that fight yellow, effective control of the silicone yellowing degree;
3, add a resistance to yellowing agent called pyrophosphate, without reducing mixing glue on the basis of the physical and mechanical properties of reinforced mixing adhesive ability of resistance to yellowing.