Importance of Post-Curing of Silicone Products

Post curing literally means “after cure”. By definition, this means that there has already been an “initial” cure. During preliminary processing, to fix the rubber into its final shape and form, the uncured compound is subjected to high temperature. Although the compound has now been transformed into a solid piece of rubber, it is not yet in a stable finished state. You need to finish the process by post-curing the rubber.
Why Post-cure Silicone Products?
After the initial cure of the silicone, by-products (volatiles) are left within as a product of the chemical reactions that have taken place. In order to drive off these by-products, Hence, it is needed to place the silicone in a static oven and post cure at high temperature for a number of hours. The time and temperature can vary but normal is 4 hours at 200°C.
PS: It is also necessary to post-cure products made from some special polymers, for example: Fluorosilicone, Fluorocarbon/Viton, Vamac, peroxide-cured EPDM,
What benefits does post curing have on the Silicone?
Several – all arising from the fact that the post cure ensures that anything in the silicone that could react as a result of being at a high temperature, has already reacted.
– The product is rendered stable in terms of reducing changes that take place in the elastomer’s physical properties due to natural ageing. As a result of post-curing, physical changes that take place during service reduce drastically.
– Postcuring also helps preventing or reducing out-gassing from Silicone Products.
If the volatiles are not removed from the rubber and then exposed to elevated temperatures with poor ventilation, we can expect a reduction in strength, elongation, compression set properties accompanied by chemical decomposition. Insufficient or poor post-cure can result in bubbling, delamination and unsightly sticky surface deposits.
– Post curing also makes the product dimensionally stable.
Although some companies avoid post-curing by adding acid scavengers in their compounds (to prevent blooming), this is not recommended.
Shore Auto Rubber Exports Pvt. Ltd. fully post-cures all the Silicone Hoses to make sure the most robust parts are fitted in your Equipment!
Hope this newsletter was interesting. Do let us know if you have any questions!