Silicone material foaming process: add foaming agent to the silicone rubber material, and then heat and vulcanize under pressure to make the rubber foam, and the silicone rubber sponge can be obtained. But must pay attention to the following issues.


Foam silicone material

(1) A foaming agent whose decomposition products do not affect the heat resistance of silicone rubber should be selected. Generally, organic foaming agents such as foaming agent BN, urea, etc. are used, and their decomposition products are removed in the two-stage vulcanization.
(2) Properly control the amount of vulcanizing agent and foaming agent to match the foaming speed with the vulcanization speed. Increasing the amount of foaming agent will increase the pore size of the sponge pores and reduce the density; increasing the amount of vulcanizing agent will reduce the pore size of the sponge pores, increase the density, and produce thicker pore walls. In addition, the vulcanization temperature also has a great influence on the porosity of the sponge.
(3) Appropriate use of vulcanizing agents can better control the pore size and density of the sponge. Usually the combination of vulcanizing agent DBPMH and BP or TBPB and DCBP is better.
(4) No. 2 fumed silica or No. 2 fumed silica and precipitated silica can be used as a reinforcing agent. The plasticity value of the rubber should be strictly controlled. If the plasticity value is too large, it is easy to cause excessive expansion when the pores are formed, forming a rough open-pore structure, and even many pores are broken; if the plasticity value is too small, the pores will be insufficient and the product will be hard. It is easier to control the plasticity value of the rubber compound with weak reinforcing filler, and it is best to use the remilled rubber compound on the same day.
(5) The foaming agent should be evenly dispersed in the rubber compound. Generally, foaming agent particles are easy to agglomerate and difficult to disperse. It can be made into raw rubber/foaming agent masterbatch ratio (1:1) first, and then mixed to improve the dispersion effect.
(6) For the rubber compound using the molding process, care should be taken to remove the air bubbles in the rubber compound to prevent damage to the sponge structure. The rubber used for molding sponge products should be cut according to the mold specifications after being kneaded and produced, and a release agent should be coated on the surface to prepare for vulcanization in the mold. Talc powder is generally used as a release agent, and white carbon black can also be used. There are two methods for vulcanization of silicone rubber sponge model products: one is a one-step method, that is, the rubber material is made into a sponge of a certain shape and size in the mold once, and the second-stage vulcanization will no longer make holes; the other is a two-step method. The method is to vulcanize the rubber material in the mold for a short time to make it initially porosity and just form a layer of surface, and then put it in an oven to porosity into a certain shape and size. For sponge sheets, the vulcanization time of the former is usually 15-20 minutes, and the vulcanization time of the latter is generally within 5 minutes.


About silicone foam, please check the details:
https://www.siliconefoam.net/product-ultra-soft-silicone-iota-bf-2000-.html