Molded silicone foam products are simply made of special silicone raw materials and foaming agents.

One-time molding, a large amount of air is generated during the vulcanization process, resulting in a large number of small holes inside the silicone.

But must pay attention to the following issues.

First: The 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.


Second: Properly control the amount of vulcanizing agent and foaming agent so that the foaming speed can match 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.


Third: Proper use of vulcanizing agent can better control the pore size and density of the sponge (of course, it depends on experience deployment). Usually the combination of vulcanizing agent DBPMH and BP or TBPB and DCBP is better.


Fourth: 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.


Fifth: The foaming agent should be evenly dispersed in the rubber compound. Generally, the foaming agent particles are easy to agglomerate and difficult to disperse. The ratio of raw rubber/foaming agent masterbatch (1:1) can be made first, and then mixed to improve the dispersion effect.

Sixth: For rubber materials using molded silicone foaming technology, care should be taken to remove air bubbles in the rubber material 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 porous in the mold once to form a sponge of a certain shape and size, and the second-stage vulcanization is no longer porous; 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.


About foamed silicone, please check the details:
https://www.siliconefoam.net/product-iota-f663a,b-liquid-silicone-rubber-foam-.html