Rubber sponge is a lightweight and porous form of rubber material that is often used to insulate. Silicone rubber sponge is a resilient material that is able to stand up well against abrasive temperatures and in highly compressive applications. There are two forms of silicone rubber sponge that are available on the market today: closed cell and open cell. This cellular high temperature silicone sheet, although not as resistant to high temperatures as it solid counterpart, is able to provide reliable applications that will not break or fail. Both solid silicone material and silicone rubber sponge is highly resistant to damaging environmental factors, including harsh UV rays, ozone, and oxygen.

How Do You Make a Rubber Sponge?

A rubber sponge is made by introducing gases, such as nitrogen, into the uncured liquid rubber material before it is sent through vulcanization which can be said for all sponge rubber, including silicone rubber sponge. Also known as foam rubber, this type of rubber material is characterized by its lightweight and porous structure. More specifically, it is “made from a natural or synthetic latex compounded with various ingredients and whipped into a froth…In special processes, a blowing agent is incorporated into the latex to liberate gas during vulcanization, forming small, closed cells; the resulting foam is nonabsorbent and useful for thermal insulation, as in refrigerators” (Britannica.com). Unlike solid rubber, sponge rubber is a lightweight and porous material that is generally used for insulating applications rather than protective applications. In general, there are two types of sponge rubber: closed cell and open cell. Closed cell foam will be denser with air pockets that are closely knit together whereas open cell foam will be more porous with larger air pockets. Both forms of sponge rubber are created by the introduction of gases into the uncured material; however, closed and open cell sponge rubber has slightly different manufacturing processes. Closed cell sponge rubber is generally made by “introducing a rubber compound to as gas such as nitrogen, under extreme pressure” (rubberlibrary.com). The added pressure creates a denser material that is highly moisture resistant (generally having an absorption level of less than 5%) making it ideal for sealing liquids and gases. Open cell sponge rubber is made by “introducing an inflating agent into the rubber compound which expands during vulcanization” (rubberlibrary.com). The large air pockets create an incredibly absorbent material and is ideal for applications that require a tight, such as a gasket.

What Material is Silicone Made of?

Silicone is a unique material that is made of silicone, hydrogen, oxygen, and carbon. Silicon is a chemical element that must be extracted from silica which is an abundant natural material found in most types of sand. For instance, “Also called silica sand or quartz sand, silica is made of silicon dioxide (SiO2) …Since sand is plentiful, easy to mine and relatively easy to process, it is the primary ore source of silicon” (mineralseducationcoalition.org). Manufacturing silicone starts once the silicon chemical element that is extracted from the silica material. It is then bonded “together with hydrogen and oxygen. Its structure always comprises siloxane backbone (silicon-oxygen chain) and an organic moiety bound to the silicon” (omnexus.specialchem.com). Most elastomers, both natural and synthetic, are bonded by a carbon-to-carbon polymer backbone structure; however, silicone material is bonded by a silicon-to-oxygen backbone; however, silicone material is bonded by a silicon-to-oxygen backbone structure. This unique silicon-to-oxygen polymer backbone structure gives silicone material, both solid and silicone rubber sponge, superior resistance to properties that neither natural nor synthetic rubber can match. Case in point, “As compared to organic rubber, silicone rubber has Si-O bond in its structure, and hence, it has better: heat resistance, chemical stability, electrical insulation, abrasion resistance, and weatherability as well as ozone resistance” (omnexus.specialchem.com). These excellent resistance properties of silicone material allow it to be used in highly abrasive settings and applications.

• (a) How Do You Make Silicone Foam?

  Silicone foam is made using chemical blowing agents to expand the material and make it porous and lightweight. Also known as silicone rubber sponge, they are available in two basic forms: closed cell and open cell. Closed cell silicone rubber sponge is denser of the two forms due to its manufacturing process. Closed cell silicone rubber sponge is created “by subjecting a silicone base to an inert gas at an elevated pressure, preferably after a pre-curing step, reducing the pressure to allow the base to expand to produce closed cell silicone foam and curing this expanded foam at an elevated temperature” (patents.google.com). On the other hand, open cell silicone rubber sponge is created by the addition of chemical blowing agents that are designed to expand the material without the use of pressure. Silicone rubber sponge is much less dense when compared to solid silicone material; however, they are still highly durable materials. They do have a slightly narrower operating temperature range compared to solid silicone, but silicone foam is still able to withstand temperatures of up to 426 degrees Fahrenheit (matweb.com). Additionally, silicone foam is able to remain flexible in low temperatures without becoming susceptible to embrittlement, the cracking or breaking of materials at low temperatures.

  (b) What Temperature is Silicone Good to?

  Silicone is good to temperatures as low as -103 degrees Fahrenheit and temperatures as high as +500 degrees Fahrenheit. However, silicone rubber sponge can only withstand temperatures as high as 450 degrees Fahrenheit. Despite the slight change in temperature resistance, both solid silicone and silicone rubber sponge both have wide operating temperature ranges that allow them to remain reliable materials in the face of abrasive temperatures. A high temperature silicone sheet is able to have a wide operating temperature range because “-Si-O-Si- binding energy is higher than C-C bonds” which are the bonds normally found in elastomeric backbone structures (omnexus.specialchem.com). This allows even porous silicone rubber sponge to remain flexible at low temperatures and resist embrittlement as well as remain intact in high temperatures without melting. Silicone material is able to remain flexible at low temperatures due to its low glass transition temperature which is “the temperature at which the polymer structure turns ‘viscous liquid or rubbery’” (omnexus.specialchem.com). Furthermore, silicone is able to remain a reliable material in abrasively high temperatures whether it be solid a high temperature silicone sheet or silicone rubber sponge. Silicone rubber is the idea choice in material for applications that exceed 212 degrees Fahrenheit (100 degrees Celsius) as most rubbers are not able to withstand such temperatures. Due to its wide operating temperature range, a high temperature silicone sheet is the most stable rubber material in abrasive temperatures.

Although silicone rubber sponge is a lightweight and porous material, it is still an extremely resilient material. Like solid silicone material, silicone rubber sponge is able to resist degradation caused by UV rays, ozone, and oxygen as well as abrasive temperatures ranging from -103 to 450 degrees Fahrenheit. The process of making silicone foam starts by adding foaming agents into the material allowing it to expand. Manufacturing silicone sponge is performed two different ways. Closed cell silicone rubber sponge is much denser than its open cell form due to the pressure added during its production which allows for excellent moisture resistance whereas open cell silicone does not require pressure allowing for larger air pockets. Bost a solid and a cellular high temperature silicone sheet is able to remain a reliable material for use in industrial applications; however, silicone rubber sponge is best used for compressive or insulating applications.