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For the products we often prepare for our customers at Breiner Non-Metallics, the materials we commonly work with are foam rubber and sponge rubber. Both are reliable and fill the needs of our customers. However, there are still some key differences.

The core differences between foam and sponge rubber are how they are created. Major differences in the ingredients and methods of preparation yield two very different products, each with properties that best suit them for different applications.

What’s the best material for your needs?

Foam Rubber

Foam rubber is created using two key components, a blowing agent (a gas of chemical that releases gas) and a liquid mixture, containing a cocktail of different chemical compounds such as polyols and polyisocyanates, water and other chemical additives like flame retardants.

The blowing agent forms a mass of small bubbles within the final material that helps form its properties. However, depending on the exact mixture, combination and ratio of elements of the liquid base, the exact properties of the foam rubber can change.

Foam rubber can be either rigid or flexible, based on the mixture. Flexible foam rubber is a great material for cushioning and is often found in furniture, automobile furnishings, the soles of shoes and automobile trim. Rigid foam rubber is sturdy and has strong temperature resistance, making it ideal for use in freezer and refrigeration applications.

Sponge Rubber

When it comes to sponge rubber, unlike foam rubber, there are different subcategories to consider. Sponge rubber typically breaks down into three categories: open-cell sponge rubber, closed-cell sponge rubber and silicone sponge rubber.

The preparation of sponge rubber and foam rubber is very similar. But, slight differences in the process yield very different products. Here’s what makes each different.

Open-Cell Sponge Rubber

Open-cell sponge rubber gets its name because of the chain of interconnected pockets inside the material. These are created by adding sodium bicarbonate to the heated liquid mold which creates the gaps as in sets.

The result is a dense and resilient rubber material. Open-cell foam rubber is capable of standing up to wear and tear, so it shines in applications where longevity is useful. For example, open-cell is commonly used in mousepads.

Closed-Cell Sponge Rubber

Like open-cell, closed-cell sponge rubber has gaps and pockets embedded within the material. However, these pockets are balloon-shaped, isolated and filled nitrogen gas. The pockets are formed by adding a chemical powder that decomposes under heat and pressure.

Open-cell sponge rubber is often seen in sheets and rolls and its density makes it ideal of outdoor applications. Outdoor electrical outlets, weather-stripping, thermal insulation and industrial padding all commonly use this kind of rubber.

Silicone Sponge Rubber

The final kind of sponge rubber, silicone is created by heat curing the gum-based polydimethylsiloxane which expands to create a structure similar to closed-cell sponge rubber, but much softer and more compliant.

Silicone is perhaps one of the most well-known rubber materials, and for good reason. This material is useful in a wide range of applications, especially its use in rough conditions and conditions with extreme temperatures.

Unsure of which material best suits your needs? Visit our materials selection guide or give us a call. We are happy to help!