Sponge rubber is a material that has the best of both worlds as it offers similar properties to the original elastomer but offers better compression ability, and overall better cushioning. Sponge rubber and foam rubber are two different things and should not be thought of as the same. It may be easier and better to define the two different types of sponge rubber, open cell sponge rubber and closed cell sponge rubber. Sponge rubber is made by using blowing agents which are essentially chemicals that decompose when heated and create bubbles. These ‘bubbles’ become the cells within the elastomer. There are many types of sponge rubber, so in turn, there are also many specifications for cellular rubber; to list a few: MIL-R-6130 (now superseded by ASTM D6576), MIL-R-46089 (now superseded by ASTM D1056), AMS 3195, AMS 3323A, and AMS 3196. Some of the sponge specifications have been superseded, but MIL-STD-670 was cancelled, and MIL-C-3133 replaced it and used its suffixes. Later, MIL-C-3133 was superseded by ASTM D1056. These are all specifications you can get your sponge tailored to. It’s important to ensure the specification you tie your sponge to, is exactly what you’re looking for.
Closed cell Sponge rubber have ‘cells’ that are not connected with each other. This helps to prevent water absorption. These cells have gases still trapped inside them which maintains the elasticity. The closed cell structure of this sponge makes it ideal for compression and shock absorption. Closed Cell Sponge Rubber can come in a number of different sponges, including silicone sponge, fluorosilicone sponge, Buna-N Sponge, EPDM Sponge, Viton® Sponge, and Epichlorohydrin sponge.
Some popular commercial sponges are R-10490, R-10480, R-10470, R-10460, all put out by Saint Gobain Performance Plastics Corporation. NEDC can convert Closed Cell Sponge Rubber at its facility with different methods including waterjet cutting and die cutting. Closed Cell Sponge Rubber can also be laminated with NEDCs diverse line of 3M products, including acrylic and silicone tapes.
Open Cell Sponge Rubber also has ‘cells’ but these cells are interconnected and thus have poor water absorption resistance. These cells are formed from a blowing agent such as sodium bicarbonate. The interconnected cells are caused by an expansion of the blowing agents that are used to create the sponge. These gases rupture the other cells and cause them to be interconnected, like small tunnels. Open Cell Sponge Rubber can be die cut and waterjet cut. It can also be supplied laminated with 3M products including acrylic and silicone adhesives.