Sponge Rubber

Sponge Rubber for Sealing

Gaskets seal mating surfaces. They do this by deforming under pressure to take up surface imperfections. Softer gasket materials provide more deformation, and if you’re looking for a material that deforms a lot, sponge rubber may be what you need.

Basics of Sponges

A sponge material contains a large number of holes. This makes it lighter than a sold piece of the same material and gives it the ability to hold fluids in those holes, (better-called pores.).

The properties of a sponge derive from a combination of:

  • The material – neoprene, nitrile, EPDM, and silicone are the most common
  • Pore size and distribution – more pores reduce density and larger pores hold more fluid
  • Whether pores are open or closed

Open Vs. Closed Sponge Rubber Gasket Material

If pores are interconnected in a way that lets fluid move through, the material has an open cellular structure. Washing sponges have this characteristic to hold water and release it when compressed.

Sealing/gasketing applications generally need a closed structure. Here the pores are filled with nitrogen gas generated during manufacture and are not connected. Squeezing a closed cell sponge material compresses the nitrogen, which adds to the elastic behavior of the material.

The firmness of Sponge Rubber Sealing Material

Closed-cell materials are firmer than those with an open structure. Material manufacturers typically refer to sponge rubber as being soft, medium or firm. They may also reference density with a denser material being firmer.

Using Sponger Rubber for Sealing

Solid rubber materials spread sideways when compressed. This can be a problem in sealing applications where the material will be deformed a lot. An advantage of sponge over solid rubber is that it doesn’t spread out significantly.

Sponge rubber is used for vibration damping because the cellular structure provides a form of mechanical impedance. It also makes a good shock absorber and a thermal insulator. Common sealing applications are those where an air or watertight seal are needed but pressures are low. Hatches, doors and panels are examples.

For more information, or to discuss a specific application, speak with a specialist at Hennig Gasket.