What is the difference between foam rubber and sponge rubber?

Foam rubber and sponge rubber are often confused, but they are not the same material. Here is a clear comparison:

Foam Rubber vs. Sponge Rubber - Key Differences

1. Manufacturing Process

Foam Rubber

Made by whipping air or gas into a rubber compound to create an open or closed cellular structure.

Typically produced from polyurethane, latex, or EPDM foams.

Sponge Rubber

Made by adding a chemical blowing agent to solid rubber (like EPDM, neoprene, silicone), which expands during vulcanization.

Can be open-cell or closed-cell depending on formulation.

2. Cell Structure

Foam Rubber

Usually has larger, more uniform cells.

Can be open-cell (soft, breathable) or closed-cell (water-resistant).

Sponge Rubber

Usually has smaller, finer cells.

More often closed-cell, giving better sealing properties and lower water absorption.

3. Softness & Flexibility

Foam Rubber:

Generally softer, more cushiony, compresses easily.

More suitable for padding, cushions, comfort applications.

Sponge Rubber:

Slightly firmer, more controlled compression.

Better for gaskets, seals, and weatherstrips where controlled sealing is needed.

4. Water Absorption

Foam Rubber:

Open-cell foam absorbs water; closed-cell foam resists water.

Sponge Rubber:

Closed-cell sponge rubber is more water-tight; ideal for sealing doors, windows, and industrial enclosures.

5. Typical Uses

Foam Rubber

Mattresses

Cushions

Shock absorption

Packaging foam

Sound insulation

Sponge Rubber

Door and window sealing strips

Automotive and industrial gaskets

HVAC seals

EPDM sponge weatherstripping

Waterproof sealing applications

6. Materials Used

Foam Rubber: Polyurethane, latex, PE foam, some EPDM foams.

Sponge Rubber: EPDM, neoprene, silicone, nitrile - usually used where durability and sealing are required.

Simple Summary