About closed cells and open cells

Sponge rubber bubbles (cells)

There are two main types of sponge bubbles (cells).

Closed cell

Closed cell has independent air bubbles and leave a core when crushed.
As a feature, it is impervious to water and air, and has excellent shock absorbency, processability, buoyancy and rigidity.
It is often used for insulation, cushioning and sound-absorbing materials.

Open cell

Continuous air bubbles are connected, soft and can be crushed significantly.
As a feature, it allows water and air to pass through and has excellent water absorbency, breathability, sound absorbency and flexibility.
As an application, it is often used for soundproofing and thermal insulation.