What is sponge rubber?

Sponge rubber consists of open-cell natural rubber (NR), which has been heavily degraded during production. A distinction is made between sponge rubber, cellular rubber with a closed pore structure and sponge rubber, which is a mixture of open and closed pores. The size and structure of the cells depends largely on the mixture and the production process. Accordingly, sponge rubber can be produced with different cell structures, elasticity, density and hardness. Nowadays, production is carried out by vulcanizing presses at increasing heating pressure using 4,4′-oxybis(benzenesulfohydrazide) as a blowing agent. Sponge rubber in its typical orange color is often used to make bath sponges, mats and cushions.