On the contrary, sponge rubber usually starts with expandable rubber types like EPDM or neoprene. The rubber compound is then supplemented by using a chemical blowing agent, which, on heating, decomposes and releases gases. This process causes the expansion of the rubber and also the formation of a sponge-like framework. https://rubber-foam-versus-sponge37148.thechapblog.com/32949199/the-single-best-strategy-to-use-for-rubber-foam-versus-sponge-rubber