Quite the opposite, sponge rubber commonly begins with expandable rubber kinds like EPDM or neoprene. The rubber compound is then supplemented which has a chemical blowing agent, which, upon heating, decomposes and releases gases. This process contributes to the expansion in the rubber and the formation of the sponge-like construction. https://water-proofrubberfoam16173.tokka-blog.com/33916291/detailed-notes-on-water-proof-rubber-foam