Sponge does not belong to foam plastics
Sponges are biological, living in oceans and fresh water. Sponges are just a generic term for them.
There is a similarity between them, but the process is different and the uses are different.
Foam plastic is a kind of macromolecule material which is formed by a large amount of microporous gas dispersed in solid plastic.
Sponges commonly used are made of wood cellulose fibers or foam plastic polymers. In addition, there are natural sponges made of sponges.
