Hunting for a name of a plastic found at the yard

A while back I found this plastic? I guess where one side is shiny and the other is rough. The rough side will absorb paint like a sponge. Spray it with a spray can then put latex right over it before the spray paint has had a chance to dry, it don’t matter. It will get sucked up like a sponge. Would anyone know the name of this? I’m using it for a project and I’m geeking out over how well it handles paint and would like to get some more.

Sound like expanded PVC to me.

Thanks, it’s neat stuff.