Well I tried one of these fabrics for the backing of a 24" wallhanging. I have no idea what kind of material it is. I tried burning it and couldn't tell. It didn't melt like I assume polyester would do, and it didn't burn slowly and turn to ash like I assume cotton would do. It burned quickly. Who knows?
It was kinda crinkly and stiff feeling, but not very thick. It worked wonderfully for the backing. There was no chance of tucks. It remained very flat. There was no problem quilting through it either. I wish I more of this kind of material for wallhanging backs.