The problem is when you try blending polyster or polyster/cotton blends is that they don't shrink the same as cottons. It doesn't really create a good balance for a quilt top. That being said, if you want to use them, I love the idea of the floor pillows. I have washed items that said dry clean. The biggest problem I had was that the fabric was textured & the edges raveled badly. Your samples look like they wouldn't ravel, but I would wash 1 piece & see if there is a problem with that. Also, measure the piece before you wash, so that you know what size you end up with after it comes out of the dryer. To me...this final step would be the determining factor as to whether I used them or not.