There are no quilt police :) Ironing temp certainly could be a problem if the fabric has polyester, but if you know that then just iron it on a cooler setting. I have a very old quilt from my great aunt that has all different kinds of fabrics ~ cotton, taffeta, and who knows what else. One of my very favorite quilts is all polyester from the 60s and 70s left over from dresses my mom and I sewed. It will never wear out although I think I may someday have to replace the backing which was a used sheet. Some quilters I am sure are purist, but I think it is up to you and your purpose.