you can mix fabrics in your quilting; recycling is a huge part of quilting. there are some who insist that you buy only cotton everything, thread, fabric, batting...but that is just (THEIR) choice it is certainly not a rule...and there are tons of 70's quilts from our mother's made of horrible polyester...the quilts wear like steel and last forever...there is nothing wrong with mixing textiles as long as all can be laundered together.