The first quilt I did 30 years ago (probable more) was done with what ever I had on hand. Why? Because I didn't know any better, no one to teach me but something I thought was interesting to try. If I remember right I used poly, cotton, and also blends in that first quilt. My daughter still has it and it's held together all this time, she washes it often (as I did when she was a child) as her children still use it to bum around the house with. But now that I have started learning the real way to quilt and the do's and dont's , I use 100% cotton. Sometimes I still wander why but if I decide to use a mixed blend I will do that for the whole quilt. Not just piece the different fabrics together. I would think that what ever fabric you choose t quilt with is OK as long as you are consistent with the type.