You generally shouldn't need to unless it has a special coating or something. For piecing, you want to use a shorter stitch length than for quilting. I use a 1.8-2.0mm stitch length for piecing & a 2.8-3.0mm stitch length for quilting.

As long as you use a decent poly thread (I like Guterman 100% poly, but it sheds like crazy; Aurifil also has a good quality 100% poly thread this isn't as stiff & sheds less) that isn't too old & you are using a short stitch length, you shouldn't need to overcast the seams.

Of course, all these tips are for all poly fabrics. If you mix & match fibers, I'm not sure what to suggest because I've never had good luck with that.

I'm puzzled about which poly messes up with a hot iron. I've sewed I don't know how many shirts, tops, nightgowns out of polycotton broadcloth and batiste. I've used the hottest steam and never had a problem. I think the mix on those is 65/35 or it was. It always had more cotton than poly. I also use a blended permapressed muslin.

The old doubleknit might have made a mess. That stuff was just plain awful and a cat hair magnet.

Lycra never got pressed or ironed.

Interesting thread and comments. I, too, recognize that polyester is quite durable and does not fade. So then why do quilters shun polyester? I especially like it in black since it does not fade and I love the sheen. Why do we put so much work into cottons, knowing they are not as durable? Perhaps, too, this thread is addressing two different fabrics. There are the ones that are used in clothing (men's shirts, etc) and then the double knits that wore like iron. Double knits make wonderful utility throws, quite warm and easy care. They do snag and that probably led to their demise but they were certainly good for their lifetime. If we are talking the polys in clothing, consider the percent of poly in the piece Remember the pretty blouses that we enjoyed several years ago? Gorgeous and drapey but cold in the winter and hot in the summer. But blends are usually in men's shirts. Personally there are times I wish for more of those fabrics because of durability and colorfast. Some cottons seem terrible with fraying or linting that I question why quilters frown upon blends. Remember the generations before us who used whatever was available and we now think they are gorgeous with mismatched corners,chopped off points, etal!

Polyester fabrics make very durable quilts. My MIL made quilts for my children when they were very young. They are now all in their late 40s and early 50s and we still have them. They don't get used like they once did but still get dragged out when we need extra bedding to make up beds on the floor. they also have not lost their color and look as bright as they always did. Of course some of the seams are showing their age and need some repair but that is for another day!

My grandmother made a polyester double knit quilt in the seventies. It was tied, not quilted. The pieces were leftovers from her pant suits. It is still in use today. It has maintained it's color and has survived much abuse and washing. Just keep in mind that it is very heavy.

My tenant upstairs was trying to fix a quilt made by "someone" for her brother. The cotton sewing had given out in some places. So I sewed it up as best as I could, and she and her sister-in-law came over and helped tie it in my kitchen. They were quite pleased with it.

I knew you wonderful board members would come through for me. Thank you, Thank you.

I was just going to say that I remember seeing a polyester double knit quilt made from pants suit leftovers. It was a hoot! Especially for those of us that remember those adorable pants suits. :D