I'm looking to bond slick synthetics like polyester and/or rayon pretty much permanently. Any suggestions or preferences?

Check at your local fabric store. They sell fabric glue, although it just looks like glue stick to me.

I have found an adhesive film for instant mending of clothing, the stuff stick like steel to fabric.

Sewing is the best for fabric, Walmart is selling a beginner sewing machine for $20. It only does a chain stictch, but it is better then glue.

So does Chap Stick. Don't want to get them confused, though.

I have had great results with Aleene's OK To Wash-it. Dries clear and remains flexible. I got it at the fabric store.

Are you gluing two pieces of fabric to each other or are you trying to cover something with fabric?

If you are gluing fabric to something else 3M Super 77 works well. If gives a tacky surface so you can work fabric around odd shaped items.

Don't know if this is what you're asking about but I've had good results with it.