Teardrops n Tiny Travel Trailers

Ok since bedsheets can be made either with cotton or polyester what type would be best suited for PMF?

I believe most everything I've read has mentioned cotton/canvas.
I did wonder whether one could perhaps do polyurethane varnish and polyester, but then I thought over here in Oz at least, one would be getting into the same level of costs as fibreglass cloth and epoxy.