Well ..., not quite. "Dacron is a trademark for a polyester fiber. Dacron is a condensation polymer obtained from ethylene glycol and terephthalic acid. It's properties include high tensile strength, high resistance to stretching, both wet and dry, and good resistance to degredation by chemical bleaches and abrasion."Originally Posted by Ed Sukach
"Mylar" is closely related to Dacron - just how close, I'm not sure. It is a PET plastic, as is Dacron. Mylar apparently is a "dacron-related" plastic in a sheet form, as opposed to fibers.
BTW ... and as an antidote for "More than one would ever WANT to know" ... I found the article - "The Case for RC, Revisited - Updating the Controversy Surrounding B&W RC Printing Papers" - by Alfred A. Blaker, Camera and Darkroom, November 1991, p 36.