There are three basic types of bowstring material (right now at least).
Polyester (dacron): B-55 or B-50 (B-500 isn't made anymore)
100% HMPE: Dynaflight '97, 8125, 8190, Mercury, Fast Flight, etc.
HMPE/Vectran blends: BCY-X, 452X, 450+, Trophy, etc.
Some materials have GORE fiber in them, but that's added for durability. It's supposed to act like an internal lubricant.
Fast Flight was the first HMPE bowstring material, invented by Bob Destin and Ray Browne (the founders of BCY) when they worked for Brownell. Brownell still owns the name, but BCY still offers the original material in their 652 Spectra.