Polytetrafluoroethylene (PTFE) is an engineered plastic Resin in the fluorocarbon group, the most commonly known of which is DuPont's trademark Teflon.   This high molecular weight resin displays outstanding chemical resistance to a remarkably wide variety of chemicals.   The only known classes of chemicals that attack PTFE are the molten alkali metals such as sodium and potassium, and halogenated chemicals like fluorine gas or chlorine trifluoride.   Other halogens and related compounds such as Freon are known to effuse at a given rate.   The chemical compatibility of PTFE, combined with its other physical characteristics, make it the ideal engineered plastic for hose applications.