They return to their original state when cooled. FEP resins offer nearly all of the desirable properties of PTFE, except thermal stability. PFA fluorocarbon resins are easier to process than FEP and have higher mechanical properties at elevated temperatures. PTFE resins are supplied as granular molding powders for compression molding or ram extrusion, as powders for lubricated extrusion, and as aqueous dispersions for dip coating and impregnating. FEP and PFA resins are supplied in pellet form for melt extrusion and molding.
FEP resin is also available as an aqueous dispersion.
Outstanding characteristics of the fluoroplastics are chemical inertness, high and low-temperature stability, excellent electrical properties, and low friction. However, the resins are fairly soft and resistance to wear and creep is low. These characteristics are improved by compounding the resins with inorganic fibers or particulate materials. For example, the poor wear resistance of PTFE as a bearing material is overcome by adding glass fiber, carbon, bronze, or metallic oxide. Wear resistance is improved by as much as 1,000 times, and the friction coefficient increases only slightly.