Perfluorinated Polymers

Abstract

AbstractThis article gives information on few perfluorinated polymers. Polytetrafluoroethylene (PTFE), more commonly known as Teflon®, a perfluorinated straight‐chain high polymer, has a most unique position in the plastics industry because of its chemical inertness, heat resistance, excellent electrical insulation properties, and low coefficient of friction over a wide temperature range. Commercial PTFE is manufactured by two different polymerization techniques that result in two different types of chemically identical polymer. The suspension polymerized PTFE polymer is usually fabricated by modified powder metallurgy techniques. Coagulated dispersions are processed by a cold‐extrusion process. Stabilized PTFE dispersions, made by emulsion polymerization, are processed according to latex processing techniques. The largest application of PTFE is for hookup and hookup‐type wire used in electronic equipment in the military and aerospace industries. Other electrical applications include coaxial cables, computer wire, electrical tape, electrical components, and spaghetti tubing. Seals and piston rings, basic shapes, and antistick uses constitute two‐thirds of mechanical applications. Bearing, mechanical tapes, and coated glass fabric are also produced from PTFE resins. Overbraided hose liners, thread sealant tapes, gaskets, pipe liners, fibers, and filaments are also produced. Highly porous fabric structures that can be used as membranes have been developed by exploiting the unique fibrillation capability of dispersion‐polymerized PTFE.Perfluorinated ethylene‐propylene (FEP) resin is a copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). It retains most of the desirable characteristics of polytetrafluoroethylene but with a melt viscosity low enough for conventional melt processing. As a true thermoplastic, FEP copolymer can be melt‐processed by extrusion and compression, injection and blow molding. Films can be heat bonded and sealed, vacuum‐formed, and laminated to various substrates. Chemical inertness and corrosion resistance make FEP highly suitable for chemical services; its dielectric and insulating properties favor it for electrical and electronic services; and its low frictional properties, mechanical toughness, thermal stability, and nonstick quality make it highly suitable for bearings and seals, high temperature components and nonstick surfaces. Aqueous and nonaqueous dispersion polymerizations are the most convenient routes to commercial production. The copolymer of HFP–TFE is a random copolymer; that is, HFP units add to the growing chains at random intervals. The low melt viscosity (MV) resin can be injection molded by conventional thermoplastic molding techniques. The extrusion grade is suitable for tubing, wire coating, and cable jacketing. The high MV resin is used as liners for processing equipment.Copolymers of ethylene and tetrafluoroethylene (ETFE) have been studied for more than half a century. However, modified ETFE are the products of real commercial value because they have good tensile strength, moderate stiffness, high flex life, and outstanding impact strength, abrasion resistance, and cut‐through resistance. This family of polymers can be processed by conventional methods such as melt extrusion, injection molding, transfer molding, and rotational molding. These polymers are synthesized in aqueous, nonaqueous, or mixed medium with free‐radical initiators. The general‐purpose resin is used for insulating and jacketing low voltage power wiring for mass transport system, wiring for chemical plants, and control and instrumentation wiring. It is also used to produce sockets, connectors, and switch components. These resins porvide good service in seal glands, pipe plugs, corrugated tubing, fasteners, and pump vanes.Perfluoroalkoxy (PFA) fluorocarbon resins are designed to meet industry needs in chemical, electrical, and mechanical applications. These melt‐processible copolymers contain a fluorocarbon backbone in the main chain and randomly distributed perfluorinated ether side chains. A combination of excellent chemical and mechanical properties at evevated temperatures results in reliable, high performance service to the chemical processing and related industries. These resins are produced by copolymerizing tetrafluoroethylene and perfluorovinyl ether in aqueous or nonaqueous media. PFA resins are fabricated by the conventional melt‐processing techniques used for thermoplastics. A general‐purpose grade is designed for a variety of molding and extrusion applications such as tubing, shapes, molded parts, and insulation for electrical wire and cables. Valves and fitting liners are made by a transfer‐molding process. Some grades of this polymer are suitable in semiconductor manufacturing, fluid handling systems for industry or life sciences, and instrumentation for precise measurements of fluid systems.Copolymers of tetrafluoroethylene–perfluorodioxole are perfluorinated amorphous polymers and have unusual combination of properties. These polymers, commonly known as Teflon AF, have high temperature stability, excellent chemical resistance, low surface energy, low water absorption, high limiting oxygen index, solubility at ambient temperature in fluorinated solvents, high transparency, and low refractive index. They are stiffer and have high gas permeability. The glass‐transition temperature is sensitive to polymer composition and the structure of the dioxole monomer. These polymers can be processed by various solution processing techniques such as spin coating, dip coating, spraying, or casting. Melt‐processing techniques like extrusion and injection molding are used. They are used to provide antireflective coatings, low dielectric coatings, pellicles in electronic chips, plastic optical fiber, and in gas separation membrances.