Properties and application of PTFE and other fluoropolymers

This year marks the 72nd anniversary of the discovery of polytetrafluoroethylene, plastic known as PTFE. Invented by Dr. Roy Plunkett (1910-1994), American scientist at the Jackson Laboratory in New Jersey (USA), when conducting experiments with the gases used as refrigerants refrigerators fill. It Podgrzewał coolant which is chlorodifluoromethane and received tetrafluoroethane gas, which at a pressure of about 1940 to 1960 atmospheres and the presence of peroxide (acting as a catalyst) was polytetrafluoroethylene. The polymer with unique properties proved to be one of the most interesting materials synthesized by man. Due to the difficulties they caused in the processing, it was initially not widely used. Mainly used it the armaments industry. Only in the mid 50s French engineer Mark Gregoire for the first time made use of PTFE in the household. Since then introduced to the market a whole family of extensively used materials with unique properties that contributed to the creation of hundreds of inventions relevant for many industries. These materials are available in the form of plates, rods, sleeves, tubes, tape, wire, fibers, resins and coatings, polymer emulsions, as well as additives for use in industrial and consumer solutions. 

Synthesis, leads to the strictly linear molecules with molecular weights of 1 000 000 g / mol. As a result of this process is an emulsion of the polymer in gasoline or petroleum ether, which can process into pellets or used after concentration as a means to cover a surface or adding to the lubricants, for example. Industrial processes are mostly used to obtain a PTFE is a method for suspension and emulsion. The suspension method running in the aquatic environment with the use of acid salts as emulsifiers and perfluorokarboksylowych succinic acid peroxide as the initiator receives a PTFE dispersion. The reaction proceeds in an autoclave with stirring at 55-70oC, at a pressure of 0,34-2,45 MPa. Concentration of aqueous dispersion is carried out in centrifuges, coagulation followed by the addition of electrolytes and organic solvents and leads to a powder (0.1-1 microns). In the emulsion method, carried out in an aqueous medium in a nitrogen atmosphere without emulsifiers obtained PTFE fiber. The reactions carried out in an autoclave of stainless steel, pressure wytrzymującym least 10 MPa, loaded with the following proportions of ingredients (in parts by weight): 30 - terafluoroetylen, 100 - water, 0.2 - potassium persulfate, 0.5 - borax. 
Unusual properties of PTFE due to its chemical structure. Polarized covalent bonds between atoms of carbon and fluorine are very strong, so that is chemically inert polytetrafluoroethylene. The PTFE particles are extremely strong binding fluoro-carbon. This strong bond between the molecules cause the polytetrafluoroethylene does not melt at very high temperatures and decomposes only above 300oC.Tetrahedral hybridization of atomic orbitals of carbon causes the formation of molecular orbital energy równocennych sp3. Occurring in the carbon chain CC bonds are the strongest homoatomowe covalent bonds (the energy of 349 kJ / mol). The binding energy of CF 488 kJ / mol are the strongest heteroatomowymi polarized covalent bonds occurring in organic compounds. With the chemical structure of polytetrafluoroethylene is resistant to extreme temperatures, both high and low.Retains plasticity at temperatures from -260 ° C to +260 ° C (very broad scope of work). Pure PTFE is completely infusible. At temperatures above 260 ° C passes from the crystalline phase to the phase condis, which is clear and quite soft - but not smooth. However, only begins to decompose at 327 ° C (begins to emit a monomer and gaseous products). Due to nietopliwość it can not be processed in a manner typical for plastics (eg, by extrusion or injection), but you need to use methods or techniques of sintering Tablet - similar to those used in ceramic materials. The fibers are often formed from a mixture of polymer pellets and oil. Other varieties of this polymer, containing next to the mayors - [-CF2-CF2-] - also polymers with hydrogen atoms, are melted and so that you can modify them using traditional methods, but they have poorer thermal properties, chemical and surface of pure PTFE. 
The most important characteristics of the PTFE surface energy is small, so it has good lubricating properties and anti-adhesive (do not stick to it no impurities), the smallest among all the sliding coefficient of technical materials, poor adhesion and very low coefficient of friction (with a value close to the ice). With the equality of static and dynamic coefficient of friction is not the phenomenon of "stick-slip (stick-slip). It is characterized by resistance to low pressure vacuum. Another important characteristic of polytetrafluoroethylene is its high chemical resistance. Practically, it does not respond or does not dissolve in anything but a concentrated hydrofluoric acid, molten alkali metals, ClF3 and F2 at elevated temperatures. It is resistant to both strong acids and bases, organic and inorganic chemicals, reagents and even such as aqua regia. It does not dissolve and does not swell in any organic solvents and plasticizers.It has excellent dielectric properties and insulation. It has excellent durability UV and weather resistant. It can be used in enclosed spaces and outdoors. Does not require any maintenance, is resistant to environmental aging. Does not absorb water, moisture, is resistant to hydrolysis and hot steam-resistant microorganisms and fungi.As a non-toxic, physiologically inert, harmless to the body, tasteless, odorless and is approved for contact with food. This includes non-combustible materials. It is tough, elastic material, but due to the fact that flows under a load of construction material is not. There is little resistance to ionizing radiation. Under his influence long break CC bonds, the polymer becomes brittle, was analyzed carbon tetrafluoride. 
Thanks to these properties is a comprehensive application, the coverage of blood in the household, through transplantation, surgery, the wires on the spacecraft. Speaking of applications, can not fail to mention the seals, insulators, sliding carpets, lubricants, parts of valves, pipe joints, machine parts, bearings, rings, lubricants, corrosion protection and anti-adhesive shields against aggressive pollution, chemical apparatus, filters, pumps and membrane reactors, protective clothing, and many others. PTFE is used chemical industry, radio engineering, food processing, refrigeration, pharmaceutical, aerospace, medicine - due to the chemical inertness and the possibility of sterilization. Although polytetrafluoroethylene has already found a ton of different applications in many industries are still being developed innovative applications and products, which are a key component of fluoropolymers. 
The leading fluoropolymer is PTFE which is increasing competition from other fluoroplastów that through appropriate domieszkom get better and better properties.Among other fluoroplastów worth mentioning polymers such as politrójfluorochloroetylen - PTFCE, poly (ethyl fluoride), poly (vinylidene fluoride) - PVDF and copolymers: poly (fluoroetylenopropylen) - FEP or copolymer of tetrafluoroethylene with hexafluoropropylene, copolymers of tetrafluoroethylene with perfluorowinylosulfonowym fluoride and its derivatives, the copolymer Ethylene Tetrafluoroethylene - ETFE polymer perfluoroalkoksylowy - PFA. 
More vivid than the PTFE is PTFCE but is about 100 ° C. The lower thermal resistance than PTFE. Cold does not dissolve in any organic solvent, elevated temperatures and dissolved in benzene, toluene, cyclohexane, carbon tetrachloride, fluorowęglowodorach. Withstand prolonged heating at 170 ° C. temperature. Has greater toughness than PTFE, slowly crystallized, has good dielectric properties, is more polar than PTFE. In trade PTFCE found in the form of gaskets, valves, insulation, film, elements of electronic devices, chemical vessels. It is used in the chemical industry, electronics, electrical engineering, aerospace technology, low temperature, mechanical engineering. 
The toughest material and having the highest mechanical strength of all currently known is Fluoropolymers PVDF. It is characterized by resistance to abrasion, weathering, ionizing radiation and ultraviolet radiation, chemical resistance to acids (except sulfuric acid), alkalis, strong oxidizers, halogens. And it is not resistant to polar solvents, and acetone, oleum and factors sulfonujących at elevated temperature.Can be easily dyed in vivid colors. Widely used in precision industries, medical, food, construction, construction material and as a lining. The main characters are commercial PVDF plates, foils, pipes, insulation of pipes, hoses, heat shrinkable, packaging, pharmaceuticals and medical instruments, chemical reagents, sealing joints, tanks and more. 
Copolymers of tetrafluoroethylene with perfluorowinylosulfonowym fluoride and its derivatives are characterized by high reactivity of side groups fluorosulfonowych.Films of these copolymers are good material for making ion exchange membranes from the group-SO3H. Thanks to its excellent conductivity and chemical resistance and heat have been employed as industrial elektroizolatorach skirt and as electrolytes in fuel cells. 
In order to improve certain traits in plastic fluoropolymer domieszkuje carbon, graphite, metals, alloys (eg bronze), fiberglass and other materials. Since the launch fluoroplastów demand for constantly increasing from year to year. It is expected that the upward trend will continue over the next year. Growth in demand for fluoropolymers is due to their higher yield compared with other plastics, very good chemical and physical properties, as well as new applications are still to be found.