Characteristics of polytetrafluoroethylene material

Polytetrafluoroethylene (PTFE) is widely used in industries such as chemicals, petroleum, textiles, electronics, medicine, and machinery, thanks to its excellent resistance to high and low temperatures and chemical stability, good electrical insulation properties, non-stick characteristics, weather resistance, flame retardancy, and good self-lubricating properties. Among fluoroplastics, polytetrafluoroethylene (PTFE) has the highest consumption and the widest range of applications; it is an important type within fluoroplastics. PTFE boasts excellent resistance to high and low temperatures as well as chemical stability, good electrical insulation properties, non-stick characteristics, weather resistance, flame retardancy, and good self-lubricating properties; it is thus known as the \"king of plastics\". This material was initially developed to meet the needs of defense and cutting-edge technologies, and later its use was extended to civilian applications. Its applications span various fields in aerospace and civil industries, and it has now become an indispensable material in these areas of use. Performance characteristics of PTFE: PTFE is a polymer formed by the polymerization of tetrafluoroethylene monomers; it is a transparent or opaque waxy substance similar to PE, with a density of 2.2 g/cm3 and a water absorption rate of less than 0.01%. Its chemical structure is similar to that of PE, with the difference being that all hydrogen atoms in polyethylene are replaced by fluorine atoms. Due to the high bond energy of the C-F bond and its stable properties, it exhibits excellent resistance to chemical corrosion; it can withstand all strong acids (including aqua regia), as well as strong oxidizing agents, reducing agents, and various organic solvents, with the exception of molten alkali metals, fluorine-containing media, and sodium hydroxide at temperatures above 300°C ； The F atoms in PTFE molecules are symmetrical; the C-F bonds consist of a covalent connection between these two elements, and there are no free electrons in the molecule, which keeps the entire molecule neutral. As a result, it possesses excellent dielectric properties, and its electrical insulation characteristics remain unaffected by environmental conditions or frequency. Its volume resistivity is greater than 1017 Ω·m; it has low dielectric loss, a high breakdown voltage, and good arc resistance, allowing it to operate for extended periods in electrical environments at 250°C ； Due to the absence of hydrogen bonds in its molecular structure and its symmetrical design, PTFE has a very high degree of crystallinity (typically 55%–75%, sometimes as high as 94%), which gives it excellent heat resistance. Its melting point is 324°C, its decomposition temperature is 415°C, its maximum operating temperature is 250°C, its embrittlement temperature is -190°C, and its heat distortion temperature at 0.46 MPa is 120°C. PTFE possesses good mechanical properties: its tensile strength ranges from 21 to 28 MPa, its flexural strength ranges from 11 to 14 MPa, and its elongation rate is 250% to 300%. The static and dynamic friction coefficients against steel are both 0.04, which is lower than the friction coefficients of nylon, polyoxymethylene, and polyester plastics. Pure PTFE has low strength, poor wear resistance, and weak creep resistance; therefore, inorganic particles such as graphite, molybdenum disulfide, aluminum oxide, glass fibers, and carbon fibers are usually added to PTFE polymers to improve their mechanical properties ； Its damping temperature range can also be expanded and its creep resistance can be improved by blending it with other polymers such as polyphenyl ether (PHB), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and perfluoro(ethylene/propylene) copolymer (PFEP). Applications of PTFE: Its unique properties enable PTFE to be widely used in industries such as chemicals, petroleum, textiles, food processing, paper manufacturing, medicine, electronics, and machinery, as well as in marine operations. 1. Applications of corrosion resistance: Due to the shortcomings of materials such as rubber, glass, and metal alloys in terms of corrosion resistance, it is difficult for them to function in environments with harsh conditions involving high temperatures, pressures, and chemical agents; the losses resulting from this are quite significant. PTFE material, thanks to its excellent corrosion resistance, has become a key corrosion-resistant material in industries such as petroleum, chemicals, and textiles. Its specific applications include: pipelines for transporting corrosive gases, exhaust pipes, and steam pipes; high-pressure oil pipes in rolling mills; high, medium, and low-pressure pipes in aircraft hydraulic and cold-pressing systems; linings for distillation towers and heat exchangers; as well as chemical equipment such as tanks, columns, and vessels, along with valves. The quality of seals has a significant impact on the efficiency and performance of the entire machinery. The PTFE material’s properties, such as corrosion resistance, aging resistance, low friction coefficient and non-stick nature, wide temperature range, and good elasticity, make it highly suitable for manufacturing seals that require high corrosion resistance and can operate at temperatures above 100°C. Seals for groove flanges of machines, heat exchangers, high-pressure vessels, large-diameter vessels, valves, and pumps; seals for glass reaction kettles, flat flanges, and large-diameter flanges; seals for shafts, piston rods, valve rods, worm gear pumps, tie rods, and so on. 2. Applications of low-friction properties in terms of load handling: In some devices, the friction-prone parts cannot be lubricated with oil, such as in situations where lubricants would be dissolved by solvents and thus become ineffective, or in industries like papermaking, pharmaceuticals, food processing, and textiles where it is necessary to prevent lubricants from contaminating the products. This makes PTFE-filled materials the ideal choice for oil-free lubrication (direct load bearing) of mechanical components. This is because the friction coefficient of this material is the lowest among known solid materials. Its specific applications include bearings used in chemical equipment, papermaking machinery, and agricultural machinery, as well as piston rings, machine tool guides, and guide rings ； In civil engineering and construction, it is widely used as support sliders for bridges, tunnels, steel structure roof trusses, large-scale chemical pipelines, and storage tanks, as well as for bridge bearings and bridge turning mechanisms. 3. Applications in the electronics and electrical field: The inherent low loss and low dielectric constant of PTFE materials enable it to be used in enameled wires for micro-motors, thermocouples, control devices, etc ； PTFE film is an ideal insulating material for manufacturing capacitors, radio insulation gaskets, insulated cables, motors, and transformers; it is also one of the essential materials for electronic components in industries such as aerospace ； Oxygen sensors can be manufactured by taking advantage of the selective permeability of fluoroplastic films, which allow high permeability to oxygen while having low permeability to water vapor ； By taking advantage of the property of fluoroplastics, which exhibits polar charge displacement under high temperature and pressure, it is possible to manufacture microphones, speakers, components for robots, and more ； Utilizing its low refractive index property, optical fibers can be manufactured. 4. Applications in medicine and healthcare: PTFE foam is purely inert, possesses strong biocompatibility, does not cause rejection by the body, has no physiological side effects on humans, can be disinfected using any method, and features a multi-porous structure; as a result, it can be used in various rehabilitation solutions, including artificial blood vessels and grafts for soft tissue regeneration, as well as for surgical suturing in vascular, cardiac, general surgical, and plastic surgery applications. 5. Applications of non-stick properties: PTFE material has the lowest surface tension among solid materials, meaning it does not stick to any substances. Additionally, it possesses excellent resistance to high and low temperatures, which makes it widely used in applications requiring non-stick properties, such as in the manufacture of non-stick pans. Its anti-adhesion processes mainly include two types: installing PTFE components or sheets on the substrate, and applying a PTFE coating or paint-coated fabric combined with glass, which is then heat-shrunk onto the substrate. With the continuous advancement of material application technologies, the three major drawbacks of PTFE materials—cold flow, difficulty in welding, and difficulty in melt processing—are being gradually overcome, thereby expanding its application prospects in various fields such as optics, electronics, medicine, and oil and chemical industry for oil transportation and leakage prevention.

For things like material properties, it’s best to use Baidu to search for a manufacturer, and then check their website for more detailed information on the performance characteristics of their products

Thank you all for your explanations. We use polytetrafluoroethylene mainly in air valves, piston rings, and sealing rings, but we know very little about the properties of this material. Thank you for your guidance

Polytetrafluoroethylene (PTFE) is widely used in industries such as chemicals, petroleum, textiles, electronics, medicine, and machinery, thanks to its excellent resistance to high and low temperatures and chemical stability, good electrical insulation properties, non-stick characteristics, weather resistance, flame retardancy, and good self-lubricating properties.

I only know it’s widely used! Heat-resistant! The material used in non-stick pans in the past!

Our research group uses polytetrafluoroethylene as an anti-friction material

Polytetrafluoroethylene has the lowest coefficient of friction and absorbs almost no water； It boasts excellent corrosion resistance, capable of withstanding corrosion from corrosive agents such as boiling hydrochloric acid, sulfuric acid, nitric acid, and aqua regia. It can be reinforced with materials such as glass fiber powder, graphite, and molybdenum disulfide to improve its load-bearing capacity and stiffness. It is widely used in chemical manufacturing as a component in various chemical equipment, such as seals and diaphragms for chemical diaphragm valves ； It can also be used to manufacture dry-friction components that operate under high-temperature conditions or in corrosive media, such as oil-free lubricated piston rings, seals, bearings, etc. The mechanical properties of polytetrafluoroethylene are relatively soft. It has a very low surface energy and mechanical properties; its coefficient of friction is extremely low, at only 1/5 that of polyethylene, which is an important characteristic of perfluorocarbon surfaces. Furthermore, due to the extremely low intermolecular forces in fluorocarbon chains, polytetrafluoroethylene is non-stick. It does not melt at 250°C, nor does it become brittle at ultra-low temperatures of -260°C. Polytetrafluoroethylene has an exceptionally smooth surface; even ice can’t compare to it ； It has excellent insulating properties; a thin layer as thick as newspaper is sufficient to withstand a high voltage of 1500V. Polytetrafluoroethylene maintains excellent mechanical properties over a wide temperature range of -196 to 260°C. One of the characteristics of perfluorocarbon polymers is that they do not become brittle at low temperatures. Chemical resistance and weather resistance: Apart from molten alkali metals, polytetrafluoroethylene is hardly affected by any chemical reagents. For example, when boiled in concentrated sulfuric acid, nitric acid, hydrochloric acid, or even aqua regia, its weight and properties remain unchanged; it is also practically insoluble in all solvents, being only slightly soluble in alkanes at temperatures above 300°C (about 0.1 g/100 g). Polytetrafluoroethylene does not absorb moisture, is non-flammable, and is highly stable to oxygen and ultraviolet rays, thus possessing excellent weather resistance. Electrical properties: Polytetrafluoroethylene has very low dielectric constants and dielectric losses over a wide range of frequencies, and it also features high breakdown voltage, volume resistivity, and arc resistance. Radiation resistance: Polytetrafluoroethylene has poor radiation resistance (104 rads); exposure to high-energy radiation causes degradation, leading to a significant decline in both the electrical and mechanical properties of the polymer. Polymerization: Polytetrafluoroethylene is produced by the free-radical polymerization of tetrafluoroethylene. Industrial polymerization reactions are carried out under stirring in the presence of large amounts of water, to dissipate the heat of reaction and facilitate temperature control. Polymerization generally takes place at 40–80°C and under a pressure of 3–26 kilogram-force per square centimeter. Inorganic persulfates or organic peroxides can be used as initiators, or redox initiation systems can also be employed. 171.38 kJ of heat is released per mole of tetrafluoroethylene polymerized. For dispersion polymerization, perfluorinated surfactants such as perfluorooctanoic acid or its salts must be added. In applications, polytetrafluoroethylene can be shaped through compression or extrusion ； It can also be made into a water dispersion for use in coating, impregnation, or to produce fibers. Polytetrafluoroethylene is widely used in industries such as nuclear energy, aerospace, electronics, electrical engineering, chemicals, machinery, instrumentation, construction, textiles, and food processing as a material resistant to high and low temperatures and corrosion, as an insulating material, and as an anti-adhesive coating. Chemical properties of polytetrafluoroethylene: Insulation: It is unaffected by environmental conditions or frequency; its volume resistivity can reach 1018 ohms•centimeter. It has low dielectric loss and a high breakdown voltage. Resistance to high and low temperatures: It is not greatly affected by temperature changes, with a wide operating temperature range of -190~260°C. Self-lubricating property: It has the lowest friction coefficient among plastics, making it an ideal oil-free lubrication material. Non-stick surface: No known solid material can adhere to this surface; it is a solid material with the lowest surface energy. Resistance to atmospheric aging, radiation resistance, and low permeability: Even after long-term exposure to the atmosphere, its surface and properties remain unchanged. Non-flammability: The oxygen index is below 90. Coefficient of expansion (25–250°C): 10–12×10-5/°C. The welding temperature for polytetrafluoroethylene filters is 260°C℃

High temperature resistance, self-lubricating properties, corrosion resistance – but difficult to process!