PTFE engineering plastic is polytetrafluoroethylene [PTFE, F4], which is one of the best corrosion-resistant materials in the world today, so it is known as the "King of Plastic". It can be used for a long time in any kind of chemical medium. Polytetrafluoroethylene seals, gaskets, and gaskets are made of suspended polymerized polytetrafluoroethylene resin molded and processed. Compared with other plastic, polytetrafluoroethylene has excellent chemical corrosion resistance and temperature resistance. It has been widely used as a sealing material and filling material.

PTFE Introduction

Polytetrafluoroethylene molecular formula Polytetrafluoroethylene is a polymer of tetrafluoroethylene. The English abbreviation is PTFE. The trade name is "Teflon". It is known as the "King of Plastic". The basic structure of polytetrafluoroethylene is - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 -. Polytetrafluoroethylene is widely used in various applications that require resistance to acids, alkalis and organic solvents. It is not toxic to humans, but one of the raw materials used in the production process, perfluorooctanoic acid (PFOA), is considered to be carcinogenic. Polytetrafluoroethylene (Teflon or PTFE), commonly known as the "plastic king", has Chinese trade names such as "Teflon", "Teflon", "Teflon", and "Teflon". It is a polymer compound made of tetrafluoroethylene through polymerization, with excellent chemical stability, corrosion resistance, sealing, high lubricity and non-stickiness, electrical insulation and good anti-aging resistance. It can work for a long time at temperatures between +250¡æ and -180¡æ, and can withstand all other chemicals except molten metal sodium and liquid fluorine, and will not change when boiled in aqua regia. It can be used as an engineering plastic to make polytetrafluoroethylene tubes, rods, strips, plates, films, etc. Generally used in corrosion-resistant pipes, containers, pumps, valves, radars, high-frequency communication equipment, radio equipment, etc. with high performance requirements. Dispersions can be used as insulating impregnation liquids for various materials and anti-corrosion coatings on the surfaces of metals, glass, and ceramics. Various polytetrafluoroethylene rings, polytetrafluoroethylene gaskets, polytetrafluoroethylene packings, etc. are widely used in various anti-corrosion pipeline flange seals. In addition, it can also be used for drawing, polytetrafluoroethylene fiber - fluorine (foreign trade name Teflon). At present, various polytetrafluoroethylene products have played a pivotal role in the national economy fields such as chemical industry, machinery, electronics, electrical appliances, military industry, aerospace, environmental protection and bridges. Polytetrafluoroethylene (PTFE) use conditions industry chemical industry, petrochemical industry, oil refining, chlorine alkali, acid production, phosphate fertilizer, pharmaceuticals, pesticides, chemical fiber, dyeing, coking, coal gas, organic synthesis, non-ferrous smelting, steel, atomic energy and high-purity product production (such as ion membrane electrolysis), viscous material transportation and operation, food and beverage processing and production departments with highly strict hygiene requirements. Medium hydrofluoric acid, phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, various organic acids, organic solvents, strong oxidants and other highly corrosive chemical media. Temperature -20¡«250¡æ, sudden cooling and heating, or alternating hot and cold operation is allowed. -20¡«250¡æ (-4¡«+482¡ãF) Pressure -0.1¡«6.4Mpa (Full vacuum to 64kgf/cm2) -0.1¡«6.4Mpa (Full vacuum to 64kgf/cm2) Advantages of PTFE High temperature resistance - the working temperature is up to 250¡æ. Low temperature resistance - good mechanical toughness; even if the temperature drops to -196¡æ, it can maintain an elongation of 5%. Corrosion resistance - inert to most chemicals and solvents, resistant to strong acids and alkalis, water and various organic solvents. Weather resistance - has the best aging life among plastic. High lubricity - has the lowest friction coefficient among solid materials. Non-adhesion - has the smallest surface tension among solid materials and does not adhere to any substance. Non-toxic - physiologically inert, no adverse reactions when implanted in the body as artificial blood vessels and organs for a long time. The relative molecular mass of polytetrafluoroethylene is relatively large, ranging from hundreds of thousands to more than 10 million, and generally millions (the degree of polymerization is in the order of 104, while polyethylene is only 103). The general crystallinity is 90-95%, and the melting temperature is 327-342¡ãC. The CF2 units in the polytetrafluoroethylene molecule are arranged in a zigzag shape. Since the radius of the fluorine atom is slightly larger than that of hydrogen, the adjacent CF2 units cannot be completely oriented in a trans-cross orientation, but form a helical twisted chain, and the fluorine atoms almost cover the surface of the entire polymer chain. This molecular structure explains the various properties of polytetrafluoroethylene. When the temperature is below 19¡ãC, a 13/6 helix is formed; a phase transition occurs at 19¡ãC, and the molecules are slightly untied to form a 15/7 helix. Although the breaking of carbon-carbon bonds and carbon-fluorine bonds in perfluorocarbon compounds requires the absorption of 346.94 and 484.88 kJ/mol of energy respectively, the depolymerization of polytetrafluoroethylene to generate 1 mol of tetrafluoroethylene only requires 171.38 kJ of energy. Therefore, during high-temperature cracking, polytetrafluoroethylene is mainly depolymerized into tetrafluoroethylene. The weight loss rate (%) of polytetrafluoroethylene at 260, 370 and 420¡ãC is 1¡Á10-4, 4¡Á10-3 and 9¡Á10-2 per hour respectively. It can be seen that polytetrafluoroethylene can be used for a long time at 260¡ãC. Since highly toxic by-products such as fluorophosgene and perfluoroisobutylene are also produced during high-temperature cracking, special attention should be paid to safety protection and to prevent polytetrafluoroethylene from contacting open flames. Mechanical properties Its friction coefficient is extremely small, only 1/5 of that of polyethylene, which is an important feature of the perfluorocarbon surface. Because the intermolecular force between the fluorine-carbon chain is extremely low, polytetrafluoroethylene is non-sticky. It does not melt at 250¡æ and does not become brittle at ultra-low temperatures of -260¡æ. Polytetrafluoroethylene is extremely smooth, even ice cannot compare to it; it has particularly good insulation properties, and a thin film as thick as a newspaper is enough to withstand 1500V high voltage electricity. Polytetrafluoroethylene maintains excellent mechanical properties in a wide temperature range of -196¡«260¡æ. One of the characteristics of perfluorocarbon polymers is that it does not become brittle at low temperatures. Chemical corrosion resistance and weather resistance Except for molten alkali metals, polytetrafluoroethylene is hardly corroded by any chemical reagents. For example, when boiled in concentrated sulfuric acid, nitric acid, hydrochloric acid, or even in aqua regia, its weight and properties do not change, and it is almost insoluble in all solvents. It is only slightly soluble in all alkanes (about 0.1g/100g) above 300¡æ. Polytetrafluoroethylene does not absorb moisture, is non-flammable, and is extremely stable to oxygen and ultraviolet rays, so it has excellent weather resistance. Electrical properties The dielectric constant and dielectric loss of polytetrafluoroethylene are very low in a wide frequency range, and the breakdown voltage, volume resistivity and arc resistance are all high. Radiation resistance The radiation resistance of polytetrafluoroethylene is poor (104 rads). After being exposed to high-energy radiation, it causes degradation, and the electrical and mechanical properties of the polymer are significantly reduced. Polymerized polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene. The industrial polymerization reaction is carried out by stirring in the presence of a large amount of water to disperse the heat of reaction and facilitate temperature control. The polymerization is generally carried out at 40-80¡ãC and 3-26 kgf/cm2 pressure. Inorganic persulfates and organic peroxides can be used as initiators, or redox initiation systems can be used. Each mole of tetrafluoroethylene releases 171.38 kJ of heat during polymerization. Dispersion polymerization requires the addition of perfluorinated surfactants, such as perfluorooctanoic acid or its salts. Application Polytetrafluoroethylene can be formed by compression or extrusion processing; it can also be made into an aqueous dispersion for coating, impregnation or fiber making. Polytetrafluoroethylene is widely used as high and low temperature resistant, corrosion resistant materials, insulation materials, anti-stick coatings, etc. in atomic energy, aerospace, electronics, electrical, chemical, machinery, instruments, meters, construction, textiles, food and other industries. Chemical properties Atmospheric aging resistance: radiation resistance and low permeability: long-term exposure to the atmosphere, the surface and performance remain unchanged. Non-flammability: limited oxygen index is below 90. Acid and alkali resistance: insoluble in strong acids, strong alkalis and organic solvents. Oxidation resistance: can resist corrosion from strong oxidants. Acidity and alkalinity: neutral. Physical properties The mechanical properties of polytetrafluoroethylene are relatively soft. It has very low surface energy. Polytetrafluoroethylene (F4, PTFE) has a series of excellent performances: high temperature resistance - long-term use temperature 200 ~ 260 degrees, low temperature resistance - still soft at -100 degrees; corrosion resistance - can withstand aqua regia and all organic solvents; weather resistance - the best aging life in plastic; high lubricity - has the smallest friction coefficient (0.04) in plastic; non-stickiness - has the smallest surface tension in solid materials and does not adhere to any substance; non-toxic - has physiological inertness; excellent electrical properties, is an ideal C-class insulation material. Polytetrafluoroethylene materials are widely used in important departments such as national defense, military industry, atomic energy, petroleum, radio, electric machinery, and chemical industry. Products: polytetrafluoroethylene rods, tubes, plates, and turning plates. Polytetrafluoroethylene is a polymer of tetrafluoroethylene. The English abbreviation is PTFE. The structural formula is. It was discovered in the late 1930s and put into industrial production in the 1940s. Polymerized polytetrafluoroethylene is generated by free radical polymerization of tetrafluoroethylene. Industrial polymerization reactions are carried out in the presence of a large amount of water with stirring to disperse the heat of reaction and facilitate temperature control. Polymerization is generally carried out at 40-80¡ãC and 3-26 kgf/cm2 pressure. Inorganic persulfates and organic peroxides can be used as initiators, or redox initiation systems can be used. Each mole of tetrafluoroethylene releases 171.38 kJ of heat during polymerization. Dispersion polymerization requires the addition of perfluoro surfactants, such as perfluorooctanoic acid or its salts. Expansion coefficient (25-250¡ãC) 10-12¡Á10-5/¡ãC Summary of polytetrafluoroethylene product molding methods 1. Molding method 2. Pushing method 3. Bag method 4. Spraying method 5. Weaving method 6. Winding method 7. Rolling method 8. Extrusion method 9. Bonding method 10. Welding method 11. Heat setting method 12. Machining method Polytetrafluoroethylene application Polytetrafluoroethylene can be formed by compression or extrusion; it can also be made into an aqueous dispersion for coating, impregnation or fiber making. Polytetrafluoroethylene is widely used as high and low temperature resistant, corrosion resistant materials, insulating materials, anti-stick coatings, etc. in atomic energy, national defense, aerospace, electronics, electrical, chemical, machinery, instruments, meters, construction, textiles, metal surface treatment, pharmaceuticals, medical, textiles, food, metallurgy and smelting industries, making it an irreplaceable product. Polytetrafluoroethylene has outstanding and excellent comprehensive properties, high temperature resistance, corrosion resistance, non-stick, self-lubricating, excellent dielectric properties, and very low friction coefficient. Used as engineering plastic, it can be made into polytetrafluoroethylene tubes, rods, strips, plates, films, etc. It is generally used in corrosion-resistant pipes, containers, pumps, valves, radars, high-frequency communication equipment, radio equipment, etc. with high performance requirements. Adding any filler that can withstand the sintering temperature of PTFE to PTFE can greatly improve its mechanical properties. At the same time, maintain other excellent properties of PTFE. The filling varieties include glass fiber, metal, metallized oxide, graphite, molybdenum disulfide, carbon fiber, polyimide, EKONOL, etc., and the wear resistance and the limit PV value can be increased by 1000 times. PTFE pipes are made of suspended polymerized PTFE resin through plunger extrusion. Among the known plastic, PTFE has the best chemical corrosion resistance and dielectric properties. PTFE braided packing is a good dynamic sealing material. It is woven from expanded PTFE strips. PTFE braided packing is a good dynamic sealing material. It is woven from expanded PTFE strips. It has excellent properties such as low friction coefficient, wear resistance, chemical corrosion resistance, good sealing, no hydrolysis, no hardening, etc. It is used for gaskets, seals and lubricating materials working in various media, as well as electrical insulation parts used at various frequencies. Capacitor dielectric, line insulation, electrical instrument insulation, etc. PTFE film is suitable for capacitor dielectric, insulation layer of special cables, wire insulation, electrical instrument insulation and sealing gasket, and can also be used as non-stick tape, sealing tape, and demoulding. PTFE classification and its filling products: 1. General materials Various rods, tubes, plate films, belts, ropes, packings, gaskets, and graphite, molybdenum disulfide, aluminum oxide, glass fiber, and carbon fiber are used as fillers to improve the mechanical properties of pure PTFE. 2. Anti-corrosion 1. Pipes and accessories: pure PTFE pipes; PTFE lined pipes; glass-reinforced steel pipes; steel composite flanges; 2. Chemical container linings: PTFE lined kettles; PTFE lined tanks; PTFE lined towers; 3. Heat exchangers; 4. Corrugated telescopic pipes; 5. Main components of valves and pumps; 6. Steel wire reinforced full-pressure hoses; 7. Filter materials. After being stretched in both the longitudinal and transverse directions, the polytetrafluoroethylene film has a large number of pores inside. It is a new material. By combining it with other fabrics, it can be made into smoke solid phase anti-corrosion filter bags or good waterproof, breathable, windproof and warm rain gear sportswear, cold-proof clothing, special protective clothing and light tents, pharmaceutical air compressed air, sterile filtration of various solvents and filtration of high-purity gases in the electronics industry. 3. Seals 1. Static seals: sandwich gaskets; seat belts; elastic sealing belts; 2. Dynamic seals (woven packing, annular seals): V-type seals - used for shafts, piston rods, valves; turbine pump internal seals; polytetrafluoroethylene and rubber composite sealing rings; retractable mechanical seals with bellows. 4. Load-bearing category 1. Filled PTFE bearings, used in food, chemical, papermaking, and textile machinery; 2. Porous copper impregnated fluoroplastic metal bearings, which can be used normally under high temperature, high pressure, dry friction, and vacuum conditions; 3. PTFE fiber bearings made of composite fabrics blended with PTFE fibers and glass fibers or other fibers, used for low speed and high load; 4. Filled PTFE piston rings, guide rings, machine tool guide rails, and bridge slides; 5. Insulation category: 1. Class C insulation materials for wires and cables; 2. Double water-cooled steam turbine generator stator and rotor water pipes and thermocouple sheaths; 3. Microwave insulation materials for high-frequency, ultra-high-frequency communication equipment and radars; 4. Printed circuit substrates and motor, transformer (including gas transformer) insulation materials; 5. Insulation materials for air conditioners, electronic furnaces, various heaters, and sulfur hexafluoride circuit breakers; 6. Anti-sticking category: 1. 1. Polytetrafluoroethylene glass cloth coating on the hot roller of the sizing machine - can avoid the sticking roller phenomenon caused by chemical slurry, greatly improving the production rate and the quality of the grey cloth; 2. Microwave drying conveyor belts in the food industry - compared with conveyor belts made of other materials, it does not absorb microwave energy and does not stick to objects, so it has the advantages of saving electricity and cleaning; 3. Heat-sealed anti-stick materials for polyethylene bag sealing; 4. Anti-stick coating - used for kitchen pots, baking molds for baking bread, frozen food storage trays, electric iron bases, and copier rollers; VII. Heat-resistant category: 1. Microwave oven drive transmission devices, such as microwave oven couplings and rollers; 2. Heat-resistant accessories for various refrigerators, air conditioners, oxygen generators, and compressors; VIII. Other categories: 1. Human substitute arteries, veins, and heart membranes; 2. Endoscopes, forceps catheters, and tracheas; 3. Other tubes, bottles, filter cloths, and other medical equipment. Fluoroplastic introduction: Fluoroplastic was founded in 1934, Schloffer and Scherer discovered polychlorotrifluoroethylene (PCTFE). And industrialization was achieved in 1949. China successfully developed fluoroplastic in 1958. After the 1980s, all countries increased their production capacity, and new varieties continued to emerge. There are more than 20 varieties now. The main fluoroplastic varieties are listed below: Polytetrafluoroethylene (PTFE, referred to as F4) Polyperfluoroethylene propylene (FEP, referred to as F46) Polychlorotrifluoroethylene (ECTFE, referred to as F3) Polyvinylidene fluoride (PVDF, referred to as F2) Polyvinyl fluoride (PVF, referred to as F1) Copolymer of vinylidene fluoride and chlorotrifluoroethylene (Kel-F, referred to as F2 3) Copolymer of vinylidene fluoride and tetrafluoroethylene (§æOomph, referred to as F2 4) Copolymer of vinylidene fluoride and hexafluoropropylene (vitonA, referred to as F2 6) Copolymer of chlorotrifluoroethylene and ethylene (Halar, referred to as F3 0) Copolymer of tetrafluoroethylene and ethylene (Tefzel, referred to as F4 0) Vinylidene fluoride and hexafluoroisobutylene copolymer (CM-1) Tetrafluoroethylene and perfluoroalkyl vinyl ether copolymer - Fusible polytetrafluoroethylene (PEA) Fluoroplastic represented by F4 have a series of excellent use characteristics, high temperature resistance and long-term use temperature of 160¡ãC. It is still soft at low temperature below -100¡ãC, and can resist aqua regia and all organic solvents. 1: At present, the fluoroplastic-lined corrosion-resistant pumps (large pumps) produced in China, such as: CQB fluoroplastic-driven large magnetic pump lining material, IHF fluoroplastic centrifugal pump, FZB fluoroplastic self-priming pump and fluorine-lined steel pipe, are all lined with polyperfluoroethylene propylene (FEP, referred to as F46) F46 pumps and have excellent corrosion resistance and good rigidity, and can resist impact, vibration and distortion. They have been widely used in the petroleum and chemical industries to transport corrosive liquids and gases. It can be used under the following conditions: temperature -80¡æ~+160¡æ, pressure ¡Ü16 kg/cm2, vacuum range (instantaneous, room temperature) 400mmHg column. During use, it shows its unique performance. Applications and benefits are listed as follows: (1) The performance and corrosion resistance are better than phenolic mortar, enamel products, glass-lined products and stainless steel. Especially when used in the presence of strong oxidants, the service life can be increased by one to several times compared with the above materials. In particular, they can withstand the penetration corrosion of ether media. (2) Can withstand the test of various corrosive media. Among the media that have been used in the process, there are bromine, benzene, formaldehyde, hydrochloric acid, hydrochloride, 50% sulfuric acid, 12% NaSCN, HSCN, isopropyl ether, 22% NaOH, chlorobenzene water, p-toluenesulfonic acid, 99.5% chlorine, 95~90% tert-butyl hypochlorite, 0.51% free chlorine, 11~12% chloropropanol aqueous solution (PH=2~3), chloropropanol, chloroacetone BB-dichloroisopropyl ether, dichloropropane, 100% benzene, hypochlorous acid, CCL4, etc. (3) In the presence of various corrosive media at the same time, it can be used even at around 160¡ãC. For example, 666 chlorinated liquid contains benzene (100%), hypochlorous acid, hydrochloric acid and other corrosive media, including strong organic solvents, strong oxidizing media, and strong acids. Except for F46 and F4, it is difficult to find a suitable material that can resist the corrosion of these media alternately or simultaneously. (4) There is a significant economic effect after use. 2. At present, China produces perfluorinated (fluoroplastic alloy) corrosion-resistant pumps (small pumps), such as CQB fluoroplastic driven small magnetic pumps. Fluoroplastic alloys have unparalleled corrosion resistance and mechanical strength, impact resistance, vibration resistance, distortion resistance and non-toxic decomposition. Pumps and pump accessories produced with this type of special material have the following advantages: (1) Corrosion resistance and high temperature resistance can transport corrosive media such as acids, alkalis, oxidants, etc. of any concentration (strength) without damage. (2) High mechanical strength, small size, compact structure, easy use and maintenance, smooth flow channel, high efficiency, and energy saving. 3. There are two main types of fluoroplastic pump products, one is the full fluorine (fluoroplastic alloy) type corrosion-resistant pump (this type is a small pump); the other is the full lined fluoroplastic (F46) type corrosion-resistant pump (this type is a large pump). Fluoroplastic pump is a type of pump classified by manufacturing materials in the chemical pump series. Fluoroplastic pumps can be divided into the following categories according to their structure: 1. Fluoroplastic centrifugal pump, 2. Fluoroplastic submersible pump, 3. Fluoroplastic magnetic pump, 4. Fluoroplastic self-priming pump, 5. Fluoroplastic pipeline pump, hexafluoroplastic mortar pump, 7. Steel-lined fluoroplastic pump, etc. Fluoroplastic pumps are widely used in: chemical, acid, alkali, smelting, rare earth, pesticides, dyes, medicine, papermaking, electroplating, pickling, radio, chemical foil and other industries to transport corrosive media such as acids, alkalis, organic solvents, strong oxidants, etc. Applicable temperature: -20¡ãC to 120¡ãC. I Fluorine-lined pumps (fluoroplastic material) are suitable for conveying any acidic and alkaline corrosive media. Fluorine-lined pumps are classified by image. At present, the fluoroplastic pumps produced by Chinese manufacturers mainly include: IHF fluoroplastic chemical pumps, FSB fluoroplastic chemical pumps, CQB fluoroplastic magnetic pumps, IMD fluoroplastic magnetic pumps, FZB fluoroplastic self-priming pumps, etc. These fluoroplastic pumps are widely used in chemical, metallurgical, pharmaceutical, chemical foil and other industries, and have important uses. Uses: Fluorine plastic pumps are widely used in: corrosive medium transportation in chemical production, chlorine water wastewater treatment and acid addition process in ion membrane caustic soda projects, electrolyte transportation in non-ferrous metal smelting, pickling process in automobile manufacturing, and pharmaceutical, petroleum, electroplating, dyes, pesticides, papermaking, food and other industries. They can convey strong corrosive media such as sulfuric acid, hydrochloric acid, hydrofluoric acid, nitric acid, aqua regia, strong alkali, strong oxidant and other strong corrosive media of any concentration for a long time under the temperature conditions of -20¡æ¡«120¡æ without any damage. Features: The chemical stability of the material of fluoroplastic pumps is very good, and it can be used to fight various acids and alkalis, and can pump organic solvents.

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