Temperature -20 ~ 250 ° C (-4 ~ +482 ° F), allowing sudden cold and heat, or alternating hot and cold operation.
Pressure -0.1～6.4Mpa (Full vacuum to 64kgf/cm2)
It has solved many problems in the fields of chemical industry, petroleum and pharmaceutical industry in China. PTFE seals, gaskets, shims. Polytetrafluoroethylene seals, gaskets, sealing gaskets is the choice of suspension polymerization of polytetrafluoroethylene resin molding process made. Polytetrafluoroethylene compared with other plastics with chemical resistance, it has been widely used as a sealing material and filler material.
Used as engineering plastics, can be made of PTFE tubes, rods, bands, plates, films, etc.. Generally used in high performance requirements of corrosion-resistant pipes, containers, pumps, valves and system radar, high-frequency communication equipment, radio equipment. The dispersed liquid can be used as insulation impregnating liquid of various materials and anticorrosive layer on the surface of metal, glass and pottery. Various kinds of PTFE rings, PTFE gaskets, PTFE packing, etc. are widely used in all kinds of anticorrosive pipeline flange sealing. In addition, it can also be used for drawing silk, PTFE fiber - fluorine (foreign commodity name Teflon).
At present, all kinds of PTFE products have been in the chemical industry, machinery, electronics, electrical appliances, military, aerospace, environmental protection and bridges and other areas of the national economy has played a pivotal role.
Polytetrafluoroethylene (PTFE) use conditions industry chemical, petrochemical, oil refining, chlor-alkali, acid, phosphate fertilizer, pharmaceutical, pesticide, chemical fiber, dyeing, coking, gas, organic synthesis, non-ferrous smelting, iron and steel, atomic energy and polymer filtration materials, high purity products (such as ionic membrane electrolysis), viscous materials, transportation and operation of highly stringent hygiene requirements for the processing of food, beverages and other production sectors. The industry has been in the forefront of the development of the industry in the past few years.
Edit the advantages of the use of this paragraph
High temperature - the use of working temperature up to 250 ℃.
Low temperature resistance - with good mechanical toughness; even if the temperature drops to -196 ℃, can maintain 5% elongation.
Corrosion resistance - to most chemicals and solvents, showing inertia, resistance to strong acids and alkalis, water and a variety of organic solvents.
Climate resistance - has the best aging life among plastics.
High lubricity - has the lowest coefficient of friction of any solid material.
Non-adhesive - has the lowest surface tension of any solid material and does not adhere to anything.
Non-toxic - physiologically inert, as artificial blood vessels and organs long-term implantation without adverse reactions.
Polytetrafluoroethylene relative molecular mass is large, the low hundreds of thousands, high up to more than 10 million, generally millions (degree of polymerization in the 104 order of magnitude, while polyethylene is only 103). General crystallinity of 90 ~ 95%, melting temperature of 327 ~ 342 ℃. Polytetrafluoroethylene molecule CF2 unit arranged in a sawtooth shape, due to the fluorine atom radius is slightly larger than the hydrogen, so adjacent CF2 unit can not be completely according to the trans cross orientation, but the formation of a helical twisted chain, fluorine atoms cover almost the entire surface of the polymer chain. This molecular structure explains the various properties of PTFE. At temperatures below 19 degrees Celsius, a 13/6 helix is formed; a phase transition occurs at 19 degrees Celsius, where the molecule unravels slightly to form a 15/7 helix.
Although in perfluorocarbon compounds in the carbon-carbon bond and carbon-fluorine bond breaking need to absorb energy 346.94 and 484.88kJ/mol, but polytetrafluoroethylene depolymerization to generate 1 mol tetrafluoroethylene requires only 171.38kJ of energy.
So in the high temperature cleavage, polytetrafluoroethylene is mainly decomposition to tetrafluoroethylene. Polytetrafluoroethylene at 260, 370 and 420 ℃ weight loss rate (%) per hour were 1 × 10-4, 4 × 10-3 and 9 × 10-2, respectively, it can be seen, polytetrafluoroethylene can be used for a long time at 260 ℃. Due to the high temperature cracking also produces highly toxic by-products such as fluorine gas and perfluoroisobutene, so special attention should be paid to the safety protection and to prevent PTFE from contacting with open flames.
Edit Chemical Properties
Atmospheric Aging Resistance: Irradiation Resistance and Low Permeability: Long-term exposure to the atmosphere, the surface and properties remain unchanged.
Incombustibility: limited oxygen index below 90.
Acid and alkali resistance: insoluble in strong acids, alkalis and organic solvents (including magic acid, i.e., fluoroantimony sulfonic acid).
Oxidation resistance: resistant to corrosion by strong oxidizing agents.
Acidity and alkalinity: neutral.
Edit Physical Properties
Density: 2.1-2.3 g/cm?
Polytetrafluoroethylene has soft mechanical properties. Has very low surface energy.
Polytetrafluoroethylene (F4, PTFE) has a series of excellent performance: high temperature resistance - long-term use of 200 ~ 260 degrees, low temperature resistance - still soft at -100 degrees; corrosion resistance - resistant to aqua regia and all organic solvents; weather resistance The best aging life among plastics; high lubrication - with the smallest coefficient of friction among plastics (0.04); non-sticky - with the smallest surface tension among solid materials without adhering to any substance; non-toxic - with physiological inertia; excellent electrical properties, is the ideal C-class insulating material. Ideal Class C insulating material, a thick layer of newspaper can block high voltage of 1500V; smoother than ice. PTFE materials are widely used in the defense industry, atomic energy, petroleum, radio, electric machinery, chemical industry and other important sectors. Products: polytetrafluoroethylene rods, tubing, sheets, turned sheets. Polytetrafluoroethylene is a polymer of tetrafluoroethylene. The abbreviation is PTFE, and the structure formula is Discovered in the late 1930s and put into industrial production in the 1940s. Properties Polytetrafluoroethylene relative molecular mass is large, the low hundreds of thousands, high up to more than 10 million, generally millions (polymerization degree in the 104 order of magnitude, while the polyethylene is only 103). General crystallinity of 90 ~ 95%, melting temperature of 327 ~ 342 ℃. Polytetrafluoroethylene molecule CF2 unit arranged in a sawtooth shape, due to the fluorine atom radius is slightly larger than hydrogen, so the adjacent CF2 unit can not be completely according to the trans cross orientation, but the formation of a helical twisted chain, fluorine atoms cover almost the entire surface of the polymer chain. This molecular structure explains the various properties of PTFE. At temperatures below 19 degrees Celsius, a 13/6 helix is formed; a phase transition occurs at 19 degrees Celsius, where the molecule unravels slightly to form a 15/7 helix.
Although in perfluorocarbon compounds in the carbon-carbon bond and carbon-fluorine bond breaking need to absorb energy 346.94 and 484.88kJ/mol, but polytetrafluoroethylene depolymerization to generate 1 mol tetrafluoroethylene requires only 171.38kJ of energy.
So in the high temperature cleavage, polytetrafluoroethylene mainly depolymerized into tetrafluoroethylene. Polytetrafluoroethylene at 260, 370 and 420 ℃ weight loss rate (%) per hour were 1 × 10-4, 4 × 10-3 and 9 × 10-2, respectively, it can be seen, polytetrafluoroethylene can be used for a long time at 260 ℃. Due to the high temperature cracking also produces highly toxic by-products of fluorine gas and perfluoroisobutene, so special attention should be paid to the safety protection and to prevent polytetrafluoroethylene from contacting with open flames.
Mechanical properties
Its coefficient of friction is very small, only 1/5 of that of polyethylene, which is an important feature of perfluorocarbon surface. Also due to the extremely low intermolecular forces of fluorine-carbon chains, PTFE is non-sticky.
Polytetrafluoroethylene in -196 ~ 260 ℃ a wide range of temperatures are to maintain excellent mechanical properties, perfluorocarbon polymer is characterized by one of the low temperature is not brittle.
Chemical resistance and weather resistance
Except for molten alkali metals, PTFE is not subject to corrosion by almost any chemical reagent. For example, in concentrated sulfuric acid, nitric acid, hydrochloric acid, and even boiled in aqua regia, its weight and properties are unchanged, and almost insoluble in all solvents, only slightly soluble in all-alkanes at 300 ℃ or more (about 0.1g/100g). 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
Polytetrafluoroethylene has a low dielectric constant and dielectric loss over a wide frequency range, as well as a high breakdown voltage, volume resistivity and arc resistance.
Radiation resistance
Polytetrafluoroethylene radiation resistance is poor (104 rads), by high-energy radiation caused by the degradation of the polymer's electrical and mechanical properties are significantly reduced.
Polymerization
Polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene. Industrial polymerization reaction is carried out in the presence of a large number of water stirring, to disperse the reaction heat, and easy to control the temperature. Polymerization is generally carried out at 40 ~ 80 ℃, 3 ~ 26 kg force / cm 2 pressure, can be used inorganic persulfate, organic peroxide as an initiator, you can also use redox initiation system. Each mole of tetrafluoroethylene polymerization exothermic 171.38 kJ. Dispersive polymerization should add perfluorinated surfactants, such as perfluorooctanoic acid or its salts.
Expansion coefficient
(25～250℃)10～12×10-5/℃
Edit Summary of molding methods of PTFE products
1. Molding method
Polytetrafluoroethylene Mechanical Properties
2. Push-pressing method
3. Skin capsule method
4. Spraying method
5. Weaving method
6. Winding method
7. Rolling method
8. Extruding method
9. Adhesion method
10. Welding method
11. Heat-setting method
12. Machining method
Editorial section of the polytetrafluoroethylene sintering process
Molding shrinkage: 3.1-5.0%
Molding temperature: 330-380 degrees Celsius
Sintering conditions: It is best that the temperature does not exceed 385 degrees, otherwise the molecules will be necrotic, affecting the quality.
Material properties
Long-term use temperature -200--260 degrees, excellent chemical resistance, corrosion resistance to all chemicals, the lowest coefficient of friction in plastics,
Polytetrafluoroethylene weather resistance
There is also a very good electrical properties, its electrical insulation is not affected by the temperature, there is a "King of Plastic "
Polytetrafluoroethylene is weather resistant.
2.
Transparent or translucent state, the higher the crystallinity, the worse the transparency. Raw materials are mostly powdered resin or concentrated dispersion, with very high molecular weight, for high crystallinity thermoplastic polymers.
3.
Suitable for the production of corrosion-resistant parts, abrasion-resistant parts, seals, insulating parts and medical equipment parts1 K)
4.
Molding properties
1. Crystalline material, small moisture absorption.
2. Poor fluidity, very easy to decompose, decomposition of corrosive gases. It is desirable to strictly control the molding temperature, the mold should be heated, pouring system on the material flow resistance
Polytetrafluoroethylene vinyl tubing
should be small.
3. Powdered resin is often molded by powder powder metallurgy, using sintering method. Sintering temperature 360-375 degrees, not more than 410 degrees. Emulsion resin is usually processed by cold extrusion and then sintering process, can be formed on the surface of the article anticorrosion layer. If you need to require the transparency of the product, good toughness, should be taken to rapid cooling. Can also take extrusion molding, can be extruded tube, bar, profile.
4. PTFE melt viscosity is very high, the bulk viscosity with the increase in shear stress and decrease, showing its non-Newtonian fluid properties.
5. Secondary processing, can be hot-pressing composite, welding, bonding, reinforcing, machining, etc., in order to produce the final product.
6. It is best to use the curve sintering the first step at 120 degrees for drying
The second step such as filled graphite or diametralized ink at 250 degrees to be temperature processed.
3. The third step at 345 degrees to be processed once
4. The fourth step at 375 degrees to be processed
5. The fifth step to cool down the temperature should not be too fast
Edit this section of the polytetrafluoroethylene applications
Polytetrafluoroethylene can be molded by compression or extrusion process; can also be made into a water-dispersed liquid, used for coatings, impregnation or made of fibers.
Polytetrafluoroethylene in atomic energy, national defense, aerospace, electronics, electrical, chemical, mechanical, instrumentation, instrumentation, construction, textile, metal surface treatment, pharmaceutical, medical, textile, food, metallurgy and refining and other industries are widely used as a high and low temperature, corrosion-resistant materials, insulating materials, anti-adhesive coatings and so on, so that it becomes an irreplaceable product.
Polytetrafluoroethylene (PTFE) has excellent overall performance, high temperature resistance, corrosion resistance, non-stick, self-lubricating, excellent dielectric properties, very low coefficient of friction. Used as engineering plastics, can be made of PTFE tubes, rods, bands, plates, films, etc., generally used in high performance requirements of corrosion-resistant pipes, containers, pumps, valves, and the system of radar, high-frequency communication equipment, radio equipment, and so on. PTFE in any filler that can withstand the PTFE sintering temperature, mechanical properties can be greatly improved, while maintaining the other excellent properties of PTFE. Filled with varieties of glass fibers, metals, metallized oxides, graphite, molybdenum disulfide, carbon fiber fiber, polyimide, EKONOL ... etc., abrasion resistance, the limit of PV value can be increased by 1000 times.
Teflon cloth
Polytetrafluoroethylene tubing selection of suspension polymerization of polytetrafluoroethylene resin by plunger extrusion process. In the known plastics PTFE has the best chemical resistance and dielectric properties. Polytetrafluoroethylene braided packing is a good dynamic sealing material, is made of expanded polytetrachloroethylene strip braided, with a low coefficient of friction, abrasion resistance, chemical corrosion resistance, good sealing, non-hydrolysis, no change in the hardness of the excellent performance. It is used for gasket seals and lubricating materials working in various mediums, as well as electric insulating parts, capacitor media, wire insulation, electrical instrument insulation, etc. used in various frequencies. PTFE film is suitable for capacitor media, special cable insulation, wire insulation, electrical instrumentation insulation and sealing gaskets, but also to do non-stick tape, sealing tape, mold release.
Edit the classification of polytetrafluoroethylene and its filler products
General-purpose materials
A variety of rods, tubes, sheets, films, tapes, ropes, packing, gaskets, and graphite, molybdenum disulfide, aluminum oxide, glass fibers, carbon fibers as a filler, to improve the mechanical properties of pure polytetrafluoroethylene.
Anti-corrosion class
1. Pipes and fittings: pure PTFE pipes; PTFE lined pipes; outer wrapped glass steel pipe; steel composite flanges
2. Chemical vessel lining: PTFE lined kettle; PTFE lined tanks; PTFE lined towers;
3. Heat exchangers
Polytetrafluoroethylene
4.
4. Corrugated expansion pipe
5. Valve and pump main parts
6. Steel wire reinforced full-pressure hose
7. Filter material.
Polytetrafluoroethylene membrane after longitudinal and transverse bi-directional stretching within a large number of pores, is a new material, it will be compounded with other fabrics, can be made into a solid-phase anticorrosive filtration bag of smoke or good waterproof and breathable, wind and warm rain gear sportswear, cold weather clothing, special protective clothing and lightweight tents, pharmaceutical air compressed air, all kinds of solvents, and the filtration of high-purity gas filtration of the electronics industry.
Seals
1. Static seals: laminated gaskets; sitting material belt; elastic sealing tape;
2. Dynamic seals (preparation of packing, ring seals): V-shaped sealing body - for shafts, piston rods, valves; turbine pumps within the seals; PTFE and rubber composite sealing rings; mechanical sealing ring with a Bellows retractable mechanical seal.
Bearing class
1. Filled PTFE bearings, used in food chemical paper, textile machinery
2. Porous copper impregnated fluoroplastic metal bearings, which can be used normally in high temperature and high pressure dry friction, vacuum conditions;
Polytetrafluoroethylene oxidation-resistant
3. PTFE fiber bearings of the Bearing liners made of PTFE fibers blended with glass fibers or other fibers in composite fabrics for low speeds and high loads;
4. Filled PTFE piston rings, guide rings, machine tool rails and bridge slides
Insulation class
1. Class C insulation for wires and cables;
2. Sheathing for stator and rotor lead-in tubes of double-water, internally-cooled turbo-generators and for Thermocouple sheaths;
3. Microwave insulating materials for high-frequency and ultra-high-frequency communication equipment and radar;
4. Printed-wire substrates and insulating materials for motors and transformers (including gas transformers);
5. Insulating materials for air-conditioners, electronic stoves, all kinds of heaters, and sulfur-hexafluoride circuit-breakers
Anti-sticking materials
1. PTFE glass cloth on the hot rolls of the pulping machine PTFE glass cloth cover on the hot roll of sizing machine - it can eliminate the phenomenon of sticky roll formed by chemical slurry and greatly improve the production rate and the quality of blank
Insoluble in strong acid, alkali and organic solvents
cloth quality;
2. Microwave drying conveyor belt of food industry Conveyor belts for microwave drying in the food industry - Compared with other materials, conveyor belts have the advantages of not absorbing microwave energy, non-sticky materials due to power saving and cleaning
3. Polyethylene bagging sealing of the thermal laminating set of anti-sticking materials;
4. Anti-stick coating - Used in kitchen pots and pans, baking bread baking molds, frozen food storage Tray, iron bottom, photocopier pinch rollers
Temperature-resistant class
1. Microwave oven drive transmission device, such as microwave oven couplings, rollers;
2. Various kinds of refrigeration, air-conditioning, oxygen generator, compressor temperature-resistant fittings
3. Applied in the silicone raw materials cleaning and drying of the drying oven trays, the use of the material on the surface of the trays can be avoided to avoid the silicone Raw materials and metal contact, but also play a high temperature, acid and alkali effect
Other categories
1. Human body substitute arteries, veins, blood vessels, cardiac membranes;
2. Endoscopes, forceps catheters, tracheal tubes;
3. Other tubes, vials, filters, and other medical equipment.
Types and applications of PTFE microporous membrane
1. PTFE air filtration membrane: thickness of about 0.01mm, air permeability 60-80L/m2.s, with a smooth surface, chemical resistance, air permeability and impermeable to water, air permeability, flame retardant, high temperature resistance, resistance to strong acids and alkalis, non-toxic and other characteristics, is widely used in the chemical industry, iron and steel, metallurgy, carbon black, power generation, Cement, waste incineration and other industrial furnaces, such as flue gas dedusting filtration;
2. PTFE purification filtration membrane: thickness of 0.02-0.03mm, bubble point ≥ 1kg/cm2 ( 5.3m/s 127Pa), is widely used in the field of pharmaceuticals, biochemical, microelectronics, and laboratory consumables, etc.; dust-free workshops, laboratories, ventilation equipment, purification equipment, medical and electronic Industry air purification
3. PTFE clothing film: thickness of 0.03-0.05mm or so, moisture permeability ≥ 10,000g/m2.24h, hydrostatic pressure ≧ 150kPa, widely used in sportswear, cold weather clothing, firefighting, public security, medical, biological and chemical prevention of special clothing; shoes, hats and gloves, as well as sleeping bags, tents and so on.
4. PTFE composite film: solvent-based PU is applied to the surface of PTFE microporous film by our unique process, forming a microporous film with hydrophilic and oil-repellent function. It has the characteristics of corrosion resistance, high temperature resistance, aging resistance, high precision and ultra-microfiltration. Widely used in clothing fabrics, smoke removal, purification and sterilization.