The temperature is-20 ~ 250℃ (-4 ~+482 F), allowing sudden cooling and heating, or alternating hot and cold operation.
Pressure -0. 1 ~ 6.4 MPa (full vacuum to 64 kgf/cm2).
Its appearance has solved many problems in China's chemical, petroleum, pharmaceutical and other fields. Teflon seals, gaskets and gaskets. Teflon seals, gaskets and sealing gaskets are made of suspension polymerized Teflon resin by molding. Compared with other plastics, PTFE has the characteristics of chemical corrosion resistance and is widely used as sealing material and filling material.
Used as engineering plastics, it can be made into PTFE pipes, rods, belts, plates, films and so on. Generally used for corrosion-resistant pipes, containers, pumps, valves, radars, high-frequency communication equipment, radio equipment, etc. The dispersion can be used as an insulating impregnating solution for various materials and as an anticorrosive coating for metal, glass and ceramic surfaces. Various PTFE rings, PTFE gaskets and PTFE fillers are widely used for flange sealing of various anti-corrosion pipelines. In addition, it can also be used for spinning, PTFE fiber-Teflon (foreign trade name Teflon).
At present, all kinds of PTFE products have played an important role in chemical industry, machinery, electronics, electrical appliances, military industry, aerospace, environmental protection, bridges and other national economic fields.
Usage conditions of polytetrafluoroethylene (PTFE) industries: chemical industry, petrochemical industry, oil refining, chlor-alkali, acid making, phosphate fertilizer, pharmacy, pesticide, chemical fiber, printing and dyeing, coking, gas, organic synthesis, nonferrous smelting, steel, atomic energy and polymer filter materials, production of high-purity products (such as ionic membrane electrolysis), transportation and operation of viscous materials, and food and beverage with strict hygiene requirements.
Edit this paragraph to use the advantages.
High temperature resistance-the working temperature reaches 250℃.
Low temperature resistance-good mechanical toughness; Even if the temperature drops to-196℃, the elongation of 5% can be maintained.
Corrosion resistance-inert to most chemicals and solvents, resistant to strong acid and alkali, water and various organic solvents.
Weather resistance-has the best aging life among plastics.
High lubrication-the lowest coefficient of friction among solid materials.
Non-stick-it is the smallest surface tension in solid materials and does not stick to anything.
Non-toxic-physiological inertia, no adverse reaction after long-term implantation as artificial blood vessels and organs.
The relative molecular weight of PTFE is relatively large, ranging from hundreds of thousands to more than 10 million, usually millions (the degree of polymerization is in the order of 104, while polyethylene is only in the order of 103). Generally, the crystallinity is 90 ~ 95% and the melting temperature is 327 ~ 342℃. The CF2 units in PTFE molecules are arranged in zigzag. Because the radius of fluorine atom is slightly larger than that of hydrogen atom, adjacent CF2 units can not be completely trans-oriented, but form a spiral twisted chain, and fluorine atoms almost cover the surface of the whole polymer chain. This molecular structure explains various characteristics of PTFE. When the temperature is lower than 19℃, the 13/6 helix is formed; At 19℃, the phase transition occurs, and the molecules depolymerize slightly, forming 15/7 helix.
Although the carbon-carbon bond and fluorocarbon bond in perfluorocarbon need to absorb energy of 346.94 kj/mol and 484.88kJ/mol respectively, the depolymerization of PTFE to produce 1mol tetrafluoroethylene only needs energy of171.38 kJ. Therefore, PTFE is mainly depolymerized into tetrafluoroethylene during high temperature pyrolysis. The weight loss rates (%) of PTFE at 260℃, 370℃ and 420℃ are1×10-4.4×10-3 and 9× 10-2, respectively. It can be seen that PTFE can be used for a long time at 260℃. Because toxic by-products such as fluorophosgene and perfluoroisobutylene will be produced during pyrolysis, special attention should be paid to safety protection to prevent PTFE from contacting with open flames.
Edit the chemical properties of this paragraph.
Atmospheric aging resistance: radiation resistance and low permeability: long-term exposure to the atmosphere, the surface and performance remain unchanged.
Incombustibility: oxygen index is lower than 90.
Acid and alkali resistance: insoluble in strong acid, strong alkali and organic solvents (including magic acid, namely fluoroantimonic acid).
Oxidation resistance: it can resist the corrosion of strong oxidant.
Acidity and alkalinity: neutral.
Edit the physical properties of this paragraph.
Density: 2.1–2.3g/cm?
The mechanical properties of PTFE are soft. Has a very low surface energy.
Polytetrafluoroethylene (F4, PTFE) has a series of excellent properties: high temperature resistance-long-term use temperature of 200~260 degrees, low temperature resistance-it remains soft at-100 degrees; Corrosion resistance-resistance to aqua regia and all organic solvents; Weather resistance-the best aging life in plastics: high lubrication-the smallest friction coefficient in plastics (0.04); Non-stick-the surface tension is the smallest in solid materials, and it does not stick to anything; Non-toxic-physiologically inert; Excellent electrical properties, it is an ideal C-class insulation material, and the thick newspaper layer can block the high voltage of 1500V; Smoother than ice. PTFE materials are widely used in national defense, military industry, atomic energy, petroleum, radio, electric machinery, chemical industry and other important departments. Products: PTFE 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. The molecular weight of PTFE is relatively large, ranging from several hundred thousand to more than ten million, usually several million (the degree of polymerization is in the order of 104, while polyethylene is only in 103). Generally, the crystallinity is 90 ~ 95% and the melting temperature is 327 ~ 342℃. The CF2 units in PTFE molecules are arranged in zigzag. Because the radius of fluorine atom is slightly larger than that of hydrogen atom, adjacent CF2 units can not be completely trans-oriented, but form a spiral twisted chain, and fluorine atoms almost cover the surface of the whole polymer chain. This molecular structure explains various characteristics of PTFE. When the temperature is lower than 19℃, the 13/6 helix is formed; At 19℃, the phase transition occurs, and the molecules depolymerize slightly, forming 15/7 helix.
Although the carbon-carbon bond and fluorocarbon bond in perfluorocarbon need to absorb energy of 346.94 kj/mol and 484.88kJ/mol respectively, the depolymerization of PTFE to produce 1mol tetrafluoroethylene only needs energy of171.38 kJ. Therefore, PTFE is mainly depolymerized into tetrafluoroethylene during high temperature pyrolysis. The weight loss rates (%) of PTFE at 260℃, 370℃ and 420℃ are1×10-4.4×10-3 and 9× 10-2, respectively. It can be seen that PTFE can be used for a long time at 260℃. Because toxic by-products such as fluorophosgene and perfluoroisobutylene will be produced during pyrolysis, special attention should be paid to safety protection to prevent PTFE from contacting with open flames.
mechanical character
Its friction coefficient is very small, only 1/5 of polyethylene, which is an important feature of perfluorocarbon surface. Because the intermolecular force of fluorocarbon chain is extremely low, PTFE is not sticky.
PTFE maintains excellent mechanical properties in the wide temperature range of-196 ~ 260℃, and perfluorocarbon polymer is not brittle at low temperature.
Chemical corrosion resistance and weather resistance
PTFE is hardly corroded by any chemical agent except molten alkali metal. For example, when boiled in concentrated sulfuric acid, nitric acid, hydrochloric acid or even aqua regia, its weight and properties remain unchanged, it is almost insoluble in all solvents, and only slightly soluble in total alkanes (about 0. 1g/ 100g) above 300℃. PTFE does not absorb moisture, does not burn, and is extremely stable to oxygen and ultraviolet rays, so it has excellent weather resistance.
Electrical property
PTFE has low dielectric constant and dielectric loss in a wide frequency range, and high breakdown voltage, volume resistivity and arc resistance.
radioresistance
The radiation resistance of PTFE is poor (104 rad). After being irradiated by high energy, it will degrade, and the electrical and mechanical properties of the polymer will obviously decrease.
polymerize
Polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene. Industrial polymerization is carried out by stirring in the presence of a large amount of water to disperse the heat of reaction and promote temperature control. Polymerization is generally carried out at 40 ~ 80℃ and 3 ~ 26 kgf/cm2. Inorganic persulfate and organic peroxide can be used as initiators, and redox initiation system can also be used. The heat released per mole of tetrafluoroethylene is171.38kj. In dispersion polymerization, perfluorosurfactants, such as perfluorooctanoic acid or its salts, must be added.
dilatation coefficient
(25~250℃) 10~ 12× 10-5/℃
In this paragraph, edit the summary of the molding method of PTFE products.
1. modeling method
Mechanical properties of PTFE
2. Push method
3. Skin method
4. Spraying method
weave
6. Winding method
7. Rolling method
8. Extrusion method
9. Bonding method
10. Welding method
1 1. Heat setting method
12. Processing method
Edit the sintering process of PTFE in this section.
Molding shrinkage: 3. 1-5.0%
Molding temperature: 330-380℃
Sintering conditions: the optimum temperature should not exceed 385℃, otherwise the molecules will die and affect the quality.
materials performance
Long-term use temperature -200-260 degrees, excellent chemical resistance, corrosion resistance to all chemicals, the lowest friction coefficient among plastics,
Teflon weatherability
It also has good electrical properties, and its electrical insulation is not affected by temperature, so it is known as the "king of plastics".
2.
In a transparent or translucent state, the higher the crystallinity, the worse the transparency. The raw materials are mostly powdered resin or concentrated dispersion, with extremely high molecular weight, which is a thermoplastic polymer with high crystallinity.
3.
Suitable for manufacturing corrosion-resistant parts, wear-resistant parts, sealing parts, insulating parts and medical device parts 1 K)
4.
Formability
1. Crystalline substance with low hygroscopicity.
2. Poor fluidity, easy decomposition, and corrosive gas generated during decomposition. The molding temperature should be strictly controlled, the mold should be heated, and the resistance of the gating system to the material flow.
Polytetrafluoroethylene pipe
It should not be big.
3. Powder resin is usually formed by powder metallurgy and sintering. The sintering temperature is 360-375℃ and should not exceed 465438 00℃. Emulsion resin is usually treated by cold extrusion and sintering, which can form an anti-corrosion layer on the surface of articles. If transparency and toughness of products are required, rapid cooling should be adopted. Extrusion molding can also be used, and pipes, rods and profiles can be extruded.
Melt viscosity of 4.4. PTFE is very high, and its bulk viscosity decreases with the increase of shear stress, showing its non-Newtonian fluid characteristics.
5. Secondary processing, including hot pressing compounding, welding, bonding, strengthening, machining, etc. To make the final product.
6. The first step of curve sintering is best to dry at 120℃.
The second step, such as filling graphite or fluidized ink, should be treated at 250 degrees.
3. Step 3, treat at 345 degrees once.
4. Step 4, 375 degree treatment.
Step 5: Don't cool down too fast.
Edit PTFE application in this section.
PTFE can be formed by compression or extrusion; It can also be made into an aqueous dispersion for coating, impregnating or manufacturing fibers.
Polytetrafluoroethylene is widely used as high and low temperature resistant and corrosion resistant material, insulating material and anti-sticking coating, which is an irreplaceable product in industries such as atomic energy, national defense, aerospace, electronics, electric power, chemical industry, machinery, instruments, architecture, textile, metal surface treatment, pharmacy, medical treatment, textile, food, metallurgy, smelting and so on.
PTFE has excellent comprehensive properties, such as high temperature resistance, corrosion resistance, non-stick, self-lubrication, excellent dielectric properties and low friction coefficient. Used as engineering plastics, it can be made into PTFE pipes, rods, belts, plates, films and so on. , generally used in corrosion-resistant pipes, containers, pumps, valves, radar, high-frequency communication equipment, radio equipment, etc. By adding any filler that can withstand the sintering temperature of PTFE, the mechanical properties can be greatly improved while maintaining other excellent properties of PTFE. Filled with glass fiber, metal, metallized oxide, graphite, molybdenum disulfide, carbon fiber, polyimide, EKONOL…, etc. Wear resistance and ultimate PV value can be increased by 1000 times.
Teflon cloth
PTFE tube is made of suspension polymerized PTFE resin by plunger extrusion. Among the known plastics, PTFE has the best chemical resistance and dielectric properties. PTFE compression packing is a good dynamic sealing material, which is woven from expanded ptef. It has excellent properties such as low friction coefficient, wear resistance, chemical corrosion resistance, good sealing performance, no hydrolysis and no hardening. Gasket sealing and lubricating materials used in various media, as well as electrical insulation parts, capacitor media, wire insulation, electrical instrument insulation, etc. Used for various frequencies. PTFE film is suitable for capacitor dielectric, special cable insulation, conductor insulation, electrical instrument insulation and sealing gasket, and can also be used as non-stick tape, sealing tape and demoulding.
Edit the classification of PTFE and its filling products in this section.
General material
Various rods, tubes, sheets, belts, ropes, fillers and gaskets, as well as graphite, molybdenum disulfide, alumina, glass fiber and carbon fiber, are used as fillers to improve the mechanical properties of pure PTFE.
Anticorrosion grade
1. Pipes and fittings: pure PTFE pipes; PTFE lined pipe; Steel pipe wrapped with FRP; Steel composite flange
2. Chemical container lining: PTFE lined kettle; PTFE lined tank; PTFE lined tower;
3. Heat exchanger
polytetrafluoroethylene
4. Corrugated telescopic tube
5. Main components of valves and pumps
6. Steel wire reinforced full pressure hose
7. Filter materials.
Polytetrafluoroethylene film is a new material with a large number of pores inside after longitudinal and transverse stretching. When combined with other fabrics, it can be made into smoke and dust solid-phase anti-corrosion filter bags or rain gear sportswear, winter clothes, special protective clothing, light tents, compressed air for medicine, aseptic filtration of various solvents, and filtration of high-purity gases in electronic industry.
Sealing grade
1. Static seal: sandwich gasket; Seat belts; Elastic sealing belt;
2. Dynamic seal (packing and ring seal): V-shaped seal-used for shaft, piston rod and valve; Internal seal of turbopump; PTFE and rubber composite sealing ring; Telescopic mechanical seal with bellows.
Bearing grade
1. Filled PTFE bearings are used in food, chemical, paper and textile machinery.
2. Porous copper-impregnated fluoroplastic metal bearing can be used normally under high temperature and high pressure dry friction and vacuum conditions;
Oxidation resistance of PTFE
3. The bearing liner made of PTFE fiber mixed with glass fiber or other fibers is used for low speed and high load;
4. Fill PTFE piston ring, guide ring, machine tool guide rail and bridge slide block.
Insulation type
1. Class C insulating material for wires and cables;
2. Water diversion pipe sheaths and thermocouples of the stator and rotor of the double-water internally cooled turbogenerator;
3. Microwave insulation materials for high-frequency and ultra-high-frequency communication equipment and radar;
4 printed circuit boards and insulating materials for motors and transformers (including gas transformers);
5. Insulation materials for air conditioners, electric furnaces, various heaters and sulfur hexafluoride circuit breakers.
Anti-sticking grade
1. The hot roller of sizing machine is covered with PTFE glass cloth, which can avoid the phenomenon of roller sticking caused by chemical slurry and greatly improve the productivity and billet.
Insoluble in strong acid, strong alkali and organic solvent.
Cloth quality;
2. Microwave drying conveyor belt in food industry-Compared with conveyor belts made of other materials, it does not absorb microwave energy, so it has the advantages of saving electricity and cleaning.
3. The heat-sealed anti-sticking material is sealed in a polyethylene bag;
4. Anti-sticking coating-used for kitchen pots, baking molds for baking bread, storage trays for frozen food, bottom of electric irons and rollers of photocopiers.
Temperature tolerance grade
1. Driving transmission device of microwave oven, such as coupling and roller of microwave oven;
2. All kinds of temperature-resistant accessories for refrigerators, air conditioners, oxygen generators and compressors.
3. When the silicon raw material is cleaned and dried, it is applied to the furnace tray. When the material is laid on the surface of the tray, it can avoid the contact between silicon raw materials and metals, and also achieve the effects of high temperature resistance and acid and alkali resistance.
Other categories
1. The human body replaces arteries, veins and endocardium;
2. Endoscope, forceps catheter and trachea;
3. Other medical equipment, such as test tubes, bottles and filter cloth.
Classification and application of PTFE microporous membrane
1. PTFE air filtration membrane: the thickness is about 0.0 1mm, and the air permeability is 60-80l/m2.s. It has the characteristics of smooth surface, chemical resistance, air permeability, large air permeability, flame retardancy, high temperature resistance, strong acid and alkali resistance and non-toxicity, and is widely used in chemical industry, steel, metallurgy, carbon black, power generation and so on.
2.PTFE filtration membrane: the thickness is 0.02-0.03mm, and the bubble point is ≥1kg/cm2 (5.3m/s127pa), which is widely used in the fields of pharmacy, biochemistry, microelectronics and laboratory consumables. Air purification in dust-free workshops, laboratories, ventilation equipment, purification equipment, medical electronics and other industries
3. PTFE clothing film: the thickness is about 0.03-0.05mm, the moisture permeability is ≥ 10000g/m2.24h, and the hydrostatic pressure is ≥ 150 kpa, which is widely used in sportswear, winter clothes, fire protection, public security, medical treatment, biochemical prevention and other special clothing; Shoes and hats, gloves, sleeping bags, tents, etc.
4. PTFE composite membrane: solvent-based polyurethane is coated on the surface of PTFE microporous membrane through our unique process to form a microporous membrane with hydrophilic and oil-proof functions. It has the characteristics of corrosion resistance, high temperature resistance, aging resistance, high precision and ultra-micro filtration. Widely used in clothing fabrics, smoke and dust removal, purification and sterilization.