PTFE One Of The World's Best Materials For Corrosion Resistance

Polytetrafluoroethylene is the world's best corrosion resistance of one of the materials, so the "plastic king" reputation. It can be used in any kind of chemical medium for a long time, and its production solves many problems in China's chemical, petroleum, pharmaceutical and other fields. Teflon seals, washers, gaskets. PTFE seals, gaskets, gaskets are selected from the suspension polymerization of PTFE resin molding process. Polytetrafluoroethylene and other plastics compared with the resistance to chemical corrosion and excellent temperature characteristics, it has been widely used as a sealing material and filling materials. Polytetrafluoroethylene is a polymer of tetrafluoroethylene. English abbreviation for PTFE. Trade name "Teflon" (teflon). Reputation as "the king of plastics." The basic structure of polytetrafluoroethylene is as follows: CFB - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - PTFE is widely used in various anti - acid and organic solvents. Itself is not toxic to humans, but perfluorooctanoate (PFOA), one of the raw materials used in the production process, is thought to have carcinogenic effects.

Teflon (Teflon or PTFE), commonly known as "plastic king", the Chinese trade name "Teflon", "Teflon", "Teflon", "Teflon" and so on. It is made of polytetrafluoroethylene polymer compounds, with excellent chemical stability, corrosion resistance, sealing, high lubrication non-stick, electrical insulation and good anti-aging endurance. Can be in the temperature of + 250 ℃ to -180 ℃ long-term work, in addition to molten metal sodium and liquid fluoride, the ability of all other chemicals, boiled in the water can not afford to change.

Used as engineering plastics, can be made of PTFE tube, rod, belt, plate, film and so on. Generally used in high performance requirements of corrosion-resistant pipes, containers, pumps, valves and the system of radar, high-frequency communications equipment, radio equipment. Dispersions can be used as insulating dipping solutions for various materials and metal, glass, anti-corrosion layers on the surface of pottery. Various PTFE ring, poly PTFE gasket, PTFE packing and other widely used in various types of anti-corrosion pipe flange seal. In addition, can also be used for spinning, Teflon fiber - fluorine (foreign trade name Teflon).

At present, all kinds of PTFE products in the chemical industry, machinery, electronics, electrical appliances, military, aerospace, environmental protection and bridges and other areas of the national economy played a pivotal role.

Polytetrafluoroethylene (PTFE) conditions of use Chemical, petrochemical, oil refining, chlor-alkali, acid, phosphate, pharmaceutical, pesticide, chemical fiber, dyeing, coking, gas, organic synthesis, nonferrous smelting, steel, atomic and high purity products (Such as ion-exchange membrane electrolysis), viscous material delivery and operation, health requirements of highly stringent food, beverage and other processing production sector.

Medium hydrofluoric acid, phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, various organic acids, organic solvents, strong oxidants and other strong corrosive chemical media.

Temperature -20 ~ 250 ℃, allowing quenching and heating, or hot and cold alternating operation. -20 to 250 ° C (-4 to + 482 ° F)

Pressure -0.1 ~ 6.4Mpa (full negative pressure to 64kgf / cm2) -0.1 ~ 6.4Mpa (Full vacuum to 64kgf / cm2) high temperature - the use of working temperature up to 250 ℃.

Low temperature resistance - with good mechanical toughness; even if the temperature dropped to -196 ℃, can also maintain a 5% elongation. Corrosion resistance - for most chemicals and solvents, showing inert, strong acid and alkali resistance, water and a variety of organic solvents. Resistant to climate - the best aging life in plastics. High lubrication - the lowest coefficient of friction in solid materials.

No adhesion - is the smallest surface tension in the solid material and does not adhere to any substance.

Non-toxic - with physiological inertia, as artificial blood vessels and organs long-term implantation in the body without adverse reactions.

Polytetrafluoroethylene has a relatively high molecular weight, a low number of hundreds of thousands, a height of more than 10 million, typically millions (polymerization degree of 104 orders of magnitude, and polyethylene only at 103). General crystallinity of 90 ~ 95%, melting temperature of 327 ~ 342 ℃. The CF2 units in the polytetrafluoroethylene molecules are arranged in a zigzag shape. Since the radius of the fluorine atoms is slightly larger than that of the hydrogen, the adjacent CF2 units can not be completely cross-oriented, but form a helical twisted chain, the fluorine atoms are almost covered The entire surface of the polymer chain. This molecular structure explains the various properties of polytetrafluoroethylene. When the temperature is below 19 ° C, a 13/6 helix is formed; a phase change occurs at 19 ° C and the molecule is slightly unfastened to form a 15/7 helix.

Although the carbon-carbon bonds and carbon-fluorine bonds in the perfluorocarbons need to absorb energy 346.94 and 484.88kJ / mol, respectively, but the decomposition of polytetrafluoroethylene to produce 1mol of tetrafluoroethylene only energy 171.38kJ. So in the pyrolysis, the main depolymerization of polytetrafluoroethylene tetrafluoroethylene. The weight loss rate (%) of polytetrafluoroethylene at 260, 370 and 420 ° C is 1 × 10-4, 4 × 10-3 and 9 × 10-2, respectively. It can be seen that polytetrafluoroethylene can be used at 260 ℃ for a long time. Due to high temperature cracking also produce highly toxic byproducts Fluorocarbon and perfluoroisobutylene, etc., so pay special attention to safety protection and to prevent the exposure of Teflon open flame.

Mechanical properties of its friction coefficient is very small, only 1/5 of polyethylene, which is an important feature of perfluorocarbon surface. And because the fluorine - carbon chain between the molecular force is very low, so polytetrafluoroethylene has a non - stick.

It does not melt at a temperature of 250 ° C and is not brittle at an ultra-low temperature of -260 ° C. Polytetrafluoroethylene smooth exception, even the ice than it; it is particularly good insulation, a thick layer of thin film, it is enough to withstand the high voltage of 1500V.

Polytetrafluoroethylene in the -196 ~ 260 ℃ within a wide range of temperature to maintain excellent mechanical properties, perfluorocarbon polymer is one of the characteristics of low temperature does not brittle.

Chemical resistance and weatherability In addition to molten alkali metal, polytetrafluoroethylene is almost free from any chemical corrosion. For example, in concentrated sulfuric acid, nitric acid, hydrochloric acid, and even boiled in aqua regia, its weight and performance are unchanged, almost insoluble in all solvents, only 300 ℃ or more slightly soluble in the whole alkane (about 0.1g / 100g). Polytetrafluoroethylene does not absorb moisture, non-combustible, oxygen, UV are very stable, so it has excellent weather resistance. Electrical properties PTFE in a wide frequency range of dielectric constant and dielectric loss are very low, and the breakdown voltage, volume resistivity and arc resistance are higher.

Radiation resistance of polytetrafluoroethylene radiation resistance is poor (104 Rad), by high energy radiation caused by degradation, polymer electrical properties and mechanical properties were significantly decreased.

Polymeric polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene. The industrial polymerization is carried out in the presence of a large amount of water to disperse the reaction heat and to facilitate the control of the temperature. The polymerization is generally carried out at a pressure of 40 to 80 ° C and a pressure of 3 to 26 kgf / cm 2. The inorganic persulfate, the organic peroxide is used as an initiator, and the redox-initiating system may be used. Approximately 171.38 kJ per mole of tetrafluoroethylene polymerized. Dispersed polyesters should be added with perfluorinated surfactants such as perfluorooctanoic acid or salts thereof.

Application of PTFE can be compression or extrusion processing molding; can also be made into an aqueous dispersion for coating, impregnation or made of fiber. PTFE in the atomic energy, aerospace, electronics, electrical, chemical, mechanical, instrumentation, instrumentation, construction, textile, food and other industries are widely used as high and low temperature, corrosion-resistant materials, insulation materials, anti-stick coating.

Resistance to atmospheric aging: radiation resistance and low permeability: long-term exposure to the atmosphere, the surface and performance remain unchanged. Noncombustibility: Limited oxygen limit below 90.

Acid and alkali resistance: insoluble in strong acid, alkali and organic solvents. Antioxidant: Strong resistance to strong oxidizing agents. Acid and alkaline: neutral.

The mechanical properties of polytetrafluoroethylene are softer. Has a very low surface energy.

Polytetrafluoroethylene (F4, PTFE) has a series of excellent performance: high temperature - long-term use temperature of 200 to 260 degrees, low temperature - at -100 degrees when still soft; corrosion - resistant to water and all organic solvents; (0.04); non-sticky - with the smallest surface tension in the solid material without adhering to any substance; non-toxic - with a physical inertness; Excellent electrical performance, is the ideal C-class insulation material. PTFE materials, widely used in national defense industry, atomic energy, oil, radio, electrical machinery, chemical industry and other important sectors. Products: PTFE tetrafluoroethylene bar, pipe, sheet, turning sheet. Polytetrafluoroethylene is a polymer of tetrafluoroethylene. English abbreviation for PTFE. The structure is. The late 1930s found that the 1940s into industrial production. The nature of polytetrafluoroethylene is relatively high in molecular weight, low for hundreds of thousands, highs up to 10 million or more, typically millions (degree of polymerization at 104 orders of magnitude, and polyethylene only at 103). General crystallinity of 90 ~ 95%, melting temperature of 327 ~ 342 ℃. The CF2 units in the polytetrafluoroethylene molecules are arranged in a zigzag shape. Since the radius of the fluorine atoms is slightly larger than that of the hydrogen, the adjacent CF2 units can not be completely cross-oriented, but form a helical twisted chain, the fluorine atoms are almost covered The entire surface of the polymer chain. This molecular structure explains the various properties of polytetrafluoroethylene. When the temperature is below 19 ° C, a 13/6 helix is formed; a phase change occurs at 19 ° C and the molecule is slightly unfastened to form a 15/7 helix. Although the carbon-carbon bonds and carbon-fluorine bonds in the perfluorocarbons need to absorb energy 346.94 and 484.88kJ / mol, respectively, but the decomposition of polytetrafluoroethylene to produce 1mol of tetrafluoroethylene only energy 171.38kJ. So in the pyrolysis, the main depolymerization of polytetrafluoroethylene tetrafluoroethylene. The weight loss rate (%) of polytetrafluoroethylene at 260, 370 and 420 ° C is 1 × 10-4, 4 × 10-3 and 9 × 10-2, respectively. It can be seen that polytetrafluoroethylene can be used at 260 ℃ for a long time. Due to high temperature cracking also produce highly toxic byproducts Fluorocarbon and perfluoroisobutylene, etc., so pay special attention to safety protection and to prevent the exposure of Teflon open flame. Mechanical properties of its friction coefficient is very small, only 1/5 of polyethylene, which is an important feature of perfluorocarbon surface. And because the fluorine - carbon chain between the molecular force is very low, so polytetrafluoroethylene has a non - stick.

Polytetrafluoroethylene in the -196 ~ 260 ℃ within a wide range of temperature to maintain excellent mechanical properties, perfluorocarbon polymer is one of the characteristics of low temperature does not brittle.

Chemical resistance and weatherability In addition to molten alkali metal, polytetrafluoroethylene is almost free from any chemical corrosion. For example, in concentrated sulfuric acid, nitric acid, hydrochloric acid, and even boiled in aqua regia, its weight and performance are unchanged, almost insoluble in all solvents, only 300 ℃ or more slightly soluble in the whole alkane (about 0.1g / 100g). Polytetrafluoroethylene does not absorb moisture, non-combustible, oxygen, UV are very stable, so it has excellent weather resistance. Electrical properties PTFE in a wide frequency range of dielectric constant and dielectric loss are very low, and the breakdown voltage, volume resistivity and arc resistance are higher.

Radiation resistance of polytetrafluoroethylene radiation resistance is poor (104 Rad), by high energy radiation caused by degradation, polymer electrical properties and mechanical properties were significantly decreased.

Polymeric polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene. The industrial polymerization is carried out in the presence of a large amount of water to disperse the reaction heat and to facilitate the control of the temperature. The polymerization is generally carried out at a pressure of 40 to 80 ° C and a pressure of 3 to 26 kgf / cm 2. The inorganic persulfate, the organic peroxide is used as an initiator, and the redox-initiating system may be used. Approximately 171.38 kJ per mole of tetrafluoroethylene polymerized. Dispersed polyesters should be added with perfluorinated surfactants such as perfluorooctanoic acid or salts thereof.