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PTFE (Teflon) features


发布时间:2010年7月23日  阅读次数:5730    

PTFE

Teflon PTFE Chinese name, English name Poly tetra fluoro ethylene ptfe emulsion is a kind of chemical material with PTFE, it is widely used in packaging, electronic and electrical, chemical energy, corrosion-resistant materials, Teflon high Performance of special coating is a PTFE-based fluorine resin coating, the English name for Teflon, for the sake of pronunciation, commonly known as Teflon, iron, Teflon, Teflon, Teflon, etc. ( are all Teflon's transliteration).

Explanation

PTFE (Teflon) coating is a unique high-performance coatings, combined with heat resistance, chemical inertia and excellent stability and low friction of insulation, paint can not compete with other integrated advantage, it is a flexible application makes it for almost all shapes and sizes of products.

PTFE production methods

PTFE by the polymerization of tetrafluoroethylene by free radical generated. The polymerization industry is stirring in the presence of a large number of water carried out to disperse reaction heat, and easy to control temperature. Polymerization is generally 40 ~ 80 ℃, 3 ~ 26 kgf / cm 2 under pressure, available inorganic persulfate, organic peroxides as initiator, can also be used redox system. Tetrafluoroethylene polymerization per mole exothermic 171.38kJ. Dispersion polymerization to add the type perfluorinated surfactants, such as perfluorooctanoic acid or its salts.

Basic types of Teflon:

* Teflon PTFE:

PTFE (polytetrafluoroethylene) non-stick coating can be used continuously at 260 ℃, the highest temperature 290-300 ℃, low friction coefficient, good wear resistance and excellent chemical stability.

* Teflon FEP:

FEP or F46 (fluorinated ethylene propylene copolymer) nonstick baking melt flow in the formation of non-porous film with excellent chemical stability, excellent non-stick properties, the maximum use temperature of 200 ℃.

* Teflon PFA:

PFA (over fluoroalkyl compounds) paint and FEP as non-stick baking melt flow in the formation of non-porous film. PFA has the advantage of higher continuous use temperature of 260 ℃, more just toughness, particularly suitable for use in high temperature and chemical resistance, anti-sticking field of use.

* Teflon ETFE:

ETFE is a copolymer of ethylene and tetrafluoroethylene, the fluorine resin is the toughest polymers, can form a highly durable coating with excellent chemical resistance, and can work continuously at 150 ℃.

Through the Teflon coating, the following features:

1, not sticky:

Almost all materials are not bonded with Teflon coating. Thin film also showed good adhesion properties are not.

2, heat resistance:

Teflon film with excellent resistance to heat and low temperature tolerance. Short period of time can be high temperature to 300 ℃, generally between 240 ℃ ~ 260 ℃ can be used continuously, with significant thermal stability, it can work in freezing temperatures without embrittlement at high temperature without melting.

3, sliding:

Teflon coating has a lower coefficient of friction. Sliding friction coefficient when the load changed, but the values only between 0.05-0.15.

4, anti-wet:

Teflon coated surface is not cleaning the bathroom and oil production operations are not easy to dip solution, such as a sticky little dirt, simply wipe to clear. Down time, save time and improve the work efficiency.

5, wear resistance:

At high load, have excellent wear resistance. Certain load, wear and do not have the double advantage of adhesion.

6, corrosion resistance:

Teflon is almost free from drugs erosion, can protect the part from being any kind of chemical corrosion.

PTFE is a polymer of tetrafluoroethylene. English abbreviated as PTFE. Trade name "Teflon" (teflon). Known as the "king of plastic." The basic structure of polytetrafluoroethylene. - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 - CF2 -. PTFE is widely used in a variety of needs of anti-acid and organic solvents, it themselves were not toxic, but the raw materials used in the production process of PFOA (PFOA) is considered potentially carcinogenic effects.

Higher molecular weight PTFE, hundreds of thousands of low, high over 10 million above normal for millions of (degree of polymerization of the 104 orders of magnitude, while the polyethylene only 103). General crystallinity of 90 ~ 95%, melting temperature of 327 ~ 342 ℃. CF2 units Teflon molecules arranged by zigzag shape, the radius of the fluorine atoms larger than hydrogen, so adjacent CF2 units can not cross by trans-orientation, but form a spiral twist chain, fluorine atom is almost covered the surface of the polymer chain. This explains the molecular structure of the various properties of PTFE. Temperature is below 19 ℃, the formation of 13 / 6 helix; phase transition at 19 ℃, molecular slightly untied, forming 15 / 7 helix.

It is the temperature at 250 ℃ not melt in the ultra-low temperature of -260 ℃ not brittle. PTFE smooth anomaly, but it is even better than the ice; it is particularly good insulation, a layer of newspaper thick film, is sufficient to withstand the high voltage 1500V.

By the tetrafluoroethylene polymer PTFE is generated by free radical polymerization. The polymerization industry is stirring in the presence of a large number of water carried out to disperse reaction heat, and easy to control temperature. Polymerization is generally 40 ~ 80 ℃, 3 ~ 26 kgf / cm 2 under pressure, available inorganic persulfate, organic peroxides as initiator, can also be used redox system. Tetrafluoroethylene polymerization per mole exothermic 171.38kJ. Dispersion polymerization to add the type perfluorinated surfactants, such as perfluorooctanoic acid or its salts.

Application of PTFE can use compression molding or extrusion processing; also be made of aqueous dispersion for coating, impregnation or into fibers. PTFE in the nuclear, aerospace, electronics, electrical, chemical, machinery, instruments, meters, construction, textile, food industry, widely used as a resistance to high temperature, corrosion resistant material, insulation material, anti-sticking coatings.

Chemical Properties

Insulation:

From the environment and the impact of frequency, volume resistance up to 1018 ohm • cm, dielectric loss, high breakdown voltage.

Resistance to high and low temperature:

Little change on the temperature, a wide range of temperature range, you can use the temperature -190 ~ 260 ℃.

Self-lubricating:

With the smallest coefficient of friction of plastic, is the ideal oil-free lubrication materials.

Surface is not sticky:

Known solid materials can not adhere to the surface, is a minimal surface energy of solid materials.

Resistance to atmospheric aging, irradiation resistance and low permeability: long-term exposure to the atmosphere, surface and performance remained unchanged

Non-flammable:

Limiting oxygen index of 90 less.

Physical properties

PTFE's mechanical properties than soft. Has a very low surface energy.

PTFE (F4, PTFE) with a series of excellent performance: high temperature - long-term use temperature of 200 ~ 260 degrees, low temperature - at -100 degrees is still soft; corrosion resistance - ability aqua regia and all organic solvents; weather-resistant - the best aging life plastics; high lubrication - the smallest has a plastic friction coefficient (0.04); not sticky - the smallest of solid materials with surface tension adhesion without any substance; no poison - with physical inertia; excellent electrical performance, is ideal for C-level insulation. PTFE material, widely used in national defense, atomic energy, oil, radio, electric machinery, chemical industry and other important sectors. Products: PTFE four ethylene rods, tubing, plate, turning sheet. PTFE is a polymer of tetrafluoroethylene. English abbreviated as PTFE. Structural formula. The late 20th century, 30 found that 40 years into industrial production. Nature of the higher molecular weight PTFE, the low hundreds of thousands, up to 10 million or more high, usually several million (degree of polymerization of the 104 orders of magnitude, while the polyethylene only 103). General crystallinity of 90 ~ 95%, melting temperature of 327 ~ 342 ℃. CF2 units Teflon molecules arranged by zigzag shape, as the radius of fluorine atoms larger than hydrogen, so adjacent CF2 units can not cross by trans-orientation, but form a spiral twisted chain, fluorine atom is almost covered the whole surface of the polymer chain. This explains the molecular structure of the various properties of PTFE. Temperature is below 19 ℃, the formation of 13 / 6 helix; phase transition at 19 ℃, molecular slightly untied, forming 15 / 7 helix.

Although perfluorocarbon in the carbon - carbon and carbon - fluorine bond breaking require energy absorption, respectively 346.94 and 484.88kJ/mol, but PTFE depolymerization energy generated only 1mol tetrafluoroethylene 171.38kJ. So when the high temperature pyrolysis, depolymerization of PTFE mainly as tetrafluoroethylene. PTFE at 260,370 and 420 ℃ when the weight loss rate (%) per hour were 1 × 10-4,4 × 10-3 and 9 × 10-2. Can be seen at 260 ℃ Teflon long-term use. As the pyrolysis also yields highly toxic phosgene and by-product fluorine perfluoroisobutylene So, pay special attention to security and to prevent contact with open flame PTFE.

Mechanical properties of its minimal friction coefficient, only polyethylene 1 / 5, which is an important feature of all fluorocarbon surface. Also, because fluoride - very low molecular interaction of carbon chain, it has no adhesive PTFE.

-196 ~ 260 ℃ Teflon in the wider temperature range to maintain good mechanical properties, all the characteristics of fluorocarbon polymer is one not become brittle at low temperatures.

Chemical resistance and weather resistance than molten alkali metals, the PTFE is almost free from any corrosive chemical reagents. For example, in concentrated sulfuric acid, nitric acid, hydrochloric acid, boiling water, even in the king, no change in weight and performance, almost insoluble in all solvents, only slightly soluble in more than 300 ℃ all alkanes (about 0.1g/100g). PTFE does not absorb moisture, combustible, oxygen, ultraviolet radiation are very stable, it has excellent weather resistance.

Electrical properties of PTFE in a wide frequency range of dielectric constant and dielectric loss are low, and breakdown voltage, resistivity, and arc resistance is rather high.

Radiation resistance less radiation resistance of PTFE (104 rad), high-energy radiation caused by the degradation of polymer electrical and mechanical properties decreased significantly.

PTFE (polytetrafluoroethylene) application:

PTFE's unique properties make it in the chemical, petroleum, textile, food, paper, medicine, electronics and machinery industries and marine operations are widely used in the field.

1, polytetrafluoroethylene (PTFE) on the application in the construction

PTFE architectural membrane material, such as TACONIC produced SOLUS products have been widely used in large-scale public facilities: stadium roof system, airport halls, exhibition centers, stations and so on.

 

Light weight
 It weighs only a fraction of traditional building materials
 
High intensity
 Textile fabrics of glass fiber is the highest intensity, which even more than the same diameter of steel wire still strong
 
Flexibility
 Different from most solid building materials, soft Solus products can be stretched into a variety of dynamic arc shape
 
Transmittance
 Uniformity of light transmission through the inner and outer surface to form a soft light scattering
 
Low maintenance
 Used in weaving the period, only a very small amount of cleaning to do. Because the fabric surface is not strong adhesion, is also tense, so rain will wash away the dust
 
Completely inert surface
 Harsh environments, such as fungi, acid rain and other surface work will not weaving
 
Solderability
 Each weaving frame will be welded together into one big roof. Weld strength will be greater than the cloth itself
 
Long period of use
 Period of its use, PTFE coated glass fabric is almost no degradation. Currently, Solus weaving estimated at least 25 years
 
Fire performance
 Solus achieve A-class fire safety assessment of cloth, while it remains a very strong light transmission
 

1, polytetrafluoroethylene (PTFE) in the application of anti-corrosion

As rubber, glass, metal alloys and other materials, defects in the corrosion area, difficult to meet the harsh conditions of temperature, pressure and chemical environment of media co-exist, the resulting loss of a considerable surprise. The PTFE material for its excellent corrosion resistance, has become the petroleum, chemical, textile and other industries the main anti-corrosion material. The specific applications include: corrosive gas pipeline transmission, exhaust pipes, steam pipes, rolling mill high-pressure tubing, aircraft hydraulic system and the cold low pressure system in the high school pipeline, distillation columns, heat exchangers, tank, tower, tank lining, valves and chemical equipment.

Good or bad seals on the machinery and equipment performance efficiency and performance are greatly affected. PTFE material has resistance to corrosion, anti-aging, low friction coefficient and non-sticky, wide temperature range and elastic properties make it very suitable for manufacturing for high corrosion resistance, temperature over 100 ℃ seals. Such as machinery, heat exchangers, pressure vessels, large diameter vessels, valves, pump seals flange trough, glass Fanyingguo, flange, large diameter flange seals, shaft, piston, valve Rod, Worm pumps, rod seals, etc..

2, polytetrafluoroethylene (PTFE), low friction performance in the application of load

As part of some equipment is not appropriate lubrication of friction, such as solvents in the lubricant would be dissolved and the failure of the occasion or the paper, pharmaceutical, food, textile and other industrial products need to avoid oil contamination, so filled PTFE material on the a lubricating machinery and equipment spare parts (direct bearing load) of the best materials. This is because of the friction coefficient is the lowest known solid materials. Specific uses include equipment for chemical industry, papermaking machinery, agricultural machinery bearings, used as piston rings, machine guide, guide ring; in Civil Engineering is widely used as bridges, tunnels, steel roof, large chemical pipelines, storage slot supporting the slider, and as such bridge bearing and bridge swivel.

3, polytetrafluoroethylene (PTFE) in the application of electrical and electronic

PTFE material inherent low loss and dielectric constant so that it can be made small magnet wire for use in micro-motor, thermocouple, control devices; PTFE film is to create capacitor, radio insulation liner, insulated cables, motors and transformers ideal insulating materials, electronic and aerospace industries is also an indispensable material for components; use of fluorine on the oxygen permeability of plastic film, while on the water vapor permeability through the choice of small, can produce oxygen sensor ; use of fluorine plastic at high temperature, high pressure occurs very characteristics of the charge deviation, can produce a microphone, speakers, robot parts, etc.; use of its low refractive index of the properties, manufacture of optical fiber.

4, polytetrafluoroethylene (PTFE) in health care in the medical application

Expanded PTFE material is pure inert, have very strong biological adaptation, will not cause the body's rejection, on the human body has no physiological side effects, can be disinfected by any means, multiple porous structure, which can be used for a variety of recovery solutions , including for soft tissue regeneration and artificial blood vessels and patches for the vascular, cardiac, general surgery and plastic surgery suture.

5, polytetrafluoroethylene (PTFE) of the anti-sticking properties of the application

PTFE material has the smallest solid material surface tension, does not adhere to any material, but also has excellent resistance to high and low temperature characteristics, making it non-stick in the manufacture of anti-sticking, such as the application of very extensive. The anti-sticking technology contains two kinds: the PTFE sheet mounted components or substrate, and the PTFE composite coating or glass cloth with heat shrink the sleeve through the substrate.

With the continuous development of materials, application technology, PTFE material of the three major shortcomings: cold resistance, hard soldering, hard process of melting is gradually being overcome, making it in the optical, electronic, medical, petrochemical, oil seepage, etc. many areas of application prospects even brighter.

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