Briefly about the invention: The Teflon ® coating was accidentally discovered in 1938 by Dr Roy Plunkett, a young chemist at DuPont, who was then conducting experiments with refrigerant gases. This slippery material that doesn’t stick to anything is PTFE (polytetrafluoroethylene), which DuPont later gave the name Teflon ® .
Teflon ® is a registered trademark and may only be used by Chemours.
Dr Roy Plunkett’s note in his notebook
About the invention in detail: Excerpt from the Life and Science supplement
Author: Dr Árpád Máthé
Teflon ® and chance
In April 1938, Dr. Roy Plunkett, a chemist at the American company DuPont, used tetrafluoroethylene (C2F4) as an intermediate to produce a new refrigerant. The 45 kilograms of gas, hot at minus 76 degrees Celsius, was stored in a few dozen small steel bottles. Later, when they opened the shut-off valve, one of the bottles seemed to be empty… No gas came out of the bottle. The valve was removed. It turned out that a white powder from the tetrafluoroethylene gas was deposited on the wall of the bottle. To collect the dust, the bottle was sawn in half. The white powder was found to have the same chemical composition as tetrafluoroethylene gas. Poly(tetrafluoroethylene), in short: PTFE, was formed during storage, regardless of the researchers’ intentions.
Plunkett did not think that tetrafluoroethylene could polymerize during storage, since the polymerization of a similar monomer, vinyl chloride, required a catalyst, a radical initiator. The spontaneous polymerization was also surprising because the researchers were dealing with fluoro-chloro-hydrocarbons (freons) precisely because of their high stability.
Poly(tetrafluoroethylene) was given the name Teflon®. This thermoplastic polymer has a highly crystalline structure. It has the highest chemical resistance of all plastics: it has no solvents. It withstands both cold and heat well: it can be used permanently from minus 269 degrees Celsius to plus 260 degrees Celsius. The least flammable plastic. It meets the strictest food industry and medical requirements, and can even be incorporated into living organisms.
No material sticks to it, even at higher temperatures. That’s why we can bake in Teflon®-coated metal dishes without fat. It cannot be molded using traditional plastic processing methods: its density is higher (2.3 grams/cubic centimeter) than that of bulk plastics, and its price is much higher than theirs.
Thanks to its special application possibilities, more than 50,000 tons of Teflon® are produced worldwide every year.
Teflon ® is a product of radical polymerization of tetrafluoroethylene. It has a high average molecular weight (0.5–1 million), 90 percent crystalline structure and melts at 341 degrees Celsius. It is interesting that the bulked and then cooled polymer melts for the second time already at 327 degrees Celsius. It is stable above this temperature, but the viscosity of the melt is so high (1011 poise at 380 degrees Celsius) that it cannot be processed in the usual way (by extrusion or injection molding). The material consisting of porous particles of different shapes emerging from the suspension polymerization reactors is filtered, dried and ground depending on the needs. A typical PTFE granulate consists of particles with a diameter of 400-800 micrometers. This ground material is pressed into the desired shape at a low temperature, and then the semi-finished product is sintered in an oven (heat-treated at 380 degrees Celsius under pressure for a long time). This is how the particles are assembled into a pore-free, solid material that completely fills the space. This can then be shaped using processes known from the metal industry (drilling, turning, milling, etc.).
Teflon ® is suitable for the production of coatings and fibers in the form of an aqueous dispersion. The raw dispersion is first stabilized with surfactants and then thickened to a dry matter content of 50-60 percent. It is applied to the desired surface in a variety of ways: it is sprayed with propellant gas, it is applied with liquid, the material to be coated is dipped in it or in an electric field, as a result of which the coating is formed.
A Teflon® fiber can also be drawn from an aqueous dispersion. In this case, the dispersion is mixed with a matrix-forming plastic such as viscose. The auxiliary polymer providing the matrix is removed from the fiber bundle by heating, then the fibers are sintered and further stretched.
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Non-stick Very few solid substances will permanently adhere to a TEFLON® finish. Although tacky materials may show some adhesion, almost all substances release easily. |
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Low coefficient of friction The coefficient of friction of TEFLON® is generally in the range of 0.05 to 0.20, depending on the load, sliding speed, and particular TEFLON® coating used. |
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Nonwetting Since surfaces coated with TEFLON® are both oleophobic and hydrophobic, they are not readily wetted. Cleanup is easier and more thorough — in many cases, surfaces are self-cleaning. |
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Heat resistance TEFLON® industrial coatings can operate continuously at temperatures up to 250°C/550°F and can be used for intermittent service on higher temperature with adequate ventilation. (Please contact us!) |
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Unique electrical properties Over a wide range of frequencies, TEFLON® has high dielectric strength, low dissipation factor, and very high surface resistivity. By special techniques, it can even be made electro conductive enough to be used as an anti-static coating. |
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Cryogenic stability Many TEFLON® industrial coatings withstand severe temperature extremes without loss of physical properties. TEFLON® industrial coatings may be used at temperatures as low as -270°C/-454°F. |
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Chemical resistance TEFLON® is normally unaffected by chemical environments. The only chemicals known to affect all TEFLON® industrial coatings are molten alkali metals and highly reactive fluorinating agents. |
| 1. Teflon® PTFE |
| PTFE (polytetrafluoroethylene) non-stick coatings are two-coat (primer/topcoat) systems. These products have the highest operating temperature of any fluoropolymer (250°C), an extremely low coefficient of friction, good abrasion resistance, and good chemical resistance. PTFE is available only in water-based liquid form. |
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| 2. Teflon® FEP |
| FEP (fluorinated ethylene propylene copolymer) non-stick coatings melt and flow during baking to provide nonporous films. These coatings provide excellent chemical resistance. In addition to low friction, FEP coatings have excellent non-stick properties. Maximum use temperature is 205°C. FEP is available in water-based liquid and powder forms. |
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| 3. Teflon® PFA |
| Like FEP, PFA (perfluoroalkoxy) non-stick coatings melt and flow during baking to provide nonporous films. PFA offers the additional benefits of higher continuous use temperature (260°C), film thicknesses up to 1,000 micrometers (40 mils), and greater toughness than PTFE or FEP. This combination of properties makes PFA an excellent choice for a wide variety of uses, especially those involving chemical resistance. PFA is available in both water-based liquid and powder forms. |
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| 4. Teflon® ETFE |
| ETFE is a copolymer of ethylene and tetrafluoroethylene and is also sold under the Tefzel® trademark. Although not fully fluorinated, ETFE has excellent chemical resistance and can operate continuously at 150°C. This resin is the toughest of the fluoropolymers and can be applied at film builds up to 1,000 micrometers (40 mils) to provide a highly durable finish. ETFE is available in powder form. |
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| 5. Teflon-S® one layer coating systems |
| These solvent-based liquid coatings are formulated with special blends of fluoropolymers and other high-performance resins to improve toughness and abrasion resistance. Because the film components stratify during baking, most of the fluoropolymer properties (such as low friction and non-stick character) are retained. The resins provide adhesion and abrasion resistance. These products can sometimes be applied to smooth, clean metal. |
| Technical Properties of TEFLON® |
| MECHANICAL PROPERTIES |
| The values shown in this table represent average experiences from numerous testing sources and are not intended to be specifications. These values will vary depending upon the individual compositions of the primers and topcoats and the systems used. For further information on the properties of these coating systems, and examples of how they have led to the development of new products, increased production rates and resultant cost savings, you should consult DuPont or a Licensed Industrial Applicator. |
| Property | ASTM Standard | Unit | Teflon® PTFE | Teflon® FEP | Teflon® PFA | Teflon® ETFE |
| Specific Gravity | D792 | — | 2,15 | 2,15 | 2,15 | 1,76 |
| Tensile Strength | D1457 D1708 D638 |
MPa | 21-35 | 23 | 25 | 40-47 |
| Elongation | D1457 D1708 D638 |
% | 300-500 | 325 | 300 | 150-300 |
| Flexural Modulus | D790 | MPa (psi) |
500 | 600 | 600 | 1.200 |
| Folding Endurance | D2176 | (MIT) cycles |
>106 | 5-80 x 103 | 10-500 x 103 | 10-27 x 103 |
| Impact Strength | D256 | J/m (ft·lb/in) |
189 | No break | No break | No break |
| Hardness | D2240 | Shore D pencil |
50-65 HB |
56 HB |
60 HB | 72 HB |
| Abrasion Resistance – Bell Abrasion (1) – Sliding Arm (2) – Tabor Abrasion (3) |
— | g/µm mg mg |
85 7,9-9,7 12 |
— 11,1-15,2 14,8 |
— — — |
— 1,.4 — |
| Scratch Resistance scratch master –initial (4) –complete (5) |
— | kg kg |
5,7-7,0 7,3-10,7 |
5,1-11,4 8,5-13,2 |
— — |
— — |
| Coefficient of Friction –static –dynamic |
D1894 | — | 0,12-0,15 0,05-0,10 |
0,12-0,20 0,08-0,3 |
0,2 — |
0,24-0,50 0,3-0,4 |
| Contact Angle (water) | — | degree | 104-111 | 95-105 | 104-111 | 90-100 |
| Notes: 1. Bell Abrasion Tester: grams abrasive/micrometers 2. Sliding Arm Test: 1,000 cycles, 500 gr load, 400 Emery paper, 35.5 sq. cm surface 3. Tabor Abrasion: Cs 17 wheel, 1kg load, 1,000 cycles, weight loss in mg 4. Scratch Master: initial = first sign of substrate 5. Scratch Master: complete = total removal of film |
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| THERMAL PROPERTIES |
Property |
ASTM Standard | Unit | Teflon® PTFE | Teflon® FEP | Teflon® PFA | Teflon® ETFE |
| Melting Point | D3418 | °C | 327 | 260 | 305 | 267 |
| Cure Temperature | — | °C | 380-430 | 360-390 | 380-400 | 300-325 |
| Max. Use Temperature |
— | °C | 270 | 205 | 260 | 150 |
| Intermittent üzemi hőfok |
— | °C | Please contact us! | |||
| Flame Rating** | UL94 | — | VO | VO | VO | VO |
| Limiting Oxygen Index | D2863 | % | >95 | >95 | >95 | 30-36 |
Heat of Combustion |
D240 | MJ/kg (Btu/lb) |
5,1 | 5,1 | 5,3 | 13,7 |
| Thermal Conductivity | — | Btu·in/h·ft2·°F W/m·K |
0,25 | 0,20 | 0,19 | 0,24 |
| ** Statements regarding behavior in a flame situation are not intended to reflect hazards presented by this or any other material when under actual fire conditions. | ||||||
| CHEMICAL PROPERTIES |
| Property | ASTM Standard | Unit | Teflon® PTFE | Teflon® FEP | Teflon® PFA | Teflon® ETFE |
| Chemical/Solvent Resistance | D543 | — | Excellent | Excellent | Excellent | Excellent |
| Water Absorption, 24 h | D570 | % | <0,01 | <0,01 | <0,03 | <0,03 |
| Salt Spray Resistance (1) – on aluminum – on steel |
B-117 | Hours Hours |
744+ 192 |
744+ — |
1000 — |
1000 — |
| Detergent Resistance (2) -on aluminum -on grit-blasted aluminum -on grit-blasted steel |
— | Hours Hours Hours |
264 624 24 |
744 600 480 |
— — — |
— — — |
| Weather Resistance | Florida Exposure | Years Unaffected | 20 | 20 | 10 | 15 |
| Notes: 1. Salt Spray Resistance: 5% NaCl at 35°C/95°C, hours to failure. 2. Detergent Resistance: hours to failure. |
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| ELECTRICAL PROPERTIES |
| Property | ASTM Standard | Unit | Teflon® PTFE | Teflon® FEP | Teflon® PFA | Teflon® ETFE |
| Dielectric Constant | D150 | 1 MHz | 2,1 | 2,1 | 2,1 | 2,6 |
| Dielectic Strength** | D149 | V/µm | 18 | 53 | 80 | 79 |
| Dissipation Factor | D150 | 1 MHz | <0,0001 | 0,0006 | 0,0001 | 0,007 |
| Arc Resistance | D495 | sec | >300 | 300 | >180 | 122 |
| Volume Resistivity | D257 | ohm·cm | >1018 | >1018 | >1018 | >1017 |
| Surface Resistivity | D257 | ohm/sq | >1018 | >1016 | >1017 | >1015 |
| ** Dielectric Strength: 100 micrometers film | ||||||
| Vapor Transmission Rates of TEFLON® FEP Film, 25 µm (1 mil) thickness/per ASTM E-96 (modified) Values measured on thicker specimens and converted to 25 µm (1 mil) |
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Vapor |
Temperature, °C | g/100 sq in. or g/625 sq cm (24 Hours) |
| Acetic Acid | 35° | 0,41 |
| Aceton | 35° | 0,95 |
| Acetophenone | 25° | 0,50 |
| Benzene | 35° | 0,64 |
| Carbon Tetrachloride | 35° | 0,31 |
| Etyl Acetate | 35° | 0,76 |
| Hexane | 35° | 0,56 |
| Hydrochloric Acid, 20% | 25° | <0,01 |
| Piperidine | 25° | 0,04 |
| Red Fuming Nitric Acid | 25° | 7,5-1,4 |
| Sodium Hydroxide, 50% | 25° | <0,01 |
| Sulfuric Acid, 98% | 25° | 0,00001 |
| Water | 39,5° | 0,40 |
All technical advice, application suggestions, recommendations and services are rendered by the seller gratis. They are based on technical data which the Seller believes to be reliable and are intended for use by persons having skill and know-how, at their own discretion and risk. Seller assumes no responsibility for results obtained or damages incurred from their use by Buyer in wholer or in part. Such technical advice, application suggestions, recommendations or services are not to be taken as a license to operate under, or intended to suggest infringement of, any existing patent.
All technical advice, application suggestions, recommendations and services are rendered by the seller gratis. They are based on technical data which the Seller believes to be reliable and are intended for use by persons having skill and know-how, at their own discretion and risk. Seller assumes no responsibility for results obtained or damages incurred from their use by Buyer in wholer or in part. Such technical advice, application suggestions, recommendations or services are not to be taken as a license to operate under, or intended to suggest infringement of, any existing patent.