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Making Teflon Stick​

(This article appeared in Invention & Technology magazine, Summer 2000 www.americanheritage.com and I highly recommend the magazine​

One of the most versatile and familiar products of American chemical engineering, Teflon, was discovered by accident. There are many such tales to be found in the history of industrial chemistry, from vulcanized rubber to saccharin to Post-Its, all of which were stumbled upon by researchers looking for other things. So common, in fact, are unplanned discoveries of this sort that one might expect would-be inventors to simply mix random chemicals all day long until they come up with something valuable. Yet the circumstances behind the Teflon story show how each step along the way drew on the skills and talents of workers who were trained to nurture such discoveries and take them from the laboratory to the market. Teflon was developed at Du Pont, the source of many twentieth-century chemical innovations. It came about as a byproduct of the firm’s involvement with refrigerants. In the early 1930s a pair of General Motors chemists, A. L. Henne and Thomas Midgley, brought samples of two compounds to the Jackson Laboratory at Du Pont’s Chambers Works in Deepwater, New Jersey. The compounds, called Freon 11 and Freon 12, were chlorofluorocarbons (CFCs)—hydrocarbons in which some or all of the hydrogen was replaced with chlorine or fluorine. GM’s research laboratories had developed the family of Freons for its Frigidaire division, which made refrigeration equipment. They were meant to replace existing refrigerants such as ammonia, sulfur dioxide, and propane, which were less efficient than Freons and either too poisonous or too explosive for residential use.
Having made the basic discovery, GM teamed up with Du Pont to take advantage of the latter’s expertise in manufacturing and research and development. The two companies formed a joint venture called Kinetic Chemicals, which by the mid-1930s had isolated and tested a wide range of CFCs and put the most promising ones into mass production. The best seller was refrigerant 114 (later called Freon 114), or retrafluorodichloroethane (CF2ClCF2Cl). Kinetic had agreed to reserve its entire output of Freon 114 for Frigidaire, so in the late 1930s Du Pont was looking for an equally effective refrigerant that it could sell to other manufacturers. One of the chemists assigned to this project was the 27-year-old Roy J. Plunkett, who had been hired in 1936 after completing his doctorate at Ohio State University.
Plunkett was working on a new CFC that he hoped would be a good refrigerant. He synthesized it by reacting tetrafluoroethylene (TFE), a gas at room conditions, with hydrochloric acid. To further this research, Plunkett and his assistant, Jack Rebok, prepared 100 pounds of TFE and stored it in pressure cylinders, to be dispensed as needed. To prevent an explosion or rupture of the cylinder, they kept the canisters in dry ice.
On the morning of April 6, 1938, Rebok connected a canister of TFE to the reaction apparatus he and Plunkett had been using. His standard procedure was to release some TFE into a heated chamber and then spray in hydrochloric acid, but this time, when he opened the valve on the TFE container, nothing came out. A cursory examination did not reveal anything wrong with the valve. Had the gas somehow leaked out? Rebok and Plunkett weighed the cylinder and discovered that most of the gas was still inside. They fiddled with the valve some more, even using a wire to unclog it, but nothing happened.
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Rebok (left) Plunket (right) and another chemist, Bob McHarness, reenact the discovery of Teflon
A frustrated Plunkett removed the valve completely, turned the canister upside down, and shook it. Some flecks of white powder floated out. Plunkett and Rebok sawed open several of the storage canisters and found that their interior walls were lined with a smooth, waxy white coating. In his lab notebook Plunkett wrote, “A white solid material was obtained, which was supposed to be a polymerized product.” This entry shows that he instantly understood what had occurred, even though it was generally believed at the time that a chlorinated or fluorinated ethylene could not be polymerized because previous attempts to do so had failed. Something about the combination of pressure and temperature had forced the TFE molecules to join together in long chains, and the resulting compound turned out to have a most interesting set of properties.
Two days later Plunkett noted some additional characteristics of the intriguing substance: “It is thermoplastic, melts at a temperature approaching red heat, and boils away. It burns without residue; the decompositive products etch glass.” He also observed that it was insoluble in cold and hot water, acetone, Freon 113, ether, petroleum ether, alcohol, pyridine, toluene ethyl acetate, concentrated sulfuric acid, glacial acetic acid, nitrobenzene, isoanyl alcohol, ortho dichlorobenzene, sodium hydroxide, and concentrated nitric acid. Further tests showed that the substance did not char or melt when exposed to a soldering iron or an electric arc. Moisture did not cause it to rot or swell, prolonged exposure to sunlight did not degrade it, and it was impervious to mold and fungus.
Plunkett’s next step was to duplicate the conditions that had produced the first batch of polymerized tetrafluoroethylene (PTFE). After experimentation he succeeded in re-creating what had occurred by chance inside the canisters. On July 1, 1939, he applied for a patent (which he assigned to Kinetic Chemicals) on tetrafluoroethylene polymers. The patent was granted in 1941.
The patent application ended Plunkett’s involvement with his discovery, since at that point the problem shifted from fluorine chemistry, which was his area of expertise, to polymer chemistry and process development. Plunkett was named chemical supervisor of Du Pont’s tetraethyl lead plant and stayed with Du Pont in various positions until his retirement in 1975; he was inducted into the National Inventors Hall of Fame in 1985 and died in 1994.
For about three years Du Pont’s organic chemicals department experimented with ways to produce IFE, also known as TFE monomer, which was the raw material for PTFE. Plunkett and Rebok had produced small batches for laboratory use, but if PTFE was ever going to find a practical use and be produced commercially, the company would have to find a way to turn out TFE monomer in industrial quantities. When the organic group came up with a promising method, Du Pont’s central research and development department began looking into possible polymerization processes.
Spontaneous polymerization of TFE can lead to explosive reactions because heat is released in the process, so it had to be carefully controlled. Experiments by the chemist Robert M. Joyce soon led to a feasible but costly procedure. Meanwhile, Du Pont’s applications group began identifying the properties of PTFE that would be useful in industry, such as its resistance to electric currents and to most chemical reactions. Then came World War II, which gave a large boost to the development of PTFE (and many other technologies).
Scientists working on the Manhattan Project faced the difficult problem of separating the isotope U-235 (which makes up about 0.7 percent of the element uranium in its natural state) from the far more plentiful but inert U-238. The method they settled on was gaseous diffusion, in which a gas is forced through a porous material. Since heavy molecules diffuse more slowly than light ones, multiple repetitions of the diffusion process will yield a gas enriched in the lighter isotopes. Gen. Leslie Groves, director of the Manhattan Project, chose Du Pont to design the separation plant. To make it work, the designers needed equipment that would stand up to the highly corrosive starting material, uranium hexafluoride gas, which destroyed conventional gaskets and seals. PTFE was just what they needed, and Du Pont agreed to reserve its entire output for government use.
For security reasons PTFE was referred to by a code name, K 416, and the small production unit at Arlington, New Jersey, was heavily guarded. Despite the tight security and Du Pont’s efforts to control the polymerization process, the Arlington production unit was wrecked by an explosion one night in 1944. The next morning construction workers stood by while Army and FBI investigators looked for evidence of sabotage. Working with Du Pont chemists, they found that the explosion had been caused by uncontrolled, spontaneous polymerization that was detonated by the exothermic, or heat-releasing, decomposition of TFE to carbon and tetrafluoromethane. When the investigators left, the construction crews took over, working two 12-hour shifts a day. Within two months the unit had been rebuilt with heavy barricades surrounding it.
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How Teflon is made from chloroform and hydrogen fluoride
The Manhattan Project consumed about two-thirds of Arlington’s PTFE output, and the remainder was used for other military applications. It proved to be ideal for the nose cones of proximity bombs because it was both electrically resistive and transparent to radar. It was also used in airplane engines and in explosives manufacturing, where nitric acid would destroy gaskets made of other materials, and as a lining in liquid-fuel tanks, whose cold temperatures could make other linings brittle. When the Army needed tape two-thousandths of an inch thick to wrap copper wires in the radar systems of night bombers, it was painstakingly shaved off a solid block of PTFE at a cost of $100 per pound. The high cost was justified because PTFE did a job nothing else could do.
When peace returned, Du Pont decided to go ahead with commercializing PTFE, since its manifold military uses had shown its great industrial potential. With its unmatched knowledge of polymers, the company was in a good position to take advantage of the postwar manufacturing boom. In 1944 the company had registered the trademark Teflon, probably suggested by the abbreviation TFE. The new substance was an ideal fit for Du Pont’s traditional marketing strategy, which was to shun the manufacture of commodity plastics and specialize in sophisticated materials that could command premium prices. Other materials with some of Teflon’s properties were available, but none were as comprehensively resistant to corrosion, and none of the lubricants or low-friction materials then in use were anywhere near as durable or maintenance-free.





Acid corrodes a rod of ordinary plastic but leaves Teflon unaffected.
The company faced significant obstacles before it could produce large amounts of Teflon uniformly and economically. Company chemists had developed several ways to polymerize TFE, but the properties of the resulting product varied significantly from batch to batch. And nearly every step of the manufacturing process raised problems that no chemical manufacturer had faced before. Equipment had to withstand temperatures and pressures beyond previous limits. Even a minute quantity of oxygen would react with the gases used as raw materials, fouling the process lines and valves.
After the synthesis was completed, fabricating Teflon into useful articles raised another set of difficulties. Its melting point was so high that it could not be molded or extruded by conventional methods. A further problem was caused by the very properties that had made Teflon so valuable to begin with. Chemistry students like to joke about the inventor who isolates a substance that will dissolve anything, then cannot find a container to hold it. With Teflon, Du Pont’s chemists faced the opposite problem: How do you make the greatest nonstick substance ever invented bond to another surface?
Research led to the production of Teflon in three basic forms: granules, a fine powder, and an aqueous dispersion. Borrowing the technique of sintering from powder metallurgy, Teflon was compressed and baked into blocks that could be machined into the required shape. In this process the application of heat did not actually melt the Teflon, but it softened the microscopic granules and made them stick together when pressed. Powder could also be blended with hydrocarbons and cold-compressed to coat wires and make tubing. Aqueous dispersions were used to make enamels that could be sprayed or brushed onto a surface and then baked in place.
Another technique involved etching the surface of a piece of Teflon with specially formulated solvents that extracted some of the fluorine atoms. These solvents left behind a thin, carbon-rich surface layer to which conventional adhesives could bond. Yet another solution was to implant fine particles of silica in the Teflon, creating a rough “sandpaper surface” that would also accept adhesives. This method was not as effective as chemical etching, but it was adequate for some purposes. Du Pont chemists also developed fluorocarbon resins that would stick to both Teflon and metal surfaces. And of course, sheets of Teflon could be attached to other items with screws, bolts, clamps, and other mechanical fasteners.
Machine parts requiring a uniform coating could be immersed in a “fluidized bed”—a layer of Teflon powder that was agitated with a stream of air until it behaved like a liquid. The item to be coated was first heated to 650 degrees Fahrenheit and then dipped in the fluidized bed for a second or two. After the excess powder was blown off, a film of one to two thousandths of an inch was left behind. As with other methods, repeated applications were often required to get a thick enough film. This method was especially useful with irregularly shaped mechanical components, such as valves and rotors, as well as with small items like ball bearings.
By 1948 Du Pont had made enough progress to prepare for full-scale production. Two years later the company’s first commercial Teflon plant, designed to produce a million pounds a year, went on line at the Washington Works, on land once owned by George Washington near Parkersburg, West Virginia. Du Pont stepped up its efforts to market Teflon for industrial applications, promoting the use of tape and sheets for insulation in many kinds of electrical equipment. Teflon was also used for gaskets, packings, valve components, pump components, bearings, sealer plates, and hoppers. To help users understand the polymer’s unusual properties and tricky fabrication requirements, Du Pont sent out a team of scientists to advise customers on integrating Teflon into their production processes. Members of the research, manufacturing, and sales staff met regularly to compare notes.
Within a year Teflon was also being used in commercial food processing. Du Pont saw the potential for expansion in this field but decided to proceed slowly. In bread manufacturing, rollers were coated with Teflon to keep dough from sticking. Teflon-lined bread pans and muffin tins became standard equipment in many bakeries. Teflon coatings also stopped dough from sticking to cookie sheets and reduced the number of damaged cookies that had to be thrown away. In candy factories Teflon coated conveyor belts, hooks for pulling taffy, and the cutting edges of slicing machines. In all these applications, Teflon proved much more effective than the old method of coating the surface with oil or grease.
A 1953 Du Pont television commercial showed a Teflon-coated bread pan and boasted that it had “baked 1,258 loaves of bread and ... never had a drop of grease in it.” The first draft of the script for this ad also predicted that frying pans would be coated with Teflon in the future, but that line was deleted before the commercial was filmed. Du Pont was reluctant to market Teflon-coated cookware for home kitchens because of concerns that misuse might lead to injuries and lawsuits. Until the company could be sure that Teflon was absolutely safe in untrained hands, it preferred to stay with industrial users. Nylon, another Du Pont product, had become a great success in consumer products, but it was not subjected to the extreme conditions that Teflon cookware would encounter.
Du Pont’s tests showed that while Teflon could withstand brief exposure to temperatures as high as 1,000 degrees Fahrenheit, it began to soften at 620 degrees Fahrenheit. This was no problem for baking pans, which are rarely subjected to temperatures above 500 degrees, but it could potentially cause problems with pans used on stovetops. Researchers found that at high temperatures, small quantities of gaseous decomposition products were released. Because some of these gases were toxic and might cause temporary flu-like symptoms, adequate ventilation was required. Although the fumes given off by overheated Teflon pans were less toxic than those given off by heated cooking oil or butter, Du Pont decided to proceed with caution. Even as late as 1960 the company sold less than 10 million pounds of Teflon per year, with receipts of a piddling (by Du Pont standards) $28 million. Expanding consumer uses would be the key to boosting sales, but Du Pont had to convince itself that Teflon was harmless before selling it to the housewives of America.
While Du Pont hesitated, an enterprising French couple took matters into their own hands. Marc Grégoire, an engineer, had heard about Teflon from a colleague who had devised a way to affix a thin layer of it to aluminum for industrial applications. The process involved etching the aluminum with acid to create a microscopically pitted surface, covering the surface with Teflon powder, and heating it to just below its melting point, which caused it to interlock with the aluminum surface.

 

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In France, the birthplace of nonstick cookware an advertisement proclaims: "Tefal never sticks."
Grégoire, an avid fisherman, decided to coat his fishing gear with Teflon to prevent tangles. His wife, Colette, had another idea: Why not coat her cooking pans? Grégoire agreed to try it, and he was successful enough to be granted a patent in 1954.The Grégoires were so happy with the results that they set up a business in their home. Starting around 1955, Marc coated pans in their kitchen and Colette peddled them on the street. French cooks, despite their customary reverence for tradition, snapped them up. Encouraged by this reception, the Grégoires formed the Tefal Corporation in May 1956 and opened a factory.
Soon afterward France’s Conseil Supérieur de l’Hygiene Publique officially cleared Teflon for use on frying pans. The Laboratoire Municipale de Paris and the École Supérieur de Physique et Chimie also declared that Teflon-coated cookware presented no health hazard. In 1958 the French ministry of agriculture approved the use of Teflon in food processing. That same year the Grégoires sold one million items from their factory. Two years later sales approached the three million mark.
Du Pont executives, who were aware of these developments in France, decided to seek the approval of the U.S. Food and Drug Administration (FDA) for wider use of Teflon in cooking and food processing. The company tested frying pans and other cooking surfaces under conditions even more rigorous than those used in France. Du Pont’s researchers concluded that utensils coated with Teflon were “unquestionably safe” for both domestic and commercial cooking. In January 1960 the company gave the FDA four volumes of data, collected over nine years, on the effects of Teflon resins in food handling. Within a few months the FDA decided that the resins did not “present any problems under the Food Additives Amendment.” Despite the favorable FDA decision, Du Pont continued to move slowly, since marketing Teflon-coated cookware was not a high priority. Then one man’s enthusiasm nudged Du Pont into action.









Workers in a Tefal factory
Thomas G. Hardie was an American who admired French culture. After graduating from college, he served in the military, worked for the Marshall Plan in Paris, and became a foreign correspondent for an American newspaper chain. Then he entered his family’s business, Nobelt, a Maryland firm that makes textile machinery. During a business trip to France in 1957 or 1958, Hardie met Marc Grégoire at a party on the Left Bank. The Frenchman enthusiastically told Hardie about his business and the factory he was building in a Paris suburb. Hardie was intrigued by Grégoire’s tale of the fast-selling cookware.
After Hardie went home to Maryland, he decided that the popular French pans would sell in the United States too. He went back to Paris to meet with Grégoire, who was reluctant to do business with an American because he didn’t trust Yankees. But Hardie was very persuasive and eventually won Grégoire’s confidence. With visions of quick success, he returned to the States with the rights to manufacture nonstick cookware using Tefal’s process.
During the next two years Hardie called on many American cookware manufacturers, trying to persuade them to make Teflon-coated pans. He had no success because the idea of nonstick pans was simply too new. All these rejections turned Hardie’s business venture into a personal crusade. Although he had no experience in the import business, he cabled the French factory to ship him 3,000 Tefal pans, which he warehoused in a barn on his sheep farm in Maryland. He sent free sample pans, along with promotional literature, to housewares buyers at 200 department stores. Not one of them placed an order.











Half-inch Teflon tubing being extruded, 1955.
Next Hardie met with an executive at Du Pont in Wilmington, Delaware. By describing the success of nonstick pans in France, he was able to convince the executive that cookware could be a valuable new market. When the executive objected that the name Tefal was too close to Teflon, Hardie agreed to market his imported French pans under the name T-fal. Later a Du Pont salesman was assigned to accompany Hardie on a visit to Macy’s in New York City. There, in a tiny basement office, a buyer named George Edelstein placed a small order. Hardie was so excited that he sent a victory cable to the French factory. On December 15, 1960, during a severe snowstorm, the T-fal “Satisfry” skillets went on sale for $6.94 at Macy’s Herald Square store. To almost everyone’s amazement, the pans quickly sold out.
Shortly afterward Hardie made his second sale when he telephoned Roger Horchow, a buyer for the Dallas department store Neiman Marcus. Horchow agreed to test a sample skillet even though his store didn’t have a housewares department. He gave the skillet to Helen Corbitt, a cookbook editor who ran a popular cooking school in Dallas. Corbitt loved it, prompting Neiman Marcus to place a large order and run a half-page newspaper advertisement. The store sold 2,000 skillets in a week. Hot-chow later recalled, “Skillets were piled up, still in the shipping crates, as in a discount house, with the salesladies handing them out to customers like hotcakes at an Army breakfast.” The news spread to other department stores. Buyers jumped on the nonstick bandwagon, and Hardie was swamped with orders.
The inventory in Hardie’s barn was quickly exhausted. He phoned France daily to ask for more pans, but the French plant couldn’t work fast enough to supply both sides of the Atlantic. Hardie flew to France to press his case with Grégoire. He even lent Tefal $50,000 to expand its facilities, but it still could not meet the American demand. To cope with the avalanche of orders, which reached a million pans per month in mid-1961, Hardie built his own factory in Timonium, Maryland.
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Starting with Apollo, NASA used Teflon cloth and Teflon-coated fibers in its space suits.
Unfortunately for him, around the same time, several major American cookware companies decided that the time was right to start making Teflon pans. Suddenly the market was saturated with nonstick cookware. Because the American companies had no experience with Teflon coatings, much of it was inferior to the French product, and nonstick pans soon acquired a bad name. Just as quickly as the U.S. demand for nonstick pans had soared, it plummeted, and warehouses were filled with unsold stock. Hardie sold his factory and focused on his family’s business. (T-fal cookware, the standard of quality in the, early 1960s, is still being manufactured and is sold in stores in the United States and abroad.)
Despite the problems with early Teflon cookware, Du Pont’s managers still believed that it had enormous potential. So the company commissioned some research. Six thousand consumers, along with a sampling of professionals in the cookware business, were asked what was wrong with Teflon products. The respondents overwhelmingly liked the idea of Teflon cookware; the problem lay with faulty production methods that turned out shoddy pans whose coatings scraped off much too easily.
Du Pont knew that cookware could be more than just a way to sell lots of Teflon. It could also be an invaluable marketing tool, a vehicle to familiarize vast numbers of consumers with Teflon and its properties. Conversely, low-quality merchandise could only harm the product’s reputation. As a result the company established coating standards for manufacturers and initiated a certification program, complete with an official seal of approval for Teflon kitchenware. To verify compliance with its standards, Du Pont performed more than 500 tests per month on cookware at its Marshall Laboratories in Philadelphia.
The Du Pont certification program was so successful that a marketing survey in the mid-1960s found that 81 percent of homemakers who had purchased nonstick pans were pleased with them. By 1968 Du Pont had developed Teflon II, which not only prevented food from sticking to the pans but was also (supposedly) scratch-resistant. Later generations of Teflon cookware, with thicker coatings and improved bonding, would be introduced under the trade names Silverstone in 1976 and Silverstone Supra in 1986.
As Teflon became better known to consumers, rumors began to circulate that it was unsafe. Tales sprang up about how Teflon had caused the mysterious deaths of unidentified workers. In other versions users of nonstick cookware had suffered the flu or seizures after breathing Teflon fumes. Industrial safety bulletins and at least one medical journal warned readers of Teflon’s supposed dangers.






An assortment of industrial parts made from granular PTFE shows the material's versatility and the wide range of applications in which it can be used.
Whenever one of these false reports came to Du Pont’s attention, the company demanded a published retraction. It also published a booklet called The Anatomy of a Rumor that summarized the results of research carried out at Du Pont and elsewhere. In addition, Du Pont tried to set the record straight by acknowledging whatever minor problems could be documented. The company admitted that there had been isolated incidents of “polymer fume fever,” which produced symptoms similar to those of influenza for a brief period but had no lasting effects. It also acknowledged at least one case of a worker suffering “the shakes” after smoking cigarettes that might have been contaminated with Teflon dust. In fact, as early as 1954 Du Pont had instructed its employees not to smoke or carry cigarettes with them while working with Teflon. However, no serious illnesses or injuries had ever been linked to Teflon.
When Teflon cookware was introduced, many national magazines printed articles about the new products. Most discussed the safety issue, and several mentioned the rumors, but none gave any credence to the gossip. Nevertheless, Consumer Reports got so much mail about the rumors after a 1961 article that the editors had to print a second article refuting them again. As late as 1973 Consumer Reports was still receiving mail on the “old bugaboo about nonsticks,” prompting the editors to publish yet another article emphasizing that they knew of “no consumer illnesses resulting from... nonstick cookware in ordinary home use.”
As nonstick cookware became accepted, Teflon made the transition from a low-volume specialty material used chiefly in industry to a mass-market consumer item. Today Teflon is used to insulate fabrics in tablecloths and carpets and to coat the surfaces of steam irons. Teflon plumbing pipes and valves can be found in many new homes; Teflon flakes add toughness to nail polish. In fiber form, as part of the fabric known as Gore-Tex, it is beloved by campers and skiers for its ability to insulate while wicking moisture from the skin. It can also be found in pacemakers, dentures, medical sutures, artificial body parts, printed circuits, cables, space suits, and thousands of other manufactured products. The surest sign of the slippery material’s success is its adoption as a slang term in political discourse, where Teflon is used to describe an officeholder who unaccountably remains popular despite having opinions with which one disagrees.
While the discovery of Teflon was unplanned, the rest of its story is anything but accidental. Plunkett’s training in fluorine chemistry allowed him to recognize what he had found and to analyze its properties, a byway he might not have been able to explore in a smaller firm. When the project grew beyond laboratory scale, he knew he could hand it off to other departments with confidence. Du Pont had the knowledge base to find ways of producing the monomer cheaply enough, controlling the polymerization, applying the useful but hard-to-handle polymer to industrial use, and making sure that consumer products were durable, safe, and reliable. Large research groups can have their disadvantages, but in the case of Teflon, Du Pont’s size was a critical ingredient in its success.
Anne Cooper Funderburg is a freelance writer in Mandeyule, Louisiana, who writes about all facets of American history.
visits since October 26, 2000

 

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Teflon is the registered trade name of the highly useful plastic material polytetrafluoroethylene (PTFE). PTFE is one of a class of plastics known as fluoropolymers. A polymer is a compound formed by a chemical reaction which combines particles into groups of repeating large molecules. Many common synthetic fibers are polymers, such as polyester and nylon. PTFE is the polymerized form of tetrafluoroethylene. PTFE has many unique properties, which make it valuable in scores of applications. It has a very high melting point, and is also stable at very low temperatures. It can be dissolved by nothing but hot fluorine gas or certain molten metals, so it is extremely resistant to corrosion. It is also very slick and slippery. This makes it an excellent material for coating machine parts which are subjected to heat, wear, and friction, for laboratory equipment which must resist corrosive chemicals, and as a coating for cookware and utensils. PTFE is used to impart stain-resistance to fabrics, carpets, and wall coverings, and as weatherproofing on outdoor signs. PTIZE has low electrical conductivity, so it makes a good electrical insulator. It is used to insulate much data communication cable, and it is essential to the manufacture of semi-conductors. PTFE is also found in a variety of medical applications, such as in vascular grafts. A fiberglass fabric with PTFE coating serves to protect the roofs of airports and stadiums. PTFE can even be incorporated into fiber for weaving socks. The low friction of the PTFE makes the socks exceptionally smooth, protecting feet from blisters.
History

PTFE was discovered accidentally in 1938 by a young scientist looking for something else. Roy Plunkett was a chemist for E.I. du Pont de Nemours and Company (Du Pont). He had earned a PhD from Ohio State University in 1936, and in 1938 when he stumbled upon Teflon, he was still only 27 years old. Plunkett's area was refrigerants. Many chemicals that were used as refrigerants before the 1930s were dangerously explosive. Du Pont and General Motors had developed a new type of non-flammable refrigerant, a form of Freon called refrigerant 114. Refrigerant 114 was tied up in an exclusive arrangement with General Motor's Frigidaire division, and at the time could not be marketed to other manufacturers. Plunkett endeavored to come up with a different form of refrigerant 114 that would get around Frigidaire's patent control. The technical name for refrigerant 114 was tetrafluorodichloroethane. Plunkett hoped to make a similar refrigerant by reacting hydrochloric acid with a compound called tetrafluoroethylene, or TFE. TFE itself was a little known substance, and Plunkett decided his first task was to make a large amount of this gas. The chemist thought he might as well make a hundred pounds of the gas, to be sure to have enough for all his chemical tests, and for toxicological tests as well. He stored the gas in metal cans with a valve release, much like the cans used commercially today for pressurized sprays like hair spray. Plunkett kept the cans on dry ice, to cool and liquefy the TFE gas. His refrigerant experiment required Plunkett and his assistant to release the TFE gas from the cans into a heated chamber. On the morning of April 6, 1938, Plunkett found he could not get the gas out of the can. To Plunkett and his assistant's mystification, the gas had transformed overnight into a white, flaky powder. The TFE had polymerized.
Polymerization is a chemical process in which molecules combine into long strings. One of the best known polymers is nylon, which was also discovered by researchers at Du Pont. Polymer science was still in its infancy in the 1930s. Plunkett believed that TFE could not polymerize, and yet it had somehow done so. He sent the strange white flakes to Du Pont's Central Research Department, where teams of chemists analyzed the stuff. The polymerized TFE was curiously inert. It did not react with any other chemicals, it resisted electric currents, and it was extremely smooth and slick. Plunkett was able to figure out how the TFE gas had accidentally polymerized, and he took out a patent for the polymerized substance, polytetrafluoroethylene, or PTFE.
PTFE was initially expensive to produce, and its value was not clear to Plunkett or the other scientists at Du Pont. But it came into use in World War II, during the development of the atomic bomb. Making the bomb required scientists to handle large amounts of the caustic and toxic substance uranium hexafluoride. Du Pont provided PTFE-coated gaskets and liners that resisted the extreme corrosive action of uranium hexafluoride. Du Pont also used PTFE during the war for making nose cones of certain other bombs. Du Pont registered the trademark name Teflon for its patented substance in 1944, and continued to work after the war on cheaper and more effective manufacturing techniques. Du Pont built its first plant for the production of Teflon in Parkersburg, West Virginia in 1950. The company marketed Teflon after the war's end as a coating for machined metal parts. In the 1960s, Du Pont began marketing cookware coated with Teflon. The slick Teflon coating resisted the stickiness of even scorched food, so cleaning the pans was easy. The company marketed Teflon for a variety of other uses as well. Other related fluoropolymers were developed and marketed in ensuing decades, some of which were easier to process than PTFE. Du Pont registered another variant of Teflon in 1985, Teflon AF, which is soluble in special solvents.
Raw Materials

PTFE is polymerized from the chemical compound tetrafluoroethylene, or TFE. TFE is synthesized from fluorspar, hydrofluoric acid, and chloroform. These ingredients are combined under high heat, an action known as pyrolosis. TFE is a colorless, odorless, nontoxic gas which is, however, extremely flammable. It is stored as a liquid, at low temperature and pressure. Because of the difficulty of transporting the flammable TFE, PTFE manufacturers also manufacture their own TFE on site. The polymerization process uses a very small amount of other chemicals as initiators. Various initiators can be used, including ammonium persulfate or disuccinic acid peroxide. The other essential ingredient of the polymerization process is water. The Manufacturing Process

PTFE can be produced in a number of ways, depending on the particular traits desired for the end product. Many specifics of the process are proprietary secrets of the manufacturers. There are two main methods of producing PTFE. One is suspension polymerization. In this method, the TFE is polymerized in water, resulting in grains of PTFE. The grains can be further processed into pellets which can be molded. In the dispersion method, the resulting PTFE is a milky paste which can be processed into a fine powder. Both the paste and powder are used in coating applications.
Making the TFE

• 1 Manufacturers of PTFE begin by synthesizing TFE. The three ingredients of TFE, fluorspar, hydrofluoric acid, and chloroform are combined in a chemical reaction chamber heated to between 1094-1652°F (590-900°C). The resultant gas is then cooled, and distilled to remove any impurities.

Suspension Polymerization

• 2 The reaction chamber is filled with purified water and a reaction agent or initiator, a chemical that will set off the formation of the polymer. The liquid TFE is piped into the reaction chamber. As the TFE meets the initiator, it begins to polymerize. The resulting PTFE forms solid grains that float to the surface of the water. As this is happening, the reaction chamber is mechanically shaken. The chemical reaction inside the chamber gives off heat, so the chamber is cooled by the circulation of cold water or another coolant in a jacket around its outsides. Controls automatically shut off the supply of TFE after a certain weight inside the chamber is reached. The water is drained out of the chamber, leaving a mess of stringy PTFE which looks somewhat like grated coconut.
• 3 Next, the PTFE is dried and fed into a mill. The mill pulverizes the PTFE with rotating blades, producing a material with the consistency of wheat flour. This fine powder is difficult to mold. It has "poor flow," meaning it cannot be processed easily in automatic equipment. Like unsifted wheat flour, it might have both lumps and air pockets. So manufacturers convert this fine powder into larger granules by a process called agglomeration. This can be done in several ways. One method is to mix the PTFE powder with a solvent such as acetone and tumble it in a rotating drum. The PTFE grains stick together, forming small pellets. The pellets are then dried in an oven.
• 4 The PTFE pellets can be molded into parts using a variety of techniques. However, PTFE may be sold in bulk already pre-molded into so-called billets, which are solid cylinders of PTFE. The billets may be 5 ft (1.5 m) tall. These can be cut into sheets or smaller blocks, for further molding. To form the billet, PTFE pellets are poured into a cylindrical stainless steel mold. The mold is loaded onto a hydraulic press, which is something like a large cabinet equipped with weighted ram. The ram drops down into the mold and exerts force on the PTFE. After a certain time period, the mold is removed from the press and the PTFE is unmolded. It is allowed to rest, then placed in an oven for a final step called sintering.
• 5 The molded PTFE is heated in the sintering oven for several hours, until it gradually reaches a temperature of around 680°F (360°C). This is above the melting point of PTFE. The PTFE particles coalesce and the material becomes gel-like. Then the PTFE is gradually cooled. The finished billet can be shipped to customers, who will slice or shave it into smaller pieces, for further processing.

Dispersion polymerization

• 6 Polymerization of PTFE by the dispersion method leads to either fine powder or a paste-like substance, which is more useful for coatings and finishes. TFE is introduced into a water-filled reactor along with the initiating chemical. Instead of being vigorously shaken, as in the suspension process, the reaction chamber is only agitated gently. The PTFE forms into tiny beads. Some of the water is removed, by filtering or by adding chemicals which cause the PTFE beads to settle. The result is a milky substance called PTFE dispersion. It can be used as a liquid, especially in applications like fabric finishes. Or it may be dried into a fine powder used to coat metal.

Nonstick cookware

• 7 One of the most common and visible uses of PTFE is coating for nonstick pots and pans. The pan must be made of aluminum or an aluminum alloy. The pan surface has to be specially prepared to receive the PTFE. First, the pan is washed with detergent and rinsed with water, to remove all grease. Then the pan is dipped in a warm bath of hydrochloric acid in a process called etching. Etching roughens the surface of the metal. Then the pan is rinsed with water and dipped again in nitric acid. Finally it is washed again with deionized water and thoroughly dried.
• 8 Now the pan is ready for coating with PTFE dispersion. The liquid coating may be sprayed or rolled on. The coating is usually applied in several layers, and may begin with a primer. The exact makeup of the primer is a proprietary secret held by the manufacturers. After the primer is applied, the pan is dried for a few minutes, usually in a convection oven. Then the next two layers are applied, without a drying period in between. After all the coating is applied, the pan is dried in an oven and then sintered. Sintering is the slow heating that is also used to finish the billet. So typically, the oven has two zones. In the first zone, the pan is heated slowly to a temperature that will evaporate the water in the coating. After the water has evaporated, the pan moves into a hotter zone, which sinters the pan at around 800°F (425°C) for about five minutes. This gels the PTFE. Then the pan is allowed to cool. After cooling, it is ready for any final assembly steps, and packaging and shipping.

 

[asus450000]

Quality Control

Quality control measures take place both at the primary PTFE manufacturing facility and at plants where further processing steps, such as coatings, are done. In the primary manufacturing facility, standard industrial procedures are followed to determine purity of ingredients, accuracy of temperatures, etc. End products are tested for conformance to standards. For dispersion PTFE, this means the viscosity and specific gravity of the dispersion is tested. Other tests may be performed as well. Because Teflon is a trademarked product, manufacturers who wish to use the brand name for parts or products made with Teflon PTFE must follow quality control guidelines laid down by Du Pont. In the case of nonstick cookware manufacturers, for example, the cookware makers adhere to Du Pont's Quality Certification Program, which requires that they monitor the thickness of the PTFE coating and the baking temperature, and carry out adhesion tests several times during each shift.
Byproducts/Waste

Though PTFE itself is non-toxic, its manufacture produces toxic byproducts. These include hydrofluoric acid and carbon dioxide. Work areas must be adequately ventilated to prevent exposure to gases while PTFE is being heated, or when it cools after sintering. Doctors have documented a particular illness called polymer fume fever suffered by workers who have inhaled the gaseous byproducts of PTFE manufacturing. Workers must also be protected from breathing in PTFE dust when PTFE parts are tooled.
Some waste created during the manufacturing process can be reused. Because PTFE was at first very expensive to produce, manufacturers had high incentive to find ways to use scrap material. Waste or debris generated in the manufacturing process can be cleaned and made into fine powder. This powder can be used for molding, or as an additive to certain lubricants, oils, and inks.
Used PTFE parts should be buried in landfills, not incinerated, because burning at high temperatures will release hydrogen chloride and other toxic substances. One study released in 2001 claimed that PTFE also degrades in the environment into one substance that is toxic to plants. This is trifluoroacetate, or TFA. While current levels of TFA in the environment are low, the substance persists for a long time. So TFA pollution is possibly a concern for the future.


حاجی فقط اگه بتونی هر چه سیع تر اگه ممکنه ترجمرو برسونی خیلی ممنونت می شم انشاالله خدا وند نگه دار خودت و عزیزات باشه و هر چی از قادر متعال می خایی دعا می کنم بهت بده

مهندس میدونم از یک صفحه اینا بیشترن ولی منتظر ترجمه دون به دونش هستم

یاعلی و همینا که از من تایپ شده منظورم قبلیاشه بیزحمت
علی یار و یاورت

 

[مجتبی ورشاوی2]

[FONT=&quot]part-1
Making Teflon Stick[/FONT][FONT=&quot][/FONT]
​

[FONT=&quot]ساخت چسب تفلون [/FONT]​

[FONT=&quot](This article appeared in [/FONT][FONT=&quot]Invention & Technology magazine, Summer 2000 [/FONT]​

[FONT=&quot]این نوشته توسط مجله تکنولوژی واختراعات درتابستان2000فراهم گردیده است [/FONT]​

[FONT=&quot]www.americanheritage.com[/FONT][FONT=&quot] and I highly recommend the magazine[/FONT]​

[FONT=&quot]سایت امریکن هریتیج و بنده بسیار به این مجله توصیه می نماییم . [/FONT][FONT=&quot][/FONT]​

[FONT=&quot]
one of the most versatile and familiar products of American chemical engineering, Teflon, was discovered by accident.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]تفلون؛ یکی از پرکاربرد ترین وهمه فن حریف ترین خانواده ها در مهندسی شیمی آمریکا فقط با یک تصادف خلق شد . [/FONT]​

​

[FONT=&quot] There are many such tales to be found in the history of industrial chemistry, from vulcanized rubber to saccharin to Post-Its, all of which were stumbled upon by researchers looking for other things.[/FONT]​

​

[FONT=&quot]خیلی دیگر از این قبیل یافته ها درتاریخ صنایع شیمی وجود دارد- از ولکانیزه کردن رزین تا ساخارین –همه به خطا از کنار تحقیقات برای چیزهای دیگر تولید شده اند .[/FONT]​

​

[FONT=&quot] So common, in fact, are unplanned discoveries of this sort that one might expect would-be inventors to simply mix random chemicals all day long until they come up with something valuable. [/FONT]​

​

[FONT=&quot]عموما درحقیقت ما اینچنین فکر میکنیم که درتحقیقات بدون برنامه ریزی از این دست ,محقق همه روزه به ترکیب کردن رندوم مواد شیمیایی می پردازد تا چیز بدرد بخوری بدست بیاورد. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]Yet the circumstances behind the Teflon story show how each step along the way drew on the skills and talents of workers who were trained to nurture such discoveries and take them from the laboratory to the market. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]اما واقعه ای که درپشت داستان تفلون بود نشان داد که چگونه هر مرحله در راه به تدریج مهارت ها را شکل میدهد واستعداد کارکنانی که بصورت عادی مانند یک کاشف تربیت می شوند چگونه آنها را از آزمایشگاه به بازار رهنمون می گردد . [/FONT]​

​

[FONT=&quot]Teflon was developed at Du Pont, the source of many twentieth-century chemical innovations. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]تفلون در دویه پوت توسعه داده شد –یکی ازمصادر اصلی نو آوری های قرن بیستم در شیمی. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]It came about as a by product of the firm’s involvement with refrigerants. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]تفلون از مسیر گرفتاری های کارخانه ها باسردکننده ها پدید آمد .[/FONT]​

​

[FONT=&quot]In the early 1930s a pair of General Motors chemists, A. L. Henne and Thomas Midgley,[/FONT]​

​

[FONT=&quot]در1930دوتن ازشیمیست های جنرال موتورز شیمی یعنی ای ال هینی وتوماس میدگلی [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] brought samples of two compounds to the Jackson Laboratory at Du Pont’s Chambers Works in Deepwater, New Jersey.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]نمونه ای از دوترکیب رااز لابراتوار اتاق کارجکسون در دوی پونت واقع در دیپ واتر نیوجرسی را دریافت کردند. [/FONT]​

​

[FONT=&quot] The compounds, called Freon 11 and Freon 12, were chlorofluorocarbons (CFCs)—hydrocarbons in which some or all of the hydrogen was replaced with chlorine or fluorine. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]ترکیب فرئون 11 و12 نامیده می شد-همان کلرو فلورو کربن" سی اف سی" [/FONT]​

​

[FONT=&quot]دراین ترکیب همه هیدروژن ها با کلرین یا فلورین جایگزین شده اند.[/FONT]​

​

[FONT=&quot]GM’s research laboratories had developed the family of Freons for its Frigidaire division, which made refrigeration equipment.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]لابراتوار جی ام در حال توسعه خانواده ای از فرئون ها برای بخش یخچالهای خود بود که تجهیزات یخچال راتولید می کرد.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] They were meant to replace existing refrigerants such as ammonia, sulfur dioxide, and propane, which were less efficient than Freons and either too poisonous or too explosive for residential use.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] آنها به دنبال آن بودند که برای جایگزینی موادی مانند آمونیاک ، دی اکسید گوگرد ، و پروپان ، که کمتر مانند فرئون موثر بودند و یا بیش از حد سمی و یا بیش از حد قابل انفجار در استفاده مسکونی راهی بیابند .[/FONT][FONT=&quot]
Having made the basic discovery, GM teamed up with Du Pont to take advantage of the latter’s expertise in manufacturing and research and development. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]این یک اساس برای تحقیقات بیشتر راپدید آورد- کمپانی های جی ام و دوی پوت تحقیقات وتوسعه در ساخت این مطلوب را پی گرفتند.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]The two companies formed a joint venture called Kinetic Chemicals, which by the mid-1930s had isolated and tested a wide range of CFCs and put the most promising ones into mass production[/FONT][FONT=&quot].[/FONT]​

​

[FONT=&quot]دو کمپانی یک همکاری را شکل دادند که کینتیک شمیکال نامیده می شدکه از 1930 تست محدوده وسیعی از سی اف سی ها را پی گرفت ویکی از بهترین ها را در یک تولید واحد قرار داد.[/FONT]​

​

[FONT=&quot]. The best seller was refrigerant 114 (later called Freon 114), or retrafluorodichloroethane (CF2ClCF2Cl).[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]بهترین ترکیب تجاری سی اف سی 114 بود.[/FONT]​

​

[FONT=&quot] Kinetic had agreed to reserve its entire output of Freon 114 for Frigidaire, so in the late 1930s Du Pont was looking for an equally effective refrigerant that it could sell to other manufacturers.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]کینتیک با فرئون 114 برای یخچال ها موافقت کرد بنابراین در اواخر 1930دوی پونت نیز به دنبال سرد کننده ای گشت که بتواندآن را به دیگر تولید کنندگان بفروشد .[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] One of the chemists assigned to this project was the 27-year-old Roy J. Plunkett, who had been hired in 1936 after completing his doctorate at Ohio State University.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]یکی از شیمیدان هایی که برای این پروژه انتخاب شده بود فقط 27 سال سن داشت و روی جی پلانکت نام داشت .[/FONT]​

​

[FONT=&quot]و پس از کسب دکترا از دانشگاه اوهایو درسال 1936 استخدام شده بود [/FONT]​

​

[FONT=&quot]
Plunkett was working on a new CFC that he hoped would be a good refrigerant. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]پلانکت برروی یک سی اف سی جدید کار میکرد که اوامیدواربود یک سرد کننده خوب باشد .[/FONT]​

​

[FONT=&quot]He synthesized it by reacting tetrafluoroethylene (TFE), a gas at room conditions, with hydrochloric acid. To further this research, Plunkett and his assistant, Jack Rebok, prepared 100 pounds of TFE and stored it in pressure cylinders, to be dispensed as needed. To prevent an explosion or rupture of the cylinder, they kept the canisters in dry ice.[/FONT]​

​

[FONT=&quot]او به سنتز آن با تترا فلورو اتیلن که دردمای اتاق بصورت گاز است با هیدروکلریک اسید پرداخت برای این تحقیقات پلانکت ودستیارش جک ربوک برای زمان نیاز 100پاند از تی اف ای را آماده کردند ودر یک سیلندر تحت فشار ذخیره نمودند . [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]برای جلوگیری از هر انفجار ویا از هم گسیختگی سیلندر آنها آن را درقوطی یخ خشک قرار دادند. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]
On the morning of April 6, 1938, Rebok connected a canister of TFE to the reaction apparatus he and Plunkett had been using.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]دربعدازظهر ششم آوریل 1938 ربوک یکی از قوطی ها را " قوطی حامل تی اف تی را "به دستگاهی که پلانکت با آن آزمایش می کرد متصل نمود .[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] His standard procedure was to release some TFE into a heated chamber and then spray in hydrochloric acid, but this time, when he opened the valve on the TFE container, nothing came out.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]روش استاندارد او به این صورت بود که مقداری تی اف تی را به یک محفظه گرم منتقل می نمود وسپس آن را به محیط هیدروکلریک اسید اسپری می کرد .[/FONT]​

​

[FONT=&quot]اما این بار وقتی او شیر را گشود هیچ چیزی بیرون نیامد. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] A cursory examination did not reveal anything wrong with the valve.[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]بررسی سریع مشکلی در شیر را نشان نمی داد .[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot] Had the gas somehow leaked out? Rebok and Plunkett weighed the cylinder and discovered that most of the gas was still inside. [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]شاید گاز به بیرون نشت نموده بود؟ ربوک وپلانکت سیلندر را وزن کردند ودریافتند که از زمانی که گاز داخل آن بوده سنگین تر شده است . [/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]They fiddled with the valve some more, even using a wire to unclog it, but nothing happened[/FONT][FONT=&quot][/FONT]​

​

[FONT=&quot]
آنها کمی شیر را دستکاری کردند وحتی سیمی را برای باز کردن آن داخل کردند اما هیچ چیز اتفاق نیفتاد.







[/FONT]
[FONT=&quot]




[/FONT][FONT=&quot][/FONT]

[FONT=&quot] [/FONT]​

​

 

[مجتبی ورشاوی2]

Part2​

​

Rebok (left) Plunket (right) and another chemist, Bob McHarness, reenact the discovery of Teflon
A frustrated Plunkett removed the valve completely, turned the canister upside down, and shook it.[FONT=&quot][/FONT]​

​

[FONT=&quot]ربوک وپلانکت ویک شیمیدان دیگر باب مک هارنس نمایش کشف تفلون را اجرا کردند [/FONT]​

​

[FONT=&quot]پلانکت درمانده شیر را به کلی باز کرد ومحفظه را چرخاند وآن را تکان داد [/FONT]​

​

Some flecks of white powder floated out.[FONT=&quot][/FONT]​

​

[FONT=&quot]کمی ذرات پودری بیرون ریخت .[/FONT]​

​

Plunkett and Rebok sawed open several of the storage canisters and found that their interior walls were lined with a smooth, waxy white coating.[FONT=&quot][/FONT]​

​

[FONT=&quot]پلانکت وربوک محفظه ها را گشودند ودیدند که دیواره های داخلی آنها با یک لایه یک دست سفید واکس مانند پوشیده شده است [/FONT]​

​

In his lab notebook Plunkett wrote, “A white solid material was obtained, which was supposed to be a polymerized product.[FONT=&quot][/FONT]​

​

[FONT=&quot]پلانکت در دفتر یادداشت آزمایشگاه نوشت " یک جامد سفید رنگ بدست آمده است, به نظر می رسد یک پلی مر تولید شده است. [/FONT]​

​

” This entry shows that he instantly understood what had occurred, even though it was generally believed at the time that a chlorinated or fluorinated ethylene could not be polymerized because previous attempts to do so had failed.[FONT=&quot][/FONT]​

​

[FONT=&quot]این نشان می دهد که او بی درنگ پی به واقعیت ماجرا برده بوده است ,حتی فکر کرده بوده که کلرین فلورین تولید نشده است چون آنچه انجام داده بود ناموفق عمل کرده است. [/FONT]​

​

Something about the combination of pressure and temperature had forced the TFE molecules to join together in long chains, and the resulting compound turned out to have a most interesting set of properties.[FONT=&quot][/FONT]​

​

[FONT=&quot]چیزی در میان فشار و درجه دما باعث شده بود تا ملکول های تی اف ای با هم پیوند طولانی برقرار کنند و خروجی آن ماده ای باویژگی های جالب باشد. [/FONT]​

​

Two days later Plunkett noted some additional characteristics of the intriguing substance:[FONT=&quot][/FONT]​

​

[FONT=&quot]چند روز بعد پلانکت چیز جدیدی در مورد ماده جدید یادداشت کرد .[/FONT]​

​

“It is thermoplastic, melts at a temperature approaching red heat, and boils away. It burns without residue; the decompositive products etch glass.[FONT=&quot][/FONT]​

​

[FONT=&quot]این یک ترموپلاستیک است ,زیرا در شعله ذوب گردید , وجوشید .وحتی بدون پسماند شعله ورشد.؛[/FONT]​

​

​

​

” He also observed that it was insoluble in cold and hot water, acetone, Freon 113, ether, petroleum ether, alcohol, pyridine, toluene ethyl acetate, concentrated sulfuric acid, glacial acetic acid, nitrobenzene, isoanyl alcohol, ortho dichlorobenzene, sodium hydroxide, and concentrated nitric acid.[FONT=&quot][/FONT]​

​

[FONT=&quot]اوهمچنین دریافت که آن در آب سرد وگرم ,استون , فرئون 113 ومواد نفتی دیگر نیز حل نمی شود ودر دیگر حلال ها مانند الکل واسیدها و.. [/FONT]​

​

Further tests showed that the substance did not char or melt when exposed to a soldering iron or an electric arc.[FONT=&quot][/FONT]​

​

[FONT=&quot]امتحان های بیشتر نشان داد که این ماده در هنگام همراه بودن با فلز یا آرک الکتریکی ذوب ویا نیمسوز نمی شود .[/FONT]​

​

Moisture did not cause it to rot or swell, prolonged exposure to sunlight did not degrade it, and it was impervious to mold and fungus.
Plunkett’s next step was to duplicate the conditions that had produced the first batch of polymerized tetrafluoroethylene (PTFE).[FONT=&quot][/FONT]​

​

[FONT=&quot]رطوبت باعث خراب شدن یا باد کردن آن نمی شود,قرار گرفتن درمعرض نورآفتاب باعث ضایع شدن آن نمی شود وآن نشت ناپذیر وفاسد نشدنیست. [/FONT]​

​

After experimentation he succeeded in re-creating what had occurred by chance inside the canisters.[FONT=&quot][/FONT]​

​

[FONT=&quot]پس از آزمایشهای متعدد او دریافت که چه چیزی بصورت اتفاقی در قوطی های آزمایشگاه تولید شده است.[/FONT]​

​

On July 1, 1939, he applied for a patent (which he assigned to Kinetic Chemicals) on tetrafluoroethylene polymers. [FONT=&quot][/FONT]​

​

[FONT=&quot]در جولای 1939 او یک پتنت در مورد تترا فلورو پلیمرها تهیه کرد " که به کنتیک شمیکال نصبت داده شده بود" [/FONT]​

​

The patent was granted in 1941.[FONT=&quot][/FONT]​

​

[FONT=&quot]پتنت در 1941پذیرفته شد .[/FONT]​

​

 

[مجتبی ورشاوی2]

جناب asus450000 لطفا مطلبی مناسب رشته ساخت وتولید قرار دهید من با ترجمه مطالب تفلون مشکلی ندارم اما دنبال کردن این مطالب برای سایر دوستان. خسته کننده است .
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Another variation of this approach is a downward lance, shown in Fig. 4-36. Here the
progression is controlled when the lanced tab comes into contact with a spring-loaded stop.
In the next station, the lance is flattened and pushed back into the strip, so that not to
obstruct further progression.
The roller stock pusher (Fig. 4-37) enhances its stock-guiding capacity by combining it
with greater accuracy. The hardened roller, contained at the tip of the unit, contacts the edge
of a material and allows it to slide past by rotating along with its movement. The roller is
held against the material’s edge by the force of a spring, which allows for a width variation
of the strip, rendering any additional adjustment needless.
The material-positioning device (Fig. 4-38) is mounted on the upper half of the die, and
it moves up and down with the movement of the ram. During the downstroke, the long arm
trips over the edge of a sliding block and pushes it toward the edge of the material. The sliding
block, restricted in its movement by a pin, is sandwiched between the die block and the
stripper. The tension adjustment of the slide-pushing arm’s pressure is in the range of 2 to
20 lb (1–10 kg).
4-2-9 Stock Supports, Stock Lifters
Stock-supporting rails, as used in Fig. 4-39a, allow for the strip’s travel above the die surface.
This may be found quite helpful where the height of the strip increases because of
drawing, forming, or other height-altering process.
Stock lifters (Fig. 4-39b) are utilized where the strip is forced down during the die operation
and where its return to the original height is desired. Such need arises with many parts,

altered in height, which travel from station to station, falling into relief recesses during the
operational cycle of the die, from where they are to be pulled up again.
Where the height of a part is not being grossly altered, a lifter-retainer combination, such
as the one shown in Fig. 4-39c, may be used. With the upper half of the die already up, the
lifter is restricted from following along by its travel-limiting flange. When the die slides
down, it exerts a pressure on the lifter as well, forcing it down, along with the strip it retains.

An adjustable version of this type of lifting device is shown in Fig. 4-40. By turning the
slotted head of the unit, its position with regard to the sheet-metal strip as well as its height
can be adjusted. This type of device also takes various sizes of heads, which makes its
adjustability still more versatile.
4-2-10 Stops
Strip material, when first being guided into the die, must stop somewhere for the sequence of
die operations to begin successfully. It is obvious that the strip should not go as far as the forming
tool, which may need some preblanking work performed at the beginning. Advancing the
strip too far may lead to greater than usual wear and tear of the tooling and its subsequent misalignment
and breakage.
For that purpose, stops are introduced in the die work. The first stop, which the strip
meets on its way, is usually the first pierce and blank locator, which navigates the strip in
such a way that all cutting is included prior to its arrival at forming and other stations.
The arrangement shown in Fig. 4-41a has a stop arm placed in the path of an advancing
strip. On reaching the edge of the stop plate, the strip is automatically positioned under the
vital punches, and the whole stop assembly may be pulled out of its way. This little device,
when spring-loaded, snaps forward as the end of the strip leaves the die and is there ready
to stop the next strip to be inserted.
A fixed stop is shown in Fig. 4-41b, where the material can bypass the stop pin’s registration
surface only by being lifted up above its level.
The automatic stop in Fig. 4-41c is a device which slides up and down along with the
movement of the ram and either
• forces the nose of the stop lever up, to release its engagement of the strip for the latter’s
progression (during the downward movement of the ram); or,
• releases its pressure on the lever, thus allowing its nose to come down, pushed by a force
of a spring. In such a position, the lever is ready for registration and retainment of the
advancing strip (during the upward movement of the ram).
A similar device attacheable to the surface of the die block is shown in Fig. 4-42. It is
activated by a spring, which forces the gauge’s nose toward the surface of the die block,
holding it down to register the advancing strip.
A V-notch stop (Fig. 4-43) engages a V-notch cut in the side of the advancing material.
The nose of this device rides on the edge of the strip, snapping forward whenever a
notch is encountered. When filling the notch, the spring force behind the latch pushes the
whole strip material toward the opposite side of the channel, thus locating it under a
punch.

This type of stop is in its origin a finger stop, shown in Fig. 4-44, which is similarly positioned
against the strip’s edge, where it provides the force needed to push the material
against the opposite side. The movement of the finger stop is controlled by a travel-limiting
block or pin, positioned to fit within the relief slot in the stop body itself.
Various alterations of the travel-limiting slot location provide for a wide variety of
applications. The side-located slot may be used with the travel-limiting function of a side
block. The block with a pocket utilizes a pin to control the amount of its movement.
Some miscellaneous stopping ideas are demonstrated in Fig. 4-45. The material-deflecting
pin in Fig. 4-45b makes the material slip over its rounded head, deflecting it down, where it
leaves the die under an angle. The strip, already perforated, it easily averted from its straight
path.

A material stop, allowing for eccentric positioning, is shown in Fig. 4-46. The whole
unit can be rotated around a counterbore and secured in its final position by a steel ball
emerging from its side. The steel ball is pushed out by the movement of a setscrew’s cone
point, which also retains it in the attained position.
The progressing strip stock is stopped in its movement on encountering the springloaded
pin. When pushed down, the pin does not obstruct its advancement, provided there
are no openings in its path.
A cam-operated slide (Fig. 4-47) delivers a fixed amount of adjustment to the sheet-metal
strip. Attached to the upper half of the die, it moves down with the ram, driving the slide block
toward the edge of the material (in its lowest position) and away from the strip (when moving
up).
Electronically controlled material gauging units have a highly controllable area of function.
Good gauging properties of this type of equipment can be made consistent in spite of
variability of material thicknesses and sheet width.
4-2-11 Pressure Pads
Pressure pads are actually small localized strippers, which operate on a slightly different
basis. Instead of stripping parts off the tooling, they eject the pieces by pushing them out of
the tooling.
By bringing the upper part of the die down on the work, as illustrated in Fig. 4-48, the
spring pad is squeezed to its utmost position, up or down, whichever is appropriate. So
restrained, the pad exerts a holding force on the sheet strip, not allowing the material to move
or to be pulled along by the forming or bending action.

During the upstroke of the press, the pad, forced by
the action of its springs shoots forward, ousting the
formed part from within the forming tool. Its opposite
member, a forming block, provides the supportive
action and may or may not contain some ejecting
arrangement, either within its construction or beside
it.
The necessity of additional spring ejecting force is
determined by the shape of a part, by the depth of the
formed section, material type and condition, aside
from other influences.
The retention of the pad in a floating position is
provided by shoulder screws. (Figure 4-49 shows pad
retainers.) These not only secure the block in a relatively
fixed position, they also control the length of its
travel by the amount of space between the counterbore’s
surfaces and the bottoms of their heads. This
space should be equal to the required travel distance,
plus the life of the die.
If necessary, bolt heads may be shimmed for the
proper distance, with some shims being removed during
each sharpening.
In replacement of stripper bolts, which are used
for the retention of spring-loaded blocks, pad retaining
studs may be utilized. These are firmly attached to
the pad by a socket head cap screw. Flat portions on
their body diameter serve in assembly as an area for
wrench application or as key flats protecting against
rotation.

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156 Friction and Friction Models
​

40 µ =​

0.577​

0.5​

file:///C:/DOCUME%7E1/Italy/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image001.gif30​

0.4​

0.3​

20​

​

10​

0-​

−10​

−20​

µ = 0​

0.10​

​

0.20​

file:///C:/DOCUME%7E1/Italy/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image003.jpg​

0.15​

0.12​

0.08​

0.06​

0.05​

0.04​

0.03​

µ = 0.02​

−30
​

0 10 20 30 40​

Height reduction (%)​

file:///C:/DOCUME%7E1/Italy/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image004.gif(c) Discuss the results you obtain. Try to explain the characteristic trends in the friction behavior.​

Alloy	Lubrication	ID after Reduction compression (mm) of ID (%)	µ m
Al-alloy	Dry friction	30.8
	Graphite–oil	38.1
	Teflon foil	37.7
Cu	Dry friction	33.0
	Graphite–oil	37.2
	Teflon foil	38.5
Soft steel	Dry friction	33.9
	Graphite–oil	38.4
	Teflon foil	39.4

10.2 Consider measurement of contact stresses by means of pins extending into the die–workpiece interface during a metal forming application: (a) Apply the two eqs. 10-13 and 10-14 to determine the contact stresses, as well as the Coulomb coefficient of friction, at the location where the mea- surement is done. (The solution is eqs. 10-11 and 10-12.) (b) At a specific location on the surface of a die, the contact stresses were mea- sured to be σ = 40 MPa and τ = 18 MPa. Determine the friction coefficient at this location. 10.3 A cylinder of soft steel was compressed down to an average strain of ε¯ = 1. A thin layer of aluminum foil was used as solid lubricant between the cylinder and the die. Determine the friction factor in the compression process, under the assumption Notes 157 that cylinder and foil are subjected to the same deformation. The flow stress rela- tionships at the actual temperature of compression for the steel specimen and the aluminum foil, respectively, are given as​

σ¯ = Kε¯ n = 715.7 MPa · ε¯ 0.22​

σ¯ = Kε¯ n = 119.3 MPa · ε¯ 0.297​

10.4 In the two graphs presented here, contact stress data from pin measurements performed over the workpiece interface in ring compression are given. The data refer to different locations at the end faces of cylinders of pure Al, compressed down to a height reduction of 10%, for which the shear flow stress was determined to be k = 8 kpsi. Three different conditions of lubrication were investigated: dry friction, condition A; condition B, where a mixture of oleic acid in mineral oil was used as lubricant; and, finally, condition C, where Pb foil was used as a solid lubricant.
file:///C:/DOCUME%7E1/Italy/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image006.jpg​

(Reprinted from Int. J. Mech. Sci., Vol. 1, van Rooyen, G. T., and Backofen, W. A., “A study of the interface friction in plastic compression,” pp. 1–27, 1960 with permission from Elsevier.) (a) Specify the general expressions for shear stress in the cases of (i) Coulomb and (ii) Tresca friction, and define the symbols used. (b) Use the contact stress data in the figure to determine which of the two fric- tion models will describe measured data best for each of the lubricant con- ditions A, B, and C. (c) Calculate the friction factor for lubricant conditions A and B for points at distances r = 0.3 in. and 1.0 in. from the center of the cylinder. NOTES​

1. Wanheim, T., and Bay, N.: “A model for friction in metal forming processes,” Ann.​

CIRP, Vol. 27, No. 1, 1976, pp. 189–193.​

2. Schey, J. A.: “Tribology in Metalworking: Friction, Lubrication and Wear,” ASM Int., Metals Park, Ohio, 1983, pp. 78–79.​

3. Godfrey, D. in Ku, P. M. (Ed.): “Interdisciplinary approach to friction and wear,” NASA Sp-181, Washington, 1968.​

158 Friction and Friction Models​

4. Suthcliffe, M. P. F., Lee, H. R., and Farrugia, D.: “Simulation of transfer layer formation in strip drawing of stainless steel,” Wear, Vol. 254, 2003, pp. 523–531. 5. Male, T., and Cockcroft, M. G.: “A method of the determination of the coefficient of friction of metals under conditions of bulk plastic deformation,” J. Inst. Metals, Vol. 93,
1964–65, pp. 38–46.​

6. Siebel, E., and Lueg, W.: Mitt. Kaiser Wilhelm Inst. Eisenforschung, Vol. 15, 1933, p. 1.​

7. van Rooyen, G. T., and Backofen, W. A.: “A study of the interface friction in plastic compression,” Int. J. Mechanical Sciences, 1960, Vol. 1, pp. 1–27. 8. Hansen, A. W., Welo, T., and Valberg, H.: “A technique for measuring stresses on the tool surface,” Proc. 4th Int. Conf. on Technology of Plasticity, Beijing, China, 1993, Vol. 1, pp. 303–308.
REFERENCES​

Bay, N.: “Modelling and testing of friction in forging,” in “New Developments in Forging​

Technology,” Mat-Info Werkstoff-Informationsgesellschaft, Frankfurt, 2007, pp. 233–252. Lenard, J. G. (Ed.): “Metal Forming Science and Practice,” Elsevier, 2002.​

Mang, T.: “Die Schmierung in der Metallbearbeitung,” Vogel-Buchverlag, 1983.​

Schey, J. A.: “Tribology in Metalworking: Friction, Lubrication and Wear,” ASM Int., Metals​

Park, Ohio, 1983.
file:///C:/DOCUME%7E1/Italy/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image007.gif11 Thermal Effects The energy consumed in a metal forming operation, as, for instance, in a forging stroke, is mainly transformed into heat, which leads to temperature rise in the die and the workpiece. In heavy metal forming equipment, a lot of energy is supplied to the workpiece this way, and there can be substantial global and local heating effects in the workpiece material. In many metal forming applications, there are limits on how high the tempera- ture of the workpiece can rise before one experiences problems such as reduced or unacceptable product quality. This is, for instance, the case in aluminum extrusion, where the maximum temperature of the metal near the outlet from the die should not exceed a certain critical temperature. In this process, material defects, such as surface cracking due to hot tearing of the material, start to appear when this critical temperature is exceeded, and a usable profile can no longer be manufactured. This phenomenon is explained and discussed in this chapter. In addition, it is shown how one can quantify different thermal effects in a metal forming process, such as heating due to plastic deformation inside the workpiece, and heating due to friction over its surface. When the workpiece has higher temperature than the dies, there is cooling against the dies, and the physics required to calculate the cooling is shown for a simple two-dimensional case. It is also explained how the temperature inside the tooling and on the surface of the workpiece can be measured by use of thermocouples. Use of pyrometry to measure the surface temperature on a body is also discussed. Finally, characteris- tic thermal conditions in some typical nonstationary and stationary metal forming processes are described by examples. 11.1 Thermal Effects in Metal Deformation Processes When it comes to thermal effects, heat radiation is in many cases neglected in metal forming applications. But, for instance, hot forming of steels is performed at temper- atures as high as 1000–1200◦C. At these temperatures, loss of heat due to radiation becomes significant and must be included if an accurate thermal analysis is to be done. Al and Al alloys, however, are seldom formed at higher temperature than​

159​

160 Thermal Effects​

Figure 11.1. Energy consumption during deformation of ideal rigid–​

file:///C:/DOCUME%7E1/Italy/LOCALS%7E1/Temp/msohtmlclip1/01/clip_image009.jpg​

plastic material with constant flow stress.
550◦C, and radiation effects are less significant at these low temperatures. They can therefore be neglected without much error.​

If radiation effects and cooling to the surrounding air are neglected, the follow- ing equation1 ,2 can be used to estimate the temperature in a workpiece during a​

metal forming operation:​

T1 = T0 + TD + TF − TT (11-1) Here, the following symbols are used:​

T0 is the initial temperature of the workpiece.​

TD is the temperature increase in the workpiece due to dissipated deformation energy during forming.​

TF is the temperature increase due to friction in the interface between die and workpiece.​

TT is the temperature decrease in the workpiece because of cooling by colder dies.​

11.1.1 Effects Due to Dissipated Deformation Energy​

Consider an ideal rigid–plastic workpiece without strain hardening, i.e., a workpiece of an ideal material with constant flow stress σ¯ .​

The energy added to this workpiece by deformation up to an average strain of​

ε¯(see Fig. 11.1), can be expressed as​

WD = σ¯ε¯V (11-2) Correspondingly, the amount of heat required to give the workpiece the tempera-​

ture rise TD is given by​

QD = cm TD (11-3) In this equation, symbols are​

c (J kg−1K−1), the heat capacity of the workpiece material;​

m, the mass of the workpiece (V is the volume).​

 

[AFSHAR_PIPING]

خاهشااااااااا رییس یه سر به تاپیکتوننننننننننننننن بزنین تا متن مارو هم قبول زحمت کنید.اقا یکی با خبرشون کنه.

 

[مجتبی ورشاوی2]

Another variation of this approach is a downward lance, shown in Fig. 4-36. Here the
progression is controlled when the lanced tab comes into contact with a spring-loaded stop.
In the next station, the lance is flattened and pushed back into the strip, so that not to
obstruct further progression.
The roller stock pusher (Fig. 4-37) enhances its stock-guiding capacity by combining it
with greater accuracy. The hardened roller, contained at the tip of the unit, contacts the edge
of a material and allows it to slide past by rotating along with its movement. The roller is
held against the material’s edge by the force of a spring, which allows for a width variation
of the strip, rendering any additional adjustment needless.
The material-positioning device (Fig. 4-38) is mounted on the upper half of the die, and
it moves up and down with the movement of the ram. During the downstroke, the long arm
trips over the edge of a sliding block and pushes it toward the edge of the material. The sliding
block, restricted in its movement by a pin, is sandwiched between the die block and the
stripper. The tension adjustment of the slide-pushing arm’s pressure is in the range of 2 to
20 lb (1–10 kg).
4-2-9 Stock Supports, Stock Lifters
Stock-supporting rails, as used in Fig. 4-39a, allow for the strip’s travel above the die surface.
This may be found quite helpful where the height of the strip increases because of
drawing, forming, or other height-altering process.
Stock lifters (Fig. 4-39b) are utilized where the strip is forced down during the die operation
and where its return to the original height is desired. Such need arises with many parts,

altered in height, which travel from station to station, falling into relief recesses during the
operational cycle of the die, from where they are to be pulled up again.
Where the height of a part is not being grossly altered, a lifter-retainer combination, such
as the one shown in Fig. 4-39c, may be used. With the upper half of the die already up, the
lifter is restricted from following along by its travel-limiting flange. When the die slides
down, it exerts a pressure on the lifter as well, forcing it down, along with the strip it retains.

An adjustable version of this type of lifting device is shown in Fig. 4-40. By turning the
slotted head of the unit, its position with regard to the sheet-metal strip as well as its height
can be adjusted. This type of device also takes various sizes of heads, which makes its
adjustability still more versatile.
4-2-10 Stops
Strip material, when first being guided into the die, must stop somewhere for the sequence of
die operations to begin successfully. It is obvious that the strip should not go as far as the forming
tool, which may need some preblanking work performed at the beginning. Advancing the
strip too far may lead to greater than usual wear and tear of the tooling and its subsequent misalignment
and breakage.
For that purpose, stops are introduced in the die work. The first stop, which the strip
meets on its way, is usually the first pierce and blank locator, which navigates the strip in
such a way that all cutting is included prior to its arrival at forming and other stations.
The arrangement shown in Fig. 4-41a has a stop arm placed in the path of an advancing
strip. On reaching the edge of the stop plate, the strip is automatically positioned under the
vital punches, and the whole stop assembly may be pulled out of its way. This little device,
when spring-loaded, snaps forward as the end of the strip leaves the die and is there ready
to stop the next strip to be inserted.
A fixed stop is shown in Fig. 4-41b, where the material can bypass the stop pin’s registration
surface only by being lifted up above its level.
The automatic stop in Fig. 4-41c is a device which slides up and down along with the
movement of the ram and either
• forces the nose of the stop lever up, to release its engagement of the strip for the latter’s
progression (during the downward movement of the ram); or,
• releases its pressure on the lever, thus allowing its nose to come down, pushed by a force
of a spring. In such a position, the lever is ready for registration and retainment of the
advancing strip (during the upward movement of the ram).
A similar device attacheable to the surface of the die block is shown in Fig. 4-42. It is
activated by a spring, which forces the gauge’s nose toward the surface of the die block,
holding it down to register the advancing strip.
A V-notch stop (Fig. 4-43) engages a V-notch cut in the side of the advancing material.
The nose of this device rides on the edge of the strip, snapping forward whenever a
notch is encountered. When filling the notch, the spring force behind the latch pushes the
whole strip material toward the opposite side of the channel, thus locating it under a
punch.

This type of stop is in its origin a finger stop, shown in Fig. 4-44, which is similarly positioned
against the strip’s edge, where it provides the force needed to push the material
against the opposite side. The movement of the finger stop is controlled by a travel-limiting
block or pin, positioned to fit within the relief slot in the stop body itself.
Various alterations of the travel-limiting slot location provide for a wide variety of
applications. The side-located slot may be used with the travel-limiting function of a side
block. The block with a pocket utilizes a pin to control the amount of its movement.
Some miscellaneous stopping ideas are demonstrated in Fig. 4-45. The material-deflecting
pin in Fig. 4-45b makes the material slip over its rounded head, deflecting it down, where it
leaves the die under an angle. The strip, already perforated, it easily averted from its straight
path.

A material stop, allowing for eccentric positioning, is shown in Fig. 4-46. The whole
unit can be rotated around a counterbore and secured in its final position by a steel ball
emerging from its side. The steel ball is pushed out by the movement of a setscrew’s cone
point, which also retains it in the attained position.
The progressing strip stock is stopped in its movement on encountering the springloaded
pin. When pushed down, the pin does not obstruct its advancement, provided there
are no openings in its path.
A cam-operated slide (Fig. 4-47) delivers a fixed amount of adjustment to the sheet-metal
strip. Attached to the upper half of the die, it moves down with the ram, driving the slide block
toward the edge of the material (in its lowest position) and away from the strip (when moving
up).
Electronically controlled material gauging units have a highly controllable area of function.
Good gauging properties of this type of equipment can be made consistent in spite of
variability of material thicknesses and sheet width.
4-2-11 Pressure Pads
Pressure pads are actually small localized strippers, which operate on a slightly different
basis. Instead of stripping parts off the tooling, they eject the pieces by pushing them out of
the tooling.
By bringing the upper part of the die down on the work, as illustrated in Fig. 4-48, the
spring pad is squeezed to its utmost position, up or down, whichever is appropriate. So
restrained, the pad exerts a holding force on the sheet strip, not allowing the material to move
or to be pulled along by the forming or bending action.

During the upstroke of the press, the pad, forced by
the action of its springs shoots forward, ousting the
formed part from within the forming tool. Its opposite
member, a forming block, provides the supportive
action and may or may not contain some ejecting
arrangement, either within its construction or beside
it.
The necessity of additional spring ejecting force is
determined by the shape of a part, by the depth of the
formed section, material type and condition, aside
from other influences.
The retention of the pad in a floating position is
provided by shoulder screws. (Figure 4-49 shows pad
retainers.) These not only secure the block in a relatively
fixed position, they also control the length of its
travel by the amount of space between the counterbore’s
surfaces and the bottoms of their heads. This
space should be equal to the required travel distance,
plus the life of the die.
If necessary, bolt heads may be shimmed for the
proper distance, with some shims being removed during
each sharpening.
In replacement of stripper bolts, which are used
for the retention of spring-loaded blocks, pad retaining
studs may be utilized. These are firmly attached to
the pad by a socket head cap screw. Flat portions on
their body diameter serve in assembly as an area for
wrench application or as key flats protecting against
rotation.

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[مجتبی ورشاوی2]

بخش اول
the progression is controlled when the lanced tab comes into contact with a spring-loaded stop.
توالی بوسیله لنسید تب زمانی که با اسپرینگ لود تماس می یابد کنترل می شود
In the next station, the lance is flattened and pushed back into the strip, so that not to
obstruct further progression.
در ایستگاه بعدی لنس پهن است وبه نوار فشار می آورد بنابراین درتوالی کار مشکلی ایجاد نمی کند .
The roller stock pusher (Fig. 4-37) enhances its stock-guiding capacity by combining it
with greater accuracy.
غلطک فشارنده در تصویر بعد - درصورت همراه شدن با صحت در کار میتوان راندمان را بالا برد .
The hardened roller, contained at the tip of the unit, contacts the edge
of a material and allows it to slide past by rotating along with its movement.
غلطک در راس واحد سوار گردیده است با لبه متریال در تماس است و اجازه میدهد با گردش خود ورق نیز در طول جابجا گردد .
The roller is held against the material’s edge by the force of a spring, which allows for a width variation
of the strip, rendering any additional adjustment needless.
نیروی فنر غلطک را در مقابل ورق نگاه میدارد واین مهم برای ورق های مختلف قابل استفاده خواهد بود ولبه های تیز را میگیرد
The material-positioning device (Fig. 4-38) is mounted on the upper half of the die, and
it moves up and down with the movement of the ram.
وسیله جانمایی متریال در شکل بعد با بالا وپایین رفتن رم حرکت میکند ودر بالای دای قرار دارد .
During the down stroke, the long arm trips over the edge of a sliding block and pushes it toward the edge of the material.
در هین نشاندن یک بازوی بلند در بالای بلوک اسلید حرکت می کند وآن را به لبه های متریال می فشارد
The sliding block, restricted in its movement by a pin, is sandwiched between the die block and the
stripper. The tension adjustment of the slide-pushing arm’s pressure is in the range of 2 to
20 lb (1–10 kg).
بلوک اسلید بوسیله یک پین محدود گردیده است که بصورت ساندویچی در بین دای بلوک واستریپر قرار دارد .
میزان کشیدگی بازوهای کشش اسلید درحدود 2 تا 20 ای بی است یعنی یک تا ده کیلو گرم

 

[مجتبی ورشاوی2]

بخش اول ترجمه جناب افشار ...

 

[AFSHAR_PIPING]

بخش اول ترجمه جناب افشار ...

خداوکیلی هرچی از خدا میخای بهت بده خیلی ماهی.خدا رسوندت واسم مهندس.من منتظر بقیه لطفت هستم استاد.

 

[مجتبی ورشاوی2]

ترجمه آقای افشار بخش پایانی "توجه من فرصت اشکال زدایی ندارم زحمتش با خود شما "

 

[dynasty]

سلام دوست عزیز نظرتون رو راجبه ترجمه این جمله میخواستم: مخصوصا اصطلاح no credit is taken

As
mentioned elsewhere no credit is taken for the weld metal cap height or
root penetration bead. Although not often used in aluminium fabrications
because of the need to match joint strength and base metal strength, in
lightly loaded joints a partial penetration joint (Fig. 5.5b), may be acceptable.

 

[مجتبی ورشاوی2]

سلام دوست عزیز نظرتون رو راجبه ترجمه این جمله میخواستم: مخصوصا اصطلاح no credit is taken

As
mentioned elsewhere no credit is taken for the weld metal cap height or
root penetration bead. Although not often used in aluminium fabrications
because of the need to match joint strength and base metal strength, in
lightly loaded joints a partial penetration joint (Fig. 5.5b), may be acceptable.

no credit is taken :برای گرده جوش یا عمق آن نمی شود اندازه ای بیان کرد .(میخواهد بگوید بهش اعتباری نیست ..)

Weld cap hight is the bouffant part of the weld line after welding work.
Weld root penetration means the maximum amount of penetrated weld metal.​

 

[dynasty]

سلام مهندس زحمت اینو میکشی .....

ممنونم پیشاپیش

Many extrusions in aluminium, however, can be produced with the
backing strip incorporated and in this way joint set-up is simplified. It is
possible to design the extrusions with both the backing strip built in and of
such a shape that the joint is self-jigging, as illustrated in Fig. 5.11.
The crevices associated with permanent backing strips result in local
stress concentrations.These may reduce both impact and fatigue resistance
if the root is in a highly stressed area. The crevice may also give rise to
localised corrosion although even in marine environments this has not been
reported as a major problem when the correct alloy has been chosen.
Despite these potential drawbacks, permanent backing strips are a common
feature in many structures used in challenging applications.
Inert gas backing can be used for critical applications such as food processing
or pharmaceutical process pipework or vessels and is very useful
when there is no access to the back of the weld to back-gouge and seal.An
argon purge will prevent oxidation of the root penetration bead and oxide
films being fused into the joint, giving a smooth, even TIG root bead.Typical
designs of backing bars and strips are given in Fig. 5.12.

 

[مجتبی ورشاوی2]

سلام مهندس زحمت اینو میکشی .....

ممنونم پیشاپیش

Many extrusions in aluminium, however, can be produced with the
backing strip incorporated and in this way joint set-up is simplified. It is
possible to design the extrusions with both the backing strip built in and of
such a shape that the joint is self-jigging, as illustrated in Fig. 5.11.
The crevices associated with permanent backing strips result in local
stress concentrations.These may reduce both impact and fatigue resistance
if the root is in a highly stressed area. The crevice may also give rise to
localised corrosion although even in marine environments this has not been
reported as a major problem when the correct alloy has been chosen.
Despite these potential drawbacks, permanent backing strips are a common
feature in many structures used in challenging applications.
Inert gas backing can be used for critical applications such as food processing
or pharmaceutical process pipework or vessels and is very useful
when there is no access to the back of the weld to back-gouge and seal.An
argon purge will prevent oxidation of the root penetration bead and oxide
films being fused into the joint, giving a smooth, even TIG root bead.Typical
designs of backing bars and strips are given in Fig. 5.12.

ترجمه را دوست من در پانویس دانلود کنید ....

 

[alireza_f_kh]

سلام مهندس.خدا قوت

سلام مهندس.خدا قوت

میشه لطفا این متنم ترجمه کنید؟با تشکرمشاهده پیوست ماشينكاري چدن ب&#1.pdf

 

[peyman23]

سلام مهندس شرمندم متن زیر را ترجمه میکنید ممنون
The solar sensor output should be conditioned to adapt the sensor output to the microcontroller
voltage range. The microcontroller produces the inverse bias of photodiodes to
orientate the panels to minimize the current difference. Usually for control purposes, current
signals should be converted to voltage signals. The flowchart in Figure 1.15 presents
the sensor output evaluation and motor control for the sun tracking system [23,24].
For implementation of Equation 1.22, the sensor outputs are added and subtracted by
the differential and adder circuits, respectively. The reference angle (θ) is obtained by the
microcontroller while actual motor positions are also fed back to the microcontroller. The
reference motor positions are achieved by providing the control signals to the motor drive.
Both motors and the drive circuit are powered by a power supply.
The difference signal data are compared with a maximum threshold. If the value is higher,
the sun is misalignedmore than the selected angle. Hence, the reverse action should be taken
by the microcontroller that controls the motor drive.
A differential signal is produced by the difference between generated currents by the
sensors.Movementof not only the sun but also the clouds can affect the output. The presence
of clouds may cause the microcontroller to misinterpret the moving direction of the sun.
This results in moving the platform in the wrong direction and consuming unnecessary
energy. These malfunctions can be eliminated by using intelligent control techniques.
The addition and differentiation of currents are used to identify the real status, that is,
movement of the sun or a passing cloud. To detect cloudpresence, the addition of currents
is used as the parameter, while the difference of currents varies with the movement of the
sun. Addition of currents is not affected by a change in the position of the sun. The addition
of currents is different in cloud, sunset, or sunrise conditions. In the presence of a cloud, the
derivative of current addition is higher than that of sunset or sunrise situations. So, the sun
tracking controller algorithm should consider current difference, current addition, current
evolution slope, and current variations [23].
Analgorithm is required for the determination of sun searching or sun tracking. Sun tracking
is the normal operation while sun searching is required during the presence of clouds.
The flowchart of the algorithm consists of several state machines as shown in Figure 1.16.
The microcontroller is initialized to access the previously recorded data table to decide
to run the sun search, sun tracking, or cloud algorithms. The radiation data table has the
information for a typical cloudless day. The radiation, calculated from these data, is used
to determine whether a cloud has passed over the sensor. The stored information makes it
possible to reproduce the system movement in the case of clouds.
The sun searching or sun tracking states are a function of the radiation. The system will
work in the “sun tracking” state under good meteorological conditions. This state is in
charge of storing the information of the tracking movement. The system movement can be
provided by the microcontroller that provides appropriate switching signals to the motor
drive in order to reach the reference motor positions.
If a cloud is detected, the corresponding state will be “cloud algorithm.” Then, the movement
can be replicated by the stored information in “sun tracking” state. The system remains
in this state until the radiation returns to another value. The cloud is expected to last for
about 15 min. When this time is over, the system will look for the sun and maximum
radiation. This temporal limitation is used to minimize the error due to the approximation.
The sun’s movement is characterized by azimuth and elevation angles. Depending on
the time of day, the azimuth or elevation angle changes in a different way. For example,
early in the morning, the elevation angle changes steeply and the azimuth angle almost
remains constant. The main state selection is based on the addition voltages, because radiation
is calculated from these data. Once the state is selected, the fundamental variable is
the differential voltage. These data are sampled to know the sun’s movement in the “sun
tracking” state. The “sun search” state is in charge of orientating the sensor toward the
sun if partial sunlight is available due to clouds. This action is necessary in certain conditions,
for example, at dawn, and to orientate the sensor after the “cloud algorithm” state.
In this state the movement of the platform is bidirectional to prevent malfunction of the
system

 

[sash1367]

سلام مهندس خدا بهت سلامتی بده
یه زحمتی بکش بگو چه جوری زبان یاد گرفتی
منی که هیچ چیز از زبان نمیفهمم چجوری باید یاد بگیرم
ممنون

 

[مجتبی ورشاوی2]

سلام مهندس شرمندم متن زیر را ترجمه میکنید ممنون
The solar sensor output should be conditioned to adapt the sensor output to the microcontroller
voltage range. The microcontroller produces the inverse bias of photodiodes to
orientate the panels to minimize the current difference. Usually for control purposes, current
signals should be converted to voltage signals. The flowchart in Figure 1.15 presents
the sensor output evaluation and motor control for the sun tracking system [23,24].
For implementation of Equation 1.22, the sensor outputs are added and subtracted by
the differential and adder circuits, respectively. The reference angle (θ) is obtained by the
microcontroller while actual motor positions are also fed back to the microcontroller. The
reference motor positions are achieved by providing the control signals to the motor drive.
Both motors and the drive circuit are powered by a power supply.
The difference signal data are compared with a maximum threshold. If the value is higher,
the sun is misalignedmore than the selected angle. Hence, the reverse action should be taken
by the microcontroller that controls the motor drive.
A differential signal is produced by the difference between generated currents by the
sensors.Movementof not only the sun but also the clouds can affect the output. The presence
of clouds may cause the microcontroller to misinterpret the moving direction of the sun.
This results in moving the platform in the wrong direction and consuming unnecessary
energy. These malfunctions can be eliminated by using intelligent control techniques.
The addition and differentiation of currents are used to identify the real status, that is,
movement of the sun or a passing cloud. To detect cloudpresence, the addition of currents
is used as the parameter, while the difference of currents varies with the movement of the
sun. Addition of currents is not affected by a change in the position of the sun. The addition
of currents is different in cloud, sunset, or sunrise conditions. In the presence of a cloud, the
derivative of current addition is higher than that of sunset or sunrise situations. So, the sun
tracking controller algorithm should consider current difference, current addition, current
evolution slope, and current variations [23].
Analgorithm is required for the determination of sun searching or sun tracking. Sun tracking
is the normal operation while sun searching is required during the presence of clouds.
The flowchart of the algorithm consists of several state machines as shown in Figure 1.16.
The microcontroller is initialized to access the previously recorded data table to decide
to run the sun search, sun tracking, or cloud algorithms. The radiation data table has the
information for a typical cloudless day. The radiation, calculated from these data, is used
to determine whether a cloud has passed over the sensor. The stored information makes it
possible to reproduce the system movement in the case of clouds.
The sun searching or sun tracking states are a function of the radiation. The system will
work in the “sun tracking” state under good meteorological conditions. This state is in
charge of storing the information of the tracking movement. The system movement can be
provided by the microcontroller that provides appropriate switching signals to the motor
drive in order to reach the reference motor positions.
If a cloud is detected, the corresponding state will be “cloud algorithm.” Then, the movement
can be replicated by the stored information in “sun tracking” state. The system remains
in this state until the radiation returns to another value. The cloud is expected to last for
about 15 min. When this time is over, the system will look for the sun and maximum
radiation. This temporal limitation is used to minimize the error due to the approximation.
The sun’s movement is characterized by azimuth and elevation angles. Depending on
the time of day, the azimuth or elevation angle changes in a different way. For example,
early in the morning, the elevation angle changes steeply and the azimuth angle almost
remains constant. The main state selection is based on the addition voltages, because radiation
is calculated from these data. Once the state is selected, the fundamental variable is
the differential voltage. These data are sampled to know the sun’s movement in the “sun
tracking” state. The “sun search” state is in charge of orientating the sensor toward the
sun if partial sunlight is available due to clouds. This action is necessary in certain conditions,
for example, at dawn, and to orientate the sensor after the “cloud algorithm” state.
In this state the movement of the platform is bidirectional to prevent malfunction of the
system

سلام دوست من لطف کن ومطالب در ارتباط با ساخت وتولید درخواست کن .
با اینحال در اولین فرصت مطلب را برایت ترجمه میکنم

 

[مجتبی ورشاوی2]

سلام مهندس خدا بهت سلامتی بده
یه زحمتی بکش بگو چه جوری زبان یاد گرفتی
منی که هیچ چیز از زبان نمیفهمم چجوری باید یاد بگیرم
ممنون

چی بگم والا ..
کافیه هر روز با آن سر وکار داشته باشی ..
هر یگ روز یک پاراگراف
هر هفته یک صفحه
هر سال یک کتاب

 

[مجتبی ورشاوی2]

میشه لطفا این متنم ترجمه کنید؟با تشکرمشاهده پیوست 91537

ترجمه مطلب شما را آغاز کردم
متاسفانه مدتی بود توجهی به این تایپیک نداشتم شرمنده....

 

[alireza_f_kh]

اتفاقا که چقدرم عجله داشتم.خدا خیرت بده.دمت گرم مهندس.الان دارم میرم حرم امام رضا واست دعا می کنم.

 

[مجتبی ورشاوی2]

اتفاقا که چقدرم عجله داشتم.خدا خیرت بده.دمت گرم مهندس.الان دارم میرم حرم امام رضا واست دعا می کنم.

بخش اول ترجمه آماده است :
موضوع :بررسی پیرامون قابلیت ماشینکاری چدن داکتیل با دستگاه وایرکات مشاهده پیوست Manuf Technol-1.doc
تغییرات بعدی وادامه ترجمه بزودی .
لطفا نظرات خود را برای بهتر شدن ترجمه بیان کنید .
باتشکر