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2017年
01月05日
20:09 bbbcさん

Ted-Ed1701 Why doesn't anything stick to Teflon?       (なぜテフロンには何もくっつかないのか )

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「テフロン」は米デュポン社の商標。 一般名は「フッ素樹脂」(FとCの高分子化合物)。
結合が強固のため、他の物質を寄せ付けず、結果、摩擦係数が非常に低い。
フライパンは特に有名。 強火は注意、空焚きは厳禁。(有毒ではないよう)

学習用 対訳付き動画⇒http://tededjphukyu.webcrow.jp/Translation.html?654

 05分 155wpm    

字幕:開始後 で字幕On/Off、 で言語選択。文字サイズはオプションから。

下記英文は ブラウザ Chrome のマウスオーバー辞書が使えます。

Nothing stuck to Mafia boss John Gotti who evaded justice for years by bribing and threatening jurors and witnesses. That earned him the name the Teflon Don after one of the slipperiest materials on Earth.
 John Gotti(1940-2002):実在したマフィアのボス。罪逃れが巧妙で あだ名がテフロン

Teflon was in the spacesuits the Apollo crew wore for the moon landing, in pipes and valves used in the Manhattan Project, and maybe in your kitchen as the nonstick coating on frying pans and cookie sheets. So what is this slippery solid, and why doesn't anything stick to it?

Teflon is a brand name for polytetrafluoroethylene, or PTFE. It was stumbled upon accidentally in 1938 by a 27-year-old American chemist named Roy Plunkett while he was trying to develop a non-toxic refrigerant fluid for DuPont, a chemicals company. The strange, white substance that formed inside his lab canister was chemically inert, meaning it wouldn't react with other substances.
 polytetrafluoroethylene, or PTFE::フッ素樹脂 (正しくは四フッ化エチレン樹脂)

It also had an extremely low coefficient of friction, making other materials slide right off it. Teflon's properties make it perfect when you need something slippery, chemical resistant, or waterproof, which means it has a lot of applications. It can be found all over the place, as a coating on raincoats, industrial ball bearings, artificial joints, circuit boards, and even the Rocky Mountains-themed roof of the Denver International Airport.

The incredible properties of PTFE come from its molecular structure. It's a polymer, meaning it's made of long chains of repeating units of atoms strung together. A PTFE chain has a backbone of carbon atoms, each of which is attached to two fluorines. The fluorine atoms surround the carbon like armor, spiraling around the chain, and the bond between carbon and fluorine is incredibly tight. Like a couple that ignores everyone except each other, carbon and fluorine interact so strongly that the normal, intermolecular forces that help substances stick to each other don't stand a chance.

Even the famously adhesive feet of geckos(ヤモリ) usually can't get a grip. But wait!
If PTFE doesn't stick to anything, how can it be so firmly attached to something like a pan? One method involves sandblasting the pan or etching it with chemicals to make it rough. Then, a special primer is applied, which acts like glue. Its exact composition is a trade secret guarded by each manufacturer. The pan is sprayed with liquid PTFE and heated to around 800 degrees Fahrenheit. (約430℃)

The layers then solidify into a smooth, slick coating. When you later cook eggs in this PTFE-coated pan, the extra tight carbon-fluorine bonds just ignore the water and fat and protein molecules in the eggs. Without those interactions, the food just slides around without sticking.

You might wonder if it's safe to cook in a PTFE-coated pan. The answer is yes, if you're careful. PTFE is stable at moderate temperatures, like you'd use to cook eggs or fish, but above 500 degrees Fahrenheit(260℃), it starts to degrade, and heating it further releases fumes that can make you feel sick. An empty pan can reach 500 degrees fast over high heat, but most kitchens are ventilated well enough to dissipate the fumes.

People used to also think that accidentally consuming PTFE that flaked off a scratched pan was bad for you, but the current consensus is that it's harmless. Because PTFE doesn't interact with other chemicals very well, it isn't thought to break down inside your body.

Whether it's safe to manufacture Teflon is another story. DuPont and its spin-off company Chemours now face lawsuits worth millions of dollars. They've been accused of polluting the environment for decades and exposing employees and local communities to health risks associated with a toxic chemical called PFOA. That chemical was involved in manufacturing Teflon.

As for John Gotti, in 1992, the Mob boss was finally convicted of five counts of murder, among other charges. That prompted the head of the FBI office in New York City to announce, "The Teflon is gone. The Don is covered in Velcro, and all the charges stuck."
 Velclo:ベルクロ、面ファスナーの米商標(日本ではクラレがマジックテープの商標)
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