Why doesn’t anything stick to Teflon? - Ashwini Bharathula
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.
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.
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
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.
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,
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."
