Ah, shower thoughts: those sudden flashes
of profound wisdom and insight that strike when we least expect them. Does a straw have one hole or two? If a tomato is a fruit, is ketchup a smoothie? Why do they package croutons in sealed bags;
aren’t they already stale bread? If nothing sticks to Teflon, how does Teflon
stick to frying pans? While sadly many of these questions don’t
have definite answers, the last one fortunately does. So turn on your cooking range, tell your roommate
to shut up about their precious cast-iron frying pan, and join us as we dive into the
surprisingly fascinating history of Teflon and non-stick cookware. The story of Teflon begins in 1938 with American
chemist Roy J. Plunkett. Born in 1910 in New Carlisle, Ohio, Plunkett
studied chemistry at Ohio State University, where he earned his PhD in 1936 for his thesis
on carbohydrate oxidation. Upon receiving his doctorate, he went to work
as a research scientist at the E.I. du Pont de Nemours and Company’s Jackson
Laboratory in Deepwater, New Jersey. Plunkett’s first assignment at DuPont was
to investigate a family of gases called chlorofluorocarbons as potential refrigerants. At the time, most refrigeration systems ran
on highly-toxic substances like sulfur dioxide and ammonia, which leaked and killed dozens
of people every year. As part of his research, Plunkett and his
assistant, Jack Rebok, prepared a gas called tetrafluoroethylene or TFE and stored it in
small cylinders on dry ice prior to treating it with hydrochloric acid. On April 6, 1938, the pair loaded one of these
cylinders into their experimental apparatus, opened the valve and…nothing happened. No gas escaped the cylinder, even though its
weight suggested that it was still full. Puzzled, Plunkett removed the valve and inverted
the cylinder, causing some white powder to fall out. He stated of this, “We scraped around some
with [a] wire inside the cylinder… to get some more of the powder. What I got out that way certainly didn’t
add up, so I knew there must be more inside.” Plunkett thus proceeded to saw the cylinder
in half, revealing its walls to be coated with a white, dense, slippery substance. The TFE had spontaneously polymerized into
polytetrafluoroethylene, or PTFE, with the steel walls of the cylinder acting as a catalyst
for the reaction. Testing revealed that this substance had remarkable
qualities: it was chemically inert, repelling and resisting nearly all known solvents; heat
resistant; electrically insulating; and very, very, slippery. Indeed, the Guinness Book of World Records
once listed Teflon as the substance with the lowest known coefficient of friction, and
it is the only substance to which a gecko lizard’s feet will not stick. (More on the fascinating reason why not in
the Bonus Facts in a bit) While his colleagues saw his experiment as
a failure, Plunkett immediately suspected PTFE might have many unique applications. Unfortunately, he was soon transferred to
DuPont’s leaded gasoline division, and it fell to others to reveal the new substance’s
full potential. Thankfully, the timing couldn’t have been
better, for PTFE immediately proved itself the perfect solution to a crucial wartime
problem. When the Manhattan Project to develop the
first atomic bomb was launched in 1942, only one substance was known to be capable of sustaining
nuclear fission: Uranium-235, an isotope that makes up only 0.72% of natural Uranium. The project thus had to process and enrich
tons upon tons of Uranium ore to scrape together enough U-235 to build a bomb. This gargantuan task was carried out at Oak
Ridge, Tennessee, where three different enrichment methods were used in parallel. The first, known as thermal diffusion, was
used at Oak Ridge’s S-50 plant and exploited the different speeds at which U-235 and the
heavier and more abundant isotope U-238 rose in a column of heated liquid. The second method, the calutron, was used
at the Y-12 plant and was essentially a giant mass spectrometer; Uranium was vaporized into
charged ions, accelerated, and passed by a strong magnetic field. The two isotopes would be deflected by different
amounts and separate into two beams, which could be collected separately. The third and final enrichment method was
known as gaseous diffusion, and was carried out at the massive K-25 plant - at 489,000
square metres one of the largest structures ever built. In this process, Uranium was converted into
Uranium Hexafluoride gas and passed through multiple cascades of semi-permeable membranes. As the lighter U-235 diffused through the
membranes faster than U-238, after every cascade the gas became increasingly enriched with
the fissile isotope. But while the process worked in theory, there
was a major practical problem: Uranium Hexafluoride is extremely reactive, and tends to corrode
and dissolve most metals. Fortuitously, the recently-discovered PTFE
was impervious to the gas, and was used not only to make the vital diffusion membranes
but also to line all the pipes and valves in the K-25 plant. This was the substance’s first major application,
and allowed the Manhattan Project to produce enough enriched Uranium to complete Little
Boy, the bomb dropped on Hiroshima on August 6, 1945. In that same year, Kinetic Chemicals, a partnership
between DuPont and General Motors, trademarked PTFE under the now ubiquitous name Teflon. Despite its successful use in the Manhattan
Project, up until this point Teflon had been expensive to produce and difficult to shape
into useful products. But DuPont chemists soon developed new formulations
and manufacturing methods to make Teflon easier to mould and extrude, and in 1950 the company
built its first dedicated Teflon plant in Parkesburg, West Virginia. At first the substance was mainly used for
coating machined metal parts and making chemical-resistant seals and gaskets, but soon DuPont expanded
into Teflon-coated baking pans, conveyor belts, and blades for industrial bakeries and kitchens. While non-stick home cookware like frying
pans should have been a logical next step, Testing had revealed that at temperatures
above 320 degrees Celsius (about 600 degrees Fahrenheit), Teflon began to soften and release
mildly toxic gases. While this was not a major issue for baking
ware, it could potentially cause problems at stovetop temperatures. DuPont was thus wary of allowing the average
consumer to use Teflon until it had been declared completely safe. As a result, they were beaten to this highly
lucrative market by an enterprising couple from France. In 1954, Marc Grégoire, an engineer at the
French National Office for Aerospace Research or ONERA, was experimenting with using Teflon
to coat the moulds for fibreglass fishing rods. On learning of his research, his wife Colette
urged him to use Teflon to create non-stick cookware like frying pans. After perfecting and patenting the coating
process, the Grégoires set up a successful home-based business, with Marc coating the
pans at home and Colette peddling them on the streets. French chefs snapped up the amazing new pans,
and by 1956 the Grégoires had made enough money to open their own factory, producing
non-stick cookware under the brand-name Tefal - a contraction of “Teflon” and “Aluminium”. That same year the French health authorities
declared that Teflon presented no health hazard, while in 1958 the French Ministry of Agriculture
approved the use of Teflon in food processing. By 1960, the Tefal factory was producing over
3 million units per year. Realizing that they were losing out on a valuable
market, DuPont sought approval from the FDA to use Teflon in cookware and food processing
equipment. But while this approval was granted in January
1960, DuPont still moved slowly, seeing non-stick cookware as a lesser priority. It was not until an American businessman named
Thomas Hardie began importing Tefal cookware from France that the newfangled product began
to take off in the United States. Hardie became the new evangelist of non-stick
cookware, importing millions of French-made frying pans and building his own factory in
Timonium, Maryland in 1961. That same year, another entrepreneur named
Marion Trozzolo, founder of Laboratory Plasticware Fabricators, introduced a rival American-made
nonstick pan under the brand name “The Happy Pan.” Unfortunately, Hardie and Trozzolo’s hard
work and enthusiasm soon backfired, as other cookware manufacturers began producing their
own non-stick products, flooding the market. As American chemists had less experience with
Teflon coatings than their French counterparts, many of these imitators were inferior to the
Tefal originals, turning many American consumers away from the idea of non-stick cookware. In response, DuPont launched a massive research
campaign to improve their product, and in 1968 launched their own line of nonstick frying
pans featuring their more scratch-resistant “Teflon II” formulation. Teflon cookware has been a staple of the American
kitchen ever since. So how do they actually get the Teflon to
stick to the pans? This apparently impossible feat involves two
main processes, one mechanical and one chemical. Prior to being coated, nonstick cookware is
sandblasted to create a rough surface full of tiny nooks and crannies. The Teflon coating is then heated to its softening
point and pressed into place so that it flows into these openings and hardens, creating
what are effectively millions of tiny dovetail joints that hold the coating firmly in place. But while this pre-roughening is typically
enough to ensure the Teflon doesn’t slide or peel off, the Teflon itself can also be
made stickier via a number of chemical processes. What makes Teflon so slippery and chemically
inert is the presence of the element Fluorine, which is extremely electronegative and holds
tightly to its electrons, preventing it from reacting with other elements. Bombarding the Teflon coating with high-voltage
plasma prior to application - a process called corona discharge treatment - strips away some
of these Fluorine atoms, allowing them to be replaced with other elements like oxygen
that bond more readily to the metal pan. This safe effect can also be accomplished
using chemicals known as reducing agents. But moving on from pans, as alluded to previously,
while Teflon is most commonly associated with nonstick cookware, this remarkable substance
has near limitless applications. It is used in industry as a lubricant, an
electrical insulator, and to make chemically resistant seals, coatings, and liners; in
medicine as an inert, antibacterial coating for catheters and implants like artificial
heart valves; and in fashion to create water and stain-repellent fabrics. It even played a vital role in landing men
on the moon. On February 1, 1967, the crew of Apollo 1,
the first planned test flight of the Apollo Spacecraft, perished in a fire during a training
exercise on the launch pad. A major factor in the accident was the extensive
use of nylon and other polymers in the spacecraft and the astronauts’ pressure suits, which
in the pure oxygen environment of the cabin burned with explosive ferocity. To avoid a repeat of Apollo 1, NASA developed
a new material called beta cloth, consisting of glass fibres coated with Teflon and woven
into fabric. Not only was beta cloth fire resistant, only
melting at temperatures above 650 degrees Celsius, but it also reflected solar radiation
well and was resistant to micrometeorite strikes, making it ideal for the outer covering of
the Apollo astronauts’ EVA suits. Teflon’s extremely low coefficient of friction
also lends itself well to applications where any other material would fail. In 1993, Canada began construction of the
Confederation Bridge across the 13 kilometre Northumberland Strait, linking the provinces
of New Brunswick and Prince Edward Island. The bridge was assembled from 175 prefabricated
cast-concrete sections weighing 7,500 tons each. To move these massive pieces from the staging
area to the pier and the crane ships that would drop them into place, engineers used
special crawlers running on custom-designed rails coated with - you guessed it - Teflon. Yet despite its many applications, Teflon
does have a dark side, and has been at the centre of several public health controversies
over the years. As early as the 1950s, when Teflon was first
manufactured in large quantities, reports emerged that DuPont employees exposed to fumes
from overheated Teflon suffered temporary flu-like symptoms or even tremors. While these rumours were found to be overblown,
it nonetheless stoked a public distrust of Teflon products that would persist into the
1980s. However, until 2013, consumer-grade Teflon
was manufactured using a chemical called perfluorooctanoic acid or PFOA, used as an anti-clumping agent. PFOA exposure has not only been linked to
testicular, kidney, thyroid, prostate, bladder, and ovarian cancer, but the chemical degrades
very slowly and persists in the environment for decades. While ordinary cookware contains negligible
amounts of PFOA, a 2005 class action lawsuit revealed that over the decades DuPont factories
knowingly dumped thousands of tons of the chemical into public waterways. In 2017, the company was ordered to pay a
$671 million settlement to 3,500 plaintiffs who claimed to have contracted various cancers
and other diseases due to this environmental contamination. And if this story sounds familiar, it’s
because it formed the basis for the 2019 film Dark Waters starring Mark Ruffalo. Overall, however, the impact of Teflon on
humanity has generally been considered to be more positive than negative, such that
in 1951 the city of Philadelphia awarded its discoverer, Roy Plunkett, the John Scott Medal
for contributions to the “comfort, welfare, and happiness of human kind.” Appropriately, those in attendance at the
awards ceremony received complimentary Teflon-coated muffin tins. For his accomplishments he was also inducted
into the Plastics Hall of Fame in 1973 and the National Inventors’ Hall of Fame in
1985. Bonus Fact: So why is Teflon the only known thing a gecko’s
feet can’t stick to? Gecko's have millions of tiny hairs on their
toes called setae. All combined, these hair-like tissues give
a washboard type appearance to a gecko's toes. Each one of these seta have thousands of thinner
hair-like structures that have flat caps at the ends called spatulae. These spatulae use what is called "van der
Waals" force to allow the gecko's feet to adhere to objects. More specifically, all of these seta and spatulae
combined give the gecko's feet an extremely large surface area, compared to its size. This surface area allows the gecko to take
advantage of attraction caused by van der Waals force. Van der Waals force, simply stated, is the
combined attractive forces between molecules. Normally, the force between molecules is too
minute to matter; however, given the light weight nature of a gecko (approximately 2.5
ounces) and the extreme number of spatulae (which are about the size of a bacterium),
the combined force allows the gecko to "stick" to almost anything. This surface area is so great that it has
been shown that if a mature gecko were to have all of their setea in contact with a
surface at one time, it could potentially support up to 290 lbs. This brings us to Teflon, which as noted is
mainly carbon and fluorine. Fluorine itself again as noted is highly electronegative,
meaning it really, really likes to attract electrons to itself. Because of this, it tends to mitigate what
is known as the "London dispersion force". This force is thought to usually be the dominate
player in the van der Waals force. Thus, a gecko, who is dependent on the sum
total of all of the factors of van der Waals force, would find it extremely difficult to
stick to anything that eliminates its ability to utilize this force. As such, geckos cannot "stick" to Teflon. And just as another fun gecko fact, most geckos
lack a moveable eyelid. Instead, they use their tongue to help keep
their eyes clean and moisturized.
