What is Gore-tex®?
Paul Goettlich/Mindfully.org 4jun2005
[More on Teflon]
This article came about after searching for a pair of hiking boots that have sufficient treads to hold
me on steep mountain paths.
At a popular outdoor and camping store in Berkeley, I found that about 90% of the boots had a Gore-tex®
hang-tag on them. About a quarter of them were treated with an unspecified antimicrobial, or bacterial
agent. I didn't want either because I get a rash from Gore-tex® fabric and I surely didn't want a
pesticide next to my body, which antimicrobials and antibacterials are classified as. I had to act
fast because my breathing is affected by the great amount of noxious chemicals in sporting goods
stores. A noxious chemical is one that is irritating or offensive and that may have a harmful effect
on life.
In spite of the fact that many people are highly sensitive to harmful chemicals, they shouldn't feel
like freaks. In fact, I am grateful that my body alerts me to these hidden dangers and think that
readers of this article should feel the same way. However, sales people can feel otherwise after our
concerns are expressed. They may suggest we go to a place that specializes in "Berkeley sort of
stuff," essentially meaning that the desire is fringe. I admit it I am rare in my concern about
Gore-tex® in comparison to 99.99% of any selection of shoppers in the US. But why would I want
to agree with a group of people — no matter how large or prevalent in society — that assumes the
safety of most of what industry feeds them, clothes them in and houses them in? My own frustration
grows as it is rapidly becoming difficult to purchase clothes that don't contain some form of
synthetic chemical as a part of the weave; or as a fabric treatment for any number of stated purposes.
Nanoparticles are rapidly taking hold as well.
So, what is Gore-tex®?
Essentially Gore-tex® is a Teflon®-treated synthetic polymer — a plastic. Teflon® is a
brand name for tetrafluoroethylene / polytetrafluoroethylene (PTFE). Generally, all plastics are
made by the process of combining many toxic chemicals into long chain molecules called polymers
using great heat and pressure. The process is never 100% perfect, meaning that there are always
toxic chemicals that leach or migrate into whatever comes into contact with them — food, drink,
air and you. Teflon® is no different. Make no doubt about it, Teflon® does leach toxic
chemicals into whatever contacts it. According to a Russian study in 1978, in water that had
contacted the material, fluor ions and organofluorine compounds were detected. (1) In another
study, benzene was found.(2)
More technically, Gore-tex® is a dispersion-polymerised PTFE that is patented by
W. L. Gore and Associates. It is classed as a stretched semi-crystalline film, and is produced
by extrusion under stress (faster take-up rate than extrusion rate). The extrudate is stretched
below the melting temperature, often in the presence of an aromatic hydrocarbon that swells the
amorphous region, creating porosity. The hydrophobic nature of the PTFE means that liquid water
is repelled from the pores, whereas water vapour can pass through. It is important to realise
that once the PTFE pores are filled with liquid water, the fabric can allow liquid water to pass
though until it is dry again. Thus Gore-tex®-containing fabrics (such as Nomex/Gore-tex,
which consists of an outer aramid(3) fabric, a central Gore-tex® layer, and a cotton backing)
should never be used as protection from chemicals as many will pass straight through. Any water-
miscible solvent (eg alcohol) can fill the pores, and then liquid water can displace it and
continue to rapidly pass through until the fabric is fully dried out.(4)
Gore-tex® is a proprietary teflonized Teflon® is the brand name of a polymer compound
discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial
product in 1946.
Teflon is polytetrafluoroethene (PTFE®).
Teflon® is also used as the trade name for a polymer with similar properties, perfluoroalkoxy
polymer resin (PFA®)
History:
W.L. Gore & Associates, Inc. was founded in 1958 by Wilbert L. "Bill" Gore and his wife, Genevieve
Gore, in Newark, Delaware. Bill Gore was a DuPont research chemist working in fluropolymers, and
based on a suggestion by his son, Robert W. "Bob" Gore, he developed and patented a process for
insulating wires with Teflon® (DuPont's trade name for PTFE®). A decade later, Bob invented
Gore-Tex®, an expanded form of PTFE®, and the company today makes a wide range of products
in the medical, industrial, electrical and fabrics fields all based on his core PTFE® membrane
technology invention.
Gore-tex® patent: U.S. Pat. 3,962,153 (8 June 1976) R.W.Gore (to W.L.Gore and Associates).
This is a continuation-in-part of application Ser. No. 39,753, filed May 21, 1970, now abandoned.
source: U.S. Patent Office 4jun2005
References
1. Proklina et al, Hygenic evaluation of polymeric materials intended for use in the food industry, Gig.
Sanit., 1, 111, 1978
2. Jickells et al, Gas chromatographic/mass spectrometric determination of benzene in nonstick cookware
and microwave susceptors and its migration into foods on cooking, J. AOAC Int., 76, 760, 1993.
3. An aramid is an aromatic polyamide fibers characterized by excellent high-temperature, flame-resistance,
and electrical properties. Aramid fibers are used to achieve high-strength, high-modulus reinforcement
in plastic composites. Aramid fiber (1961) is a synthetic fiber, a fire-resistant polyamide, is a
favorite for aerospace and military; bullet-proof protective "armor" fabric, as well as an asbestos
substitute. A well-known type of aramid fiber (a para-aramid) is commonly known by its DuPont trade
name, Kevlar®.
Aramid fiber characteristics:
Sensitive to degradation from ultraviolet radiation; good
resistance to abrasion, chemical degradation, and thermal degradation; nonconductive; no melting
point; low flammability; good fabric integrity at elevated temperatures; para-aramid fibers such as
Kevlar and Twaron, which have a slightly different molecular structure, also provide outstanding
strength-to-weight properties, high tenacity and high modulus.
Major industrial uses:
Flame-resistant clothing; protective vests and helmets; composites; asbestos
replacement; hot air filtration fabrics; tire and mechanical rubber goods reinforcement; ropes and cables;
sail cloth (not necessarily racing boat sails); sporting goods; drumheads.
Production:
The Federal Trade Commission definition for Aramid fiber is "A manufactured fiber in which the fiber-forming
substance is a long-chain synthetic polyamide in which at least 85 percent of the amide linkages are attached
directly to two aromatic rings." Aramid fiber is produced by spinning a solid fiber from a liquid chemical blend.
This relies on a co-solvent with an ionic component (calcium chloride) to occupy the hydrogen bonds of the amide
groups, and an organic solvent (N-methyl pyrrolinidone) to dissolve the aromatic polymer; prior to DuPont's
invention of this process, no practical means of dissolving the polymer was known. First U.S. Commercial
Aramid Fiber Production: 1961, DuPont Company. Current U.S. Aramid Fiber Producers: INVISTA
(source: Wikipedia 4jun2005)
In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of
atoms, which are alternately singly and doubly bonded to one another. (More properly, these bonds may be seen
as a hybrid of a single bond and a double bond, each bond in the ring being identical to every other.) This
commonly seen model of aromatic rings was developed by Friedrich August Kekulé von Stradonitz. The model for
benzene consists of two resonance forms, which corresponds to the double and single bonds switching positions.
(source: Wikipedia 4jun2005)
Teflon® is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in
1938 and introduced as a commercial product in 1946.
Teflon is polytetrafluoroethylene (PTFE)®.
F F
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R - C - C - R
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F F
Teflon is also used as the trade name for a polymer with similar properties, perfluoroalkoxy polymer resin (PFA):
F F F F
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R - C - C - C - C - R
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F F F O
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F - C - F
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F
Teflon® has the lowest coefficient of friction of any solid material known to man. It is used as a non-stick coating
for pans and other cookware. Teflon® is very unreactive, and so is often used in containers and pipework for
reactive chemicals. Its melting point varies between 260 °C (FEP)® and 327 °C (PTFE)®, depending on which
specific teflon resin is being discussed.
Teflon® is sometimes said to be a spin-off from the US space program with more down-to-earth applications; this is
an urban legend, as teflon® cooking pans were commonplace before Yuri Gagarin's flight in 1961. PTFE® was
discovered serendipitously by Roy Plunkett of DuPont in 1939, while attempting to make a new CFC refrigerant.
DuPont patented it in 1941, and registered the Teflon® trademark in 1944.
Its first significant use was in the Manhattan Project, as a material to contain highly-reactive uranium hexafluoride,
when it was known as K416.
It was first sold commercially in 1946 and by 1950, DuPont® was producing over a million pounds (weight) per year
in Virginia.
Teflon® has been supplemented with another DuPont® product, Silverstone, a three-coat fluoropolymer system
that produces a more durable finish than Teflon®. Silverstone was released in 1976.
Amongst many other industrial applications, Teflon® is used to coat certain types of hardened, armour-piercing
bullets, so as to reduce the amount of wear on the firearm's rifling. These are often mistakenly referred to as
"cop-killer" bullets on account of Teflon's® supposed ability to ease a bullet's passage through bullet-proof
armour. Any armour-piercing effect is, however, purely a function of the bullet's velocity and rigidity rather than
a property of Teflon®.
Teflon® exposure has been implicated in cancer, though DuPont® denies any association. Non-stick coatings on
household frying pans have also been shown to release toxic gases upon overheating. These gases are lethal to avians,
and can cause flu-like symptoms in humans.
Teflon has excellent electrical properties especially at radio frequencies, making it eminently suitable for use as
an insulator in cables and connector assemblies. Combined with its high melting temperature this makes it the material
of choice as a high performance substitute for the weaker and more meltable polythene that is commonly used in
low-cost applications. (source: Wikipedia 4jun2005)
4. http://www.nvon.nl/scheik/best/faq's/science%20chemistry/scichem-faq.pdf 4jun2005
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