Polytetrafluoroethylene or PTFE (more
commonly known as Teflon) is a particularly versatile ivory-white and opaque
plastic fluoropolymer; it is made by the free-radical polymerisation of many
tetrafluoroethene molecules, and is suitable for a wide range of applications
in industries as diverse as aerospace, the food and drink industry,
pharmaceuticals and telecoms.
Produced by AFT Fluorotec in rods or tubes
of any size, or filled with glass, carbon, stainless steel or many other
materials to increase wear resistance and strength, whatever your project or
build, we are sure to have a material that will work for you.
THE MAIN PROPERTIES OF PTFE
If you were trying to invent a highly flexible,
chemical resistant, thermal resistant, non-stick and electrically resistant
material, and it hadn’t already been done, you’d be hoping you could come up
with a material somewhere nearly as good as PTFE is in these areas.
PTFE’s melting point is around 327°C, and
pure PTFE is almost totally chemically inert, highly insoluble in most solvents
or chemicals, and thermally stable enough to be used between -200 degrees C and
+260 degrees C without degrading.
Other useful PTFE properties are its high
flexural strength, even in low temperatures, high electrical resistance and
dielectric strength, resistance to water (owing to fluorine’s high
electronegativity), and low coefficient of friction. PTFE’s density is also
very high, at 2200 kg/m3.
In fact, beyond reaction to some chemical
agents and solvents (for example, chlorine trifluoride, cobalt(III) fluoride,
xenon difluoride or elementary fluorine if at a high pressure and temperature),
the only factor to be taken into consideration when using PTFE is that it does
not have a good resistance to high energy radiation, which will cause breakdown
of the PTFE molecule.
MODIFIED PTFE PROPERTIES
In addition to pure PTFE, there are two
co-polymers which are equally as useful as PTFE, but with some different properties.
PFA or Perfluoroalkoxy has very similar
properties to PTFE in that it is very chemically resistant, flexible and
thermally stable (with continuous use up to 260 degrees C), but while PTFE does
have some tendency to creep, PFA is creep resistant and is excellent for
melt-processing, injection moulding, extrusion, compression moulding, blow
moulding, and transfer moulding.
TFM, known as PTFE-TFM, is
polytetrafluoroethylene with perfluoropropylvinylether as an additional
modifier, giving a denser material which is stiffer, also creep resistant like
PFA, and weldable.
FILLED PTFE
Pure or virgin PTFE can deform badly under
a load, but the use of fillers can help with this, though it should be noted
that not all filled PTFE is suitable for use with food.
Adding a filler to PTFE can increase its
strength, improve resistance to abrasion, add electrical conductivity and more;
however, adding fillers can also reduce some of the advantageous PTFE
properties, such as chemical resistance which will be limited by that of the
filler.
Fillers used can range from glass in
various percentages, stainless steel, molybdenum disulphide, carbon or
graphite, depending on which properties are to be improved.
ADVANTAGES AND BENEFITS OF USING PTFE
The biggest advantage of PTFE is its
versatility, and the range of applications over so many products and different
industries for this material is staggering.
The use of PTFE can have massive benefits
in manufacturing and engineering, not just in making tubes or liners for
handling or storing corrosive chemicals, but by coating parts such as bearings
or screws to increase the lifetime of both the parts themselves and the
machinery they are part of.
A PTFE-coated screw will be resistant to
corrosion, due to PTFE’s ability to repel water and oil, and lubricated by the
material to smoothly drive into whatever surface you are fastening to, with
reduced friction, resulting in less wear on both the screw and the surface, and
a longer-lasting, more secure finish.
Friction and wear can also be factors with
bearings, and a PTFE coat can give the same benefits as with coating screws,
with the additional advantage that the coating will also be heat-resistant.
It’s clear that longer lasting, higher-performance
parts can add to the efficiency of any machinery, reduce the need to constantly
acquire replacement parts, both saving money and the time needed to fit the
replacements, as well as reducing waste. This will also reduce maintenance needs
as there are less likely to be faults with the equipment, and also greatly
reduce, or even eliminate, any expensive manufacturing downtime due to faults
or repairs.
Cleaning of equipment can also be reduced
in some cases as a PTFE coat is non-wetting, facilitating self-cleaning of
parts.
And Teflon textile finishes can even help
the environment, because, when applied to fabric, the finish will repel water
and oil stains, reducing the need to use dry cleaning, and fabrics will also
dry more quickly, using less energy with tumble drying, and last longer due to
reduced wear.
With the added advantages that PTFE is
non-toxic, has only a minor contraindication for humans from polymer fume fever
(only if the temperature of any Teflon-coated pans reaches 260 degrees C) and
is FDA approved and food-safe, this material really is of great benefit in many
different areas.
INTERESTING USES OF PTFE
As well as coating everything from pans to
bearings, PTFE is also used to stop insects climbing walls as the material is so
‘non-stick’ that insects (and even geckos) are unable to grip.
The polymer is used frequently as a coating
on catheters to inhibit bacteria and infections and is also used as a graft
material in surgery.
You’ll have heard of Gore-Tex, and it’s
PTFE again, this time as a thin, porous membrane to make breathable rain wear,
or for medical implants, wiring insulation and sealants.
Bearing in mind that PTFE was discovered by
happy accident in 1938, it’s difficult to imagine our world today without it.
If you’re interested in using PTFE for any
of your projects, or if you’d like to find out more information about the
properties of PTFE, please do get in touch and we’d be happy to talk you
through your options.
Tags:PTFE,Polytetrafluoroethylene
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