7/27/2019 General Temperature Range

1/2

GENERAL TEMPERATURE RANGE: -300 to +500 FPolytetrafluoroethylene (PTFE) is a completely fluorinatedpolymerproduced when the

monomertetrafluoroethylene (TFE) undergoes free radical vinylpolymerization. As a

monomer, TFE is made up of a pair ofdouble-bondedcarbonatoms, both of which have two

fluorine atomscovalently bondedto them. Thus the name: tetra means there are fouratomsbondedto the carbons, fluoro means those bonded atoms are fluorine, and

ethylene means the carbons are joined by a double bond as in the classic ethylenestructure. (Ethylene has hydrogen atoms attached to the carbons, as in Figure 50, but TFEhas fluorine in place of the hydrogen, as in Figure 51.) When TFE polymerizes into PTFE,

the carbon-to-carbon double bond becomes a single bond and a long chain of carbon atomsis formed, as in Figure 52. This chain is the polymers backbone.With a ratio of four fluorine atoms to every two carbon atoms, the backbone is essentiallyshielded from contact. Its almost impossible for any other chemical to gain access to the

carbon atoms. Even if an agent could gain access, the carbon-to-fluorine bonds have highbond disassociation energy, so theyre almost unbreakable. This makes PTFE the most

chemically resistantthermoplasticpolymer available. PTFE isinertto almost all chemicalsandsolvents, allowing PTFE parts to function well in acids,alcohols, alkalis, esters, ketones,

andhydrocarbons. There are only a few substances harmful to PTFE, notably fluorine,chlorine trifluoride, and molten alkali metal solutions at high pressures.PTFE is also very slippery. By its very nature, the fluorine in PTFE repels everything. As partof amolecule, fluorine is decidedly anti-social. Anything getting close is repelled, andrepelled molecules cant stick to the PTFE surface. This makes PTFE perfect for applications

requiring a low coefficient of friction. The only thing slicker than PTFE is ice! Because they

are essentially self-lubricating, PTFE parts are ideal for applications in which externallubricants (such as oils and greases) cant be used.PTFE can withstand a wide range of temperatures (-300 to 500 F, -184 to 260 C).Because its non-flammable and doesnt dissipate heat, PTFE is often used as a thermal

insulator (as in welding equipment). At the other extreme, PTFE is widely used in very cold

environments (such as space). Other important properties include resistance to bothweatheringandwaterabsorption. PTFE can also act as an electrical insulator.Because of its chemical inertness, PTFE cannot be cross-linked like anelastomer. Thereforeit has nomemoryand is subject tocreep(also known ascold flow). Creep is the increasing

deformationof a material under a constant compressiveload. This can be both good and

bad. A little bit of creep allows PTFE seals to conform tomating surfacesbetter than mostother plastic seals. Too much creep, however, and the seal is compromised. Compounding

fillersare used to control unwanted creep, as well as to improve wear,friction, and otherproperties.Keep in mind that PTFE fillers dont act like elastomer fillers, which become chemicallybonded to the elastomer. With polytetrafluoroethylene, the highshear modulusfillers areencapsulatedand bound by the low shear modulus PTFE. Because it does not possess a

good elastic memory at or below normal temperatures, PTFE may need to be heated to

facilitate installation. PTFE has poor cut resistance, so extra care must be taken not todamage seals during installation.

http://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#monomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#monomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerizehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerizehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerizehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#doublebondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#doublebondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#doublebondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#atomhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#atomhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#atomhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#covalentbondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#covalentbondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#covalentbondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#bondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#bondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#bondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#thermoplastichttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#thermoplastichttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#thermoplastichttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#inerthttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#inerthttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#inerthttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#solventhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#solventhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#solventhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#alcoholshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#alcoholshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#alcoholshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#hydrocarbonshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#hydrocarbonshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#hydrocarbonshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moleculehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moleculehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moleculehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#weatheringhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#weatheringhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moistureresistancehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moistureresistancehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#absorptionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#absorptionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#absorptionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#elastomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#elastomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#elastomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#memoryhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#memoryhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#memoryhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#creephttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#creephttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#creephttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#coldflowhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#coldflowhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#coldflowhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#deflectionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#deflectionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#loadhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#loadhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#loadhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#matingsurfaceshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#matingsurfaceshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#matingsurfaceshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#fillerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#fillerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#frictionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#frictionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#frictionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#shearmodulushttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#shearmodulushttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#shearmodulushttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#encapsulationhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#encapsulationhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#encapsulationhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#shearmodulushttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#frictionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#fillerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#matingsurfaceshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#loadhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#deflectionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#coldflowhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#creephttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#memoryhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#elastomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#absorptionhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moistureresistancehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#weatheringhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#moleculehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#hydrocarbonshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#alcoholshttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#solventhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#inerthttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#thermoplastichttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#bondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#covalentbondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#atomhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#doublebondhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymerizehttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#monomerhttp://www.rlhudson.com/O-Ring%20Book/glossary-gloss.html#polymer

7/27/2019 General Temperature Range

2/2