Polytetrafluoroethylene (PTFE) is a tetrafluoroethylene polymer featuring a unique combination of physical-chemical features that make it different from any other plastic material. The main features of PTFE are:
- extreme chemical inertness
- excellent heat resistance
- optimum dielectric properties
- zero hygroscopicity and maximum resistance against solvents
- optimum resistance to ageing
- self-lubricating properties and minimum friction coefficient.
PTFE withstands virtually all chemical reactants. It is only attacked by elemental alkali metals, chlorotrifluorides and elemental fluorine at high pressure and high temperature. PTFE is indifferent to all solvents up to 260°C. It can only be swelled and melt by some highly fluorinated oils at temperatures around the crystalline melting point.
PTFE has a low heat transmission factor and can be therefore considered a thermoinsulating material. It also shows flame-retardant properties and is stable at 260°C for an indefinite length of time.
PTFE has optimum dielectric properties within a vast range of temperatures and frequencies. As water absorption is virtually inexistent, these properties are maintained even after a prolonged exposure to weather agents. Electric strength is practically not influenced by the operating temperature. The resistance to arcing of PTFE is considerable and the spark does not generate carbon residues but only non-conductive vapours. The other electric properties (dielectric constant, surface resistivity, volume resistivity, power factor, etc.) show very interesting values.
The following table displays the mechanical properties of PTFE, measured at the temperature of 23°C. Take note that between 19°C and 21°C, the material shows a transition point determined by a modification of its crystalline structure which provokes a loss of volume of about 1%. Other particular properties of PTFE are its non-adhesivity and its low friction coefficient, above all under high loads.
VIRGIN P.T.F.E (POLİTETRAFLOROETİLEN ) COMPARATIVE TECHNICAL VALUES TABLE
|PROPERTIES||TEST METHOD||UNIT||PURE PTFE|
|SPECIFIC GRAVITY||ASTM D 1457/18||gr/cm³||2,14-2,2|
|MELTING TEMPERATURE||ISO 3146||°C||325-330|
|PULLING STRENGTH||ASTM D- 1708||kg/cm²||250-300|
|ELONGATION UPON BREAKING||ASTM D- 1708||%||250-300|
|RESISTANCE TO STROKE||ASTM D- 256||cm.kg/cm||15,5|
|SHORE D HARD||ASTM D- 2240||–||53-57|
|DEFORMITY UNDER LOAD|
230°C, 1day, 140kg/cm²
|ASTM D- 621||%||9,5-11|
|D-ELECTRIC RESISTANCE||ASTM D- 149||KV/mm||50-80|
|THERMAL CONDUCTIVITY||ASTM C- 177||Kcal/cm.°C.hour||0,035|
|THERMAL EXPANSION||ASTM E 831||10-5/°C||12-14|
|INFLAMMABILITY TEMPERATURE||ASTM D- 1929||°C||530|
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