PTFE: Polytetrafluoroethylene

General Properties

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PTFE

Polytetrafluoroethylene


Polytetrafluoroethylene (PTFE) is the most widespread and important fluoropolymer. It is a linear, semi-crystalline thermoplastic showing several transitions between 0°C and 340°C. Due to its abrasion resistance and high chemical resistance, PTFE is used often in tribological systems. PTFE is also used as a coating in frying pans in many households.

Structural Formula


Properties

Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.Glass Transition Temperature120 to 130°C
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Temperature325 to 335°C
Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).Melting Enthalpy82 J/g
Decomposition Temperature575 to 590°C
Young's Modulus400 to 750 MPa
Coefficient of Linear Thermal Expansion (CLTE/CTE)The coefficient of linear thermal expansion (CLTE) describes the length change of a material as a function of the temperature.Coefficient of Linear Thermal Expansion100 to 150 *10-6/K
Specific Heat Capacity1.0 J/(g*K)
Thermal ConductivityThermal conductivity (λ with the unit W/(m•K)) describes the transport of energy – in the form of heat – through a body of mass as the result of a temperature gradient (see fig. 1). According to the second law of thermodynamics, heat always flows in the direction of the lower temperature.Thermal Conductivity0.23 to 0.25 W/(m*K)
DensityThe mass density is defined as the ratio between mass and volume. Density2.13 to 2.23 g/cm³
MorphologySemi-crystalline thermoplastic
General propertiesGood thermal and oxidative stability. High toughness. Very good chemical resistance. Good electrical insulation. Low friction coefficient. High UV resistance
ProcessingSpecial techniques for extrusion, compression/SinteringSintering is a production process for forming a mechanically strong body out of a ceramic or metallic powder. sintering for molding, films, components
ApplicationsChemical plant construction. Food and pharma technology. Medical engineering. Nonstick coating. Sealing technology. High-frequency technology

NETZSCH Measurement

InstrumentDSC 204 F1 Phoenix®
Sample Mass12.80 mg
IsothermalTests at controlled and constant temperature are called isothermal.Isothermal Phase20 min
Heating/Colling Rates10 K/min
CrucibleAl, pierced lid
AtmosphereN2 (40 ml/min)

Evaluation

The DSC curve of the PTFE sample exhibits two overlapping peaks around 20°C. The peaks were sharper in the 2nd heating (red) than they were in the 1st heating (blue) with peak temperatures of 23°C and 32°C. A very weak Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition at approx. 130°C was detected in the 2nd heating. The melting transitions peaked at 334°C in both heatings. The melting enthalpy with 65 J/g in the 2nd heating (red) is approx. 11% below the melting enthalpy in the 1st heating. This indicates a lower Crystallinity / Degree of CrystallinityCrystallinity refers to the degree of structural order of a solid. In a crystal, the arrangement of atoms or molecules is consistent and repetitive. Many materials such as glass ceramics and some polymers can be prepared in such a way as to produce a mixture of crystalline and amorphous regions.crystallinity in the 2nd heating and is consistent with the somewhat clearer Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition step, which indicates an increase in amorphous content.