PTFE Properties: Density, Temperature Range and Strength

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Reviewed by MLC Editorial Team | 2 October 2026

PTFE (polytetrafluoroethylene) is a fluoropolymer used for seals, gaskets, bearings, linings and insulation where low friction, chemical resistance or a wide temperature range is needed. Unfilled PTFE has a density of 2.13 to 2.19 g/cm3, a maximum continuous service temperature of 260 C and a dynamic friction coefficient against steel of 0.06 to 0.08. It is a soft material: its tensile strength of 15 to 35 MPa is a small fraction of any engineering metal.

Properties of unfilled PTFE

Values are for virgin, unfilled PTFE at room temperature unless stated. Where the published datasheets agree, the table gives the agreed figure or the band they overlap on. Where they do not, it gives the spread of what is published and says so.

Property	Unfilled PTFE	Agreement
Density	2.13 to 2.19 g/cm3	Sources agree
Tensile strength	15 to 35 MPa	Sources agree
Elongation at break	150 to 350 %	Sources agree
Hardness	55 to 64 Shore D	Sources agree
Coefficient of friction, dynamic against steel	0.06 to 0.08	Sources agree
Maximum continuous service temperature	260 C	Sources agree
Minimum service temperature	-260 to -200 C	Published figures vary (2 sources)
Melting point	327 C	Sources agree
Thermal expansion, about 23 to 100 C	130 x 10-6 per K	Sources agree
Thermal conductivity	0.2 to 0.34 W/m.K	Published figures vary (5 sources)
Dielectric strength, thin film in air	60 to 80 kV/mm	Sources agree
Dielectric constant	2.1	Sources agree
Water absorption, 24 hours	0 to 0.05 %	Published figures vary (4 sources)

What the numbers mean in practice

The temperature range is the main reason PTFE is chosen. It keeps its properties from cryogenic temperatures up to 260 C and does not melt until 327 C. Published minimum temperatures differ, -260 to -200 C depending on the source, because the lower limit is set by how brittle the part is allowed to become, not by a change in the polymer.

The friction coefficient is among the lowest of any solid, which is why PTFE is used for dry bearings, slide pads and seal faces. The trade-off is strength and creep. PTFE deforms slowly under a steady load, so a PTFE gasket or seat relaxes after tightening and may need retorquing, and a PTFE bearing has to be sized for a low contact pressure.

Thermal expansion is high, 130 x 10-6 per K, many times that of steel. A PTFE part that fits at room temperature will be tight or loose at working temperature, so clearances have to allow for it.

PTFE is an electrical insulator with a low dielectric constant of 2.1, which stays almost constant across frequency. That, with near zero water absorption, is why it is used for cable insulation and high frequency components.

Filled PTFE

Glass, carbon, bronze and graphite fillers are added to reduce creep and wear and to raise stiffness. Filled grades have different values from the table above, in some cases very different, so use the supplier's datasheet for the specific compound. This page covers unfilled material only.

PTFE for seals and O-rings

Solid PTFE has almost no elastic recovery, so it does not behave like a rubber O-ring. It is used as back-up rings, as spring-energised or encapsulated seals, and as gaskets and valve seats. Where a chemically resistant seal has to be elastic, a perfluoroelastomer is the usual answer: see Kalrez and Chemraz FFKM O-rings and O-ring material selection.

References

BS EN ISO 13000 - Plastics, PTFE semi-finished products
ASTM D4894 - PTFE granular moulding and ram extrusion materials

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Frequently Asked Questions

What temperature can PTFE withstand?

Unfilled PTFE has a maximum continuous service temperature of 260 C and melts at 327 C. Published minimum service temperatures range from -260 to -200 C.

What is the density of PTFE?

Unfilled PTFE has a density of 2.13 to 2.19 g/cm3.

What is the coefficient of friction of PTFE?

The dynamic coefficient of friction of unfilled PTFE against steel is 0.06 to 0.08, among the lowest of any solid material.

Is PTFE the same as Teflon?

Teflon is a brand name for PTFE and related fluoropolymers. PTFE is the material itself, polytetrafluoroethylene, and is made by several manufacturers.

Independent UK engineering trade publication. Company profiles cross-referenced with Companies House.

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