PTFE Material Properties

PTFE Material Properties: specs, selection tips and practical notes for PTFE parts and powder presses. Published by HEMSUN, Gujarat, India.

Quick Answer

PTFE (polytetrafluoroethylene) has a specific gravity of 2.14–2.20 g/cm³, a continuous service range of approximately -200°C to +260°C, a coefficient of friction of 0.04–0.10 — the lowest of any solid material — and resists effectively every industrial chemical. Its limitations are entirely mechanical: low compressive strength, significant cold flow under sustained load, high thermal expansion, and poor abrasion resistance.

Physical Properties

Property	Typical value (virgin PTFE)	What it means in service
Specific gravity	2.14–2.20 g/cm³	Solid PTFE sinks in water. Density below this range indicates voids.
Water absorption	~300°C	Degrades and releases hazardous products. Never exceed.
Flammability	UL94 V-0	Does not support combustion.

Electrical Properties

Property	Typical value	Practical consequence
Dielectric strength	Very high	Excellent insulator, used in high-frequency applications.
Volume resistivity	> 10¹⁸ Ω·cm	Effectively non-conductive.
Dissipation factor	Extremely low	Minimal signal loss; stable across frequency.
Magnetic response	None	Non-magnetic — suits sensitive instrumentation and test rigs.

Note: carbon-filled and bronze-filled PTFE are electrically conductive. If insulation matters, specify virgin explicitly.

Chemical Resistance

PTFE’s chemical resistance comes from the carbon-fluorine bond, one of the strongest single bonds in organic chemistry, which shields the carbon backbone from attack. In practical terms PTFE is unaffected by:

All mineral acids including sulphuric, hydrochloric, nitric, hydrofluoric and phosphoric, at all concentrations
All alkalis including concentrated caustic soda and potash
Organic solvents including chlorinated, aromatic and ketone solvents
Halogens, oxidising agents, peroxides and bleaches
Hydrocarbons, fuels, oils and refrigerants
Steam and hot water

The known exceptions are narrow: molten alkali metals (sodium, potassium), elemental fluorine at elevated temperature and pressure, and certain fluorinating agents such as chlorine trifluoride. In normal industrial service you will exhaust PTFE’s mechanical capability long before its chemical capability.

Where PTFE Actually Fails

Because the chemical resistance is so complete, buyers sometimes specify PTFE and then are surprised when it fails. It does fail — mechanically. The four modes, in order of frequency:

Cold flow at the seat. Sustained seat load flattens the contact area until the ball stops sealing. The most common failure by a wide margin. Filled grades substantially delay it.
Abrasive wear. Particulate in the media erodes the soft surface. UHMWPE or a filled PTFE grade usually outlasts virgin here.
Thermal overrun. Sustained operation above 260°C degrades the polymer. There is no grade that fixes this — you need a different material.
Internal voids. Not a material limitation but a manufacturing one: incomplete compaction or a wrong sintering ramp leaves cavities that fail under pressure. Density testing screens for it.

Diagnosing which one you have is usually straightforward from the worn part — a flattened contact area means cold flow, uniform surface erosion means abrasion, discolouration and embrittlement means thermal damage.

What Is a PTFE Ball? (/what-is-a-ptfe-ball)
Filled PTFE Balls (/filled-ptfe-ball) — improving the mechanical numbers
Common Failure Modes (/common-failure-modes)
Grades & Tolerances (/ptfe-ball-grades-and-tolerances)
PTFE Ball Glossary (/ptfe-ball-glossary)

Frequently Asked Questions

What is the density of PTFE?

Virgin PTFE has a specific gravity of 2.14 to 2.20 g/cm³. This is a useful quality check: a finished ball measurably below that range usually indicates internal voids or incomplete sintering, which is why density verification is part of our inspection routine.

What is the maximum temperature for PTFE?

Approximately +260°C for continuous service, with short excursions higher. Above roughly 300°C the polymer begins to degrade and can release hazardous decomposition products, so it should never be run there. At the other end, PTFE remains serviceable down to about -200°C, which is why it is used in cryogenic and LNG applications.

What is PTFE’s coefficient of friction?

Between 0.04 and 0.10 depending on load and counterface — the lowest of any bulk solid material. Unusually, PTFE’s static and dynamic friction are nearly equal, which means it does not stick-slip. That is why it moves smoothly at very low velocities where other polymers judder.

What chemicals attack PTFE?

Very few. PTFE resists effectively all acids, bases, solvents and oxidisers across its temperature range. The known exceptions are molten alkali metals, elemental fluorine at elevated temperature and pressure, and certain halogenated compounds under extreme conditions. In normal industrial service you are far more likely to run out of mechanical capability than chemical capability.

What is cold flow in PTFE?

Cold flow, or creep, is PTFE’s tendency to deform permanently under sustained mechanical load even at ambient temperature. It is the single most important practical limitation for check balls: a ball held against a seat under pressure gradually develops a flat at the contact point and stops sealing. Filled grades reduce it substantially; no grade eliminates it.

Is PTFE electrically insulating?

Yes. Virgin PTFE has a very high dielectric strength and extremely low dissipation factor, and is used as a high-frequency insulator. Note that carbon-filled and bronze-filled grades are electrically conductive, so if insulation matters you must specify virgin explicitly.

Does PTFE absorb water?

Essentially no — water absorption is under 0.01%. That means PTFE balls do not swell, do not change dimension with humidity, and can be stored indefinitely without conditioning, unlike nylon which absorbs moisture and grows measurably.