PTFE as a Sealing Material — Properties, Advantages and Limitations

PTFE (polytetrafluoroethylene, commercially known as Teflon) is the world's most widely used sealing material in demanding industrial applications. Its unique combination of chemical resistance, broad temperature range and extremely low friction makes it indispensable in many sealing applications.

Why PTFE for Seals?

PTFE resists virtually all industrial chemicals. It does not react with acids, bases, solvents or hydrocarbons. Only molten alkali metals and fluorine gas under extreme conditions can damage it. This universal chemical resistance makes PTFE a safe choice when a seal's chemical exposure is varied or unknown.

Temperature Range

PTFE operates continuously from –200 °C to +260 °C. This is the widest service temperature range of any sealing material. From cryogenic applications to superheated steam lines — PTFE performs.

For comparison: rubber seals typically operate from –40 to +150 °C and POM seals from –40 to +100 °C.

Friction and Non-Stick Properties

PTFE has the lowest coefficient of friction of any solid material — approximately 0.04–0.10. This means PTFE seals slide on shafts with near-zero friction, reducing energy loss and wear. Shaft seals and piston seals benefit from this especially.

PTFE also does not stick to mating surfaces, which simplifies maintenance and replacement work.

Challenges of PTFE in Seals

Pure PTFE is a soft material and creeps under load (cold flow). This means that when compressed, a PTFE seal slowly deforms over time, which can cause seal leakage. There are two solutions to this problem:

1. Filled PTFE grades: Glass fiber, carbon, graphite or bronze significantly improve PTFE's stiffness and creep resistance. For example, 25% glass-fiber-filled PTFE withstands loading considerably better than virgin PTFE.

2. Spring-energized seals: A metal spring keeps the PTFE seal under constant compression, automatically compensating for creep and thermal expansion.

PTFE Seal Types

Type	Application	Advantages
O-rings	Static sealing	Chemical resistance, wide temperature range
Shaft seals	Rotating shafts	Low friction, no lubrication required
Piston seals	Hydraulic cylinders	Low friction, stick-slip-free motion
Flange gaskets	Pipe connections	Universal chemical resistance
V-rings	High pressure	Spring-energized, automatic compensation
Mechanical face seals	Pumps, mixers	Long service life, dry running capability

Filled PTFE Grades Comparison

Filler	Improves	Typical Application
Glass fiber (15–25%)	Stiffness, creep resistance	General-purpose seals, flange gaskets
Carbon/graphite	Wear resistance, thermal conductivity	Shaft seals, slide bearings
Bronze	Compressive strength, thermal conductivity	Hydraulic seals, heavy-duty loading
Stainless steel	Hardness, wear resistance	Abrasive environments
MoS2	Friction (even lower)	Applications requiring dry lubrication

Application Areas

Chemical industry: Pipe flange gaskets, valve seats, reactor seals — everywhere aggressive chemicals place demands on sealing materials.

Food and pharmaceutical industry: FDA-approved, odorless and tasteless PTFE is suitable for direct food and drug contact. Easy to clean and withstands sterilization.

Hydraulics and pneumatics: Piston and rod seals where PTFE's low friction enables precise, smooth motion without stick-slip effects.

Oil and gas industry: High-pressure valve seals, compressor piston rings and corrosion-resistant flange gaskets.

Summary

PTFE is the superior sealing material when an application demands chemical resistance, a wide temperature range or low friction. Fillers solve pure PTFE's biggest weakness — creep — and further extend its range of use. Selecting the right PTFE grade depends on the application's pressure, temperature, chemical environment and type of motion.

Need PTFE stock shapes for seal manufacturing?

We supply virgin and filled PTFE as rods, tubes and sheets. Tell us about your application — we'll help select the right grade.