PTFE vs Graphite: Choosing a Sealing Material

Two workhorses, two different regimes

PTFE (polytetrafluoroethylene) and flexible graphite are the two most common sealing materials, but they solve different problems.

PTFE

Chemical resistance: inert to almost all chemicals except molten alkali metals and fluorine at high temperature.
Friction: very low, kind to shafts; ideal for food, pharma and pure-water duty.
Limit: creeps under load and softens above ≈ 260°C.

Flexible graphite

Temperature: stable to ≈ 450°C in non-oxidizing service, far above PTFE.
Pressure: no creep, excellent for high-pressure flanges and steam.
Limit: not suitable for strong oxidizers; softer on abrasive shafts.

Quick decision table

If you need…	Choose
Broad chemical resistance, low friction, food/pharma	PTFE packing or gasket
High temperature steam / thermal cycling	Graphite packing or sheet
Both, with some abrasion	Graphite-filled PTFE (balanced)

For a mixed duty, graphite-filled PTFE yarn combines chemical resistance with better high-temperature behavior than pure PTFE.

Frequently Asked Questions

Which lasts longer in high-temperature valve service?

Flexible graphite outperforms PTFE above roughly 260 °C. PTFE softens and cold-flows as temperature climbs, so for steam and high-heat valves graphite packing is the safer long-term choice.

Is PTFE or graphite better for chemical resistance?

PTFE has broader chemical inertness across acids, caustics and most solvents. Graphite is excellent for the vast majority of media but can oxidize in strong oxidizers such as concentrated nitric acid or fuming sulfuric acid, where PTFE is preferred.

Which is easier to install and seals at lower torque?

PTFE packs are softer and seat at lower gland torque, which is gentler on shafts and easier for field crews. Graphite needs higher gland stress to control leakage but holds a more stable seal under fluctuating pressure.

Can PTFE and graphite be used together?

Yes. Many modern braided packings combine a PTFE or graphite core with a graphite or PTFE yarn jacket to balance low friction with high-temperature stability — a common choice for pumps and mixers.