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.