PTFE (Polytetrafluoroethylene) is among the most chemically inert materials available for industrial use. Its carbon-fluorine bond structure makes it resistant to attack by virtually all chemicals — a property that makes PTFE gaskets and seals the default choice for corrosive chemical processing applications worldwide.
This guide provides a practical chemical resistance reference for PTFE and expanded PTFE (ePTFE) seals. Use it to verify compatibility before specifying PTFE for your next project.
How PTFE Chemical Resistance Works
PTFE's chemical inertness comes from its unique molecular structure. The carbon chain is completely surrounded by fluorine atoms — the strongest single bond in organic chemistry (C-F bond energy: ~485 kJ/mol). This "fluorine shield" prevents chemical attack because:
- Fluorine is the most electronegative element — it strongly withdraws electron density from the carbon backbone, making it unreactive
- The carbon-fluoroine bonds are too strong for most chemicals to break at operating temperatures
- PTFE has no double bonds, double bonds, or other reactive functional groups
Chemical Resistance Quick Reference
Acids
| Chemical | PTFE Rating | Notes |
|---|---|---|
| Hydrochloric Acid (all concentrations) | Excellent | Any temp, any concentration |
| Sulfuric Acid (up to 98%) | Excellent | Room temp. May discolor at >150°C |
| Nitric Acid (up to 70%) | Excellent | Any concentration at room temp |
| Phosphoric Acid (all concentrations) | Excellent | Any temp |
| Hydrofluoric Acid (all concentrations) | Excellent | Unique — most materials fail here |
| Acetic Acid (glacial) | Excellent | Any temp |
| Chromic Acid | Excellent | Room temp only |
Alkalis & Bases
| Chemical | PTFE Rating | Notes |
|---|---|---|
| Sodium Hydroxide (Caustic Soda) | Excellent | Any concentration and temp |
| Potassium Hydroxide | Excellent | Any concentration and temp |
| Ammonium Hydroxide | Excellent | Any concentration |
| Calcium Hydroxide | Excellent | Any concentration |
Solvents
| Chemical | PTFE Rating | Notes |
|---|---|---|
| Acetone | Excellent | Any temp |
| Methanol / Ethanol | Excellent | Any concentration, any temp |
| Toluene / Xylene | Excellent | Any temp |
| MEK (Methyl Ethyl Ketone) | Excellent | Any temp |
| Isopropyl Alcohol | Excellent | Any temp |
| Ethyl Acetate | Excellent | Any temp |
| Chloroform / Methylene Chloride | Excellent | Any temp |
| Perchloroethylene | Excellent | Any temp |
Hydrocarbons & Fuels
| Chemical | PTFE Rating | Notes |
|---|---|---|
| Gasoline / Petrol | Excellent | Any temp |
| Diesel Fuel | Excellent | Any temp |
| Jet Fuel (JP-4, JP-5, JP-8) | Excellent | Any temp |
| Biodiesel (B100) | Excellent | Any temp |
| Natural Gas | Excellent | Any temp |
| LPG (Propane/Butane) | Excellent | Any temp |
| Mineral Oils | Excellent | Any temp |
| Cutting Fluids | Excellent | Any temp |
Other Industrial Chemicals
| Chemical | PTFE Rating | Notes |
|---|---|---|
| Chlorine (dry gas) | Excellent | Any temp |
| Chlorine Water | Excellent | Room temp |
| Bromine (liquid) | Excellent | Room temp. Hot bromine: test required |
| Hydrogen Peroxide (90%) | Excellent | Up to 60°C |
| lodine | Excellent | Room temp |
| Phenol | Excellent | Any temp |
| Formaldehyde | Excellent | Any temp |
| Sea Water | Excellent | Any temp |
| Steam (saturated) | Excellent | Up to 260°C |
| Brine Solutions | Excellent | Any temp |
Chemicals That Attack PTFE
PTFE is attacked by only a very small number of chemicals:
| Chemical | PTFE Rating | Alternative Materials |
|---|---|---|
| Molten Alkali Metals (Na, K, Li) | Not Compatible | Graphite, glass-filled PTFE |
| Elemental Fluorine (F2) >200°C | Not Compatible | Kel-F, Halar |
| Lewis Salts (AlCl3, FeCl3) at high temp | Caution | Graphite gaskets |
| Atomic Oxygen (high temp plasma) | Not Compatible | Ceramic coatings |
Important Notes
Temperature Effects
While PTFE is chemically resistant across its full temperature range (-260°C to +260°C), certain chemical combinations at elevated temperatures require caution. For example:
- Fluorine and chlorine gases at temperatures above 200°C can penetrate PTFE
- Concentrated sulfuric acid at temperatures above 150°C may cause surface discoloration (though seal integrity is usually maintained)
- Halogenated solvents at reflux temperature may cause slight swelling in some cases
Fillers and Additives
Filled PTFE compounds (glass-filled, carbon-filled, graphite-filled) may have different chemical resistance than pure virgin PTFE. Glass-filled PTFE, for example, may be attacked by strong alkalis. Always specify your chemical environment when ordering filled compounds.
How to Use This Guide
This guide covers the most common industrial chemicals. For specialty chemicals, rare compounds, or mixtures, we recommend:
- Checking published chemical resistance data from your chemical supplier
- Requesting a material compatibility consultation with our engineering team
- For critical applications, conducting small-scale immersion testing before full deployment
Need Help with Your Application?
If you're specifying PTFE seals for a specific chemical environment, contact our engineering team with your chemical, temperature, and pressure requirements — we'll help you select the right grade.
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