Chemical resistance is one of the most common reasons to specify an engineering plastic over metal — and one of the easiest things to get wrong. “Chemical resistant” is never absolute: it depends on the chemical, the concentration, the temperature and the exposure time. Here is a practical framework.
The four variables that decide everything
- Chemical — acids, bases, solvents and oxidisers behave very differently.
- Concentration — a dilute acid and a concentrated one are different problems.
- Temperature — resistance drops sharply as temperature rises.
- Exposure time — continuous immersion is far harsher than occasional splash.
General starting points
| Material | Strengths | Watch out for |
|---|---|---|
| PTFE | Nearly all chemicals, high temperature | Molten alkali metals, some fluorinating agents |
| PP | Acids, bases, many solvents | Strong oxidisers, some hydrocarbons at high temp |
| HDPE | Acids, bases, alcohols | Hydrocarbons, strong oxidisers |
| UHMWPE | Similar to HDPE plus wear | Strong oxidisers; limited temperature |
| POM | Fuels, solvents, weak acids | Strong acids, strong bases |
| Nylon | Many solvents and oils | Strong acids, phenols; moisture |
How to use a chemical resistance chart
Charts are a starting point, not a guarantee. They usually assume a specific temperature and test duration. Always check the conditions behind the rating, and for critical applications run an immersion test with the actual media before committing to production.
A note on temperature
A material rated “resistant” at room temperature can fail quickly at 60 °C in the same chemical. If your process runs warm, treat the rating as a question, not an answer — and tell us the operating temperature when you enquire.
Need a part that survives a specific chemical?
Send us the chemical, concentration, temperature and exposure conditions and we will recommend the right material and supply your part. Request a quote.