The short answer
For continuous heat, the usual ladder is PBT and nylon 66 (to about 120–150°C), PPA (to about 140–170°C), sulfones and PEI (to about 150–180°C), PPS (to about 200–220°C) and PEEK (to about 240–260°C). Pick the lowest step that holds your part's load at its real temperature.
"High-temperature plastic" can mean surviving a brief heat spike, or running hot for years. Those are different questions, and the data sheet numbers that answer them are different too.
Common resins by heat resistance
| Resin | Approx. continuous use | Heat deflection, 1.8 MPa | Notes |
|---|---|---|---|
| ABS | ~60–80°C | ~85–100°C (unfilled) | Low-heat housings |
| Polycarbonate | ~115–125°C | ~125–140°C | Clear, tough, amorphous |
| PBT (glass-filled) | ~120–140°C | ~200–210°C | Electrical, low moisture |
| Nylon 66 (heat-stabilized, glass-filled) | ~120–150°C | ~245–255°C | Under-hood workhorse |
| PPA (glass-filled) | ~140–170°C | ~270–290°C | Hot, wet service |
| Polysulfone / PPSU | ~150–180°C | ~175–210°C | Clear or amber, steam sterilizable |
| PEI | ~170–180°C | ~200–215°C | Amber, flame resistant, strong |
| PPS (glass-filled) | ~200–220°C | ~260°C+ | Chemical resistant, low cost for its heat |
| PEEK | ~240–260°C | ~315°C (glass-filled) | Top of the range, high cost |
| PFA / PTFE | ~260°C | Low (soft under load) | Chemical and electrical; low strength |
Approximate values for typical grades. Continuous use limits depend on the property, load, thickness and environment; for electrical and safety parts, check the UL relative thermal index (RTI) of the specific grade.
Which heat number to use
- Heat deflection temperature (HDT): a short-term test under load. Useful for comparing stiffness when hot, not for long-term life.
- Continuous use temperature or RTI: how hot a grade can run for years. Use this for parts that stay hot.
- Glass transition (Tg): where amorphous resins soften quickly. Keep amorphous parts well below it.
- Melting point (Tm): the hard upper limit for semi-crystalline resins; glass-filled grades can carry load until close to it.
How to choose
- Define the heat: peak and continuous temperatures, and for how long.
- Add the load at that temperature; creep is often what fails first.
- List the environment: oils, coolant, steam, hot water, UV.
- Note special needs: flame rating, clarity, food contact, electrical properties.
- Pick the lowest-cost resin that passes, then test parts at temperature.
See also parts softening under heat, PEEK alternatives, PPA vs. nylon 66 and PEEK vs. PEI.
Grades we source
We source high-temperature resins including PPA, PPS, PEI, sulfones, PEEK and fluoropolymers, from small quantities up, with a COA on every lot, tested to ASTM or ISO methods. See PPS, PEI and PEEK.
Common questions
What plastic handles the highest temperature?
Among common high-performance resins, PEEK and the fluoropolymers PTFE and PFA have the highest continuous use temperatures, around 240–260°C. PTFE is not melt-processable; PFA and PEEK can be injection molded. Polyimides go higher but are not processed like standard thermoplastics.
What is the difference between heat deflection temperature and continuous use temperature?
Heat deflection temperature (HDT) is a short-term test: the temperature at which a bar bends a set amount under load. Continuous use temperature is how hot a part can run for years without losing too much strength. Continuous use is usually far lower than HDT.
Does glass fiber raise heat resistance?
It raises HDT a lot in semi-crystalline resins such as nylon, PBT, PPS and PEEK, because the fibers carry load up to near the melting point. In amorphous resins such as PC or PEI the gain is small. Glass does not change long-term heat aging much.
What is a cheaper alternative to PEEK for high heat?
PPS is the usual first choice for parts that run up to about 200–220°C, at a fraction of PEEK's cost. PPA, PEI and sulfones cover other combinations of heat, toughness and clarity.
What is the UL relative thermal index (RTI)?
A UL rating of the temperature at which a specific grade keeps half of a property after long-term aging. It is grade- and thickness-specific, and it is the number to check for electrical and safety-related parts.
Tell us the part and its temperature
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province