PEEK vs ULTEM vs Polycarbonate: Which High-Temp Material?

If your part has to survive real heat, chemicals, or load, the material matters more than almost anything else. Pick too little and the part fails in service. Pick too much and you pay for performance you never needed. This guide walks through the four materials that cover most high-temperature work, so you can match the material to the job instead of guessing.

One thing up front: there is no single best material here. PEEK is not better than nylon, it is better for certain parts and wildly overkill for others. The right answer is always the cheapest material that clears your actual requirements, with a little margin. Let's find yours.

What counts as high-temp, and why does it matter?

Ordinary printing plastics like PLA start to soften around 50 to 60°C, which is barely above a hot car interior. That is fine for a display model and useless for a part near an engine, a motor, a steam line, or a sterilizer. A high-temp material is one that keeps its strength and shape well past that point, from roughly 110°C for polycarbonate up to 250°C and beyond for PEEK.

The catch is that the same property that makes these materials survive heat in service also makes them need heat to print. The higher the performance, the hotter the nozzle and chamber have to run, which is the real line between a hobby printer and an industrial one.

The four materials at a glance

Material	Heat resistance	Strength	Chemical resistance	Relative cost
PEEK	Highest (~250°C+)	Very high	Excellent, autoclavable	Highest
ULTEM (PEI)	High (~170 to 217°C)	High	Very good, flame retardant	High
Polycarbonate	Moderate (~110 to 140°C)	High impact	Moderate	Low to moderate
Nylon (PA)	Lower	Tough, wear-resistant	Good (oils, fuels)	Low

Treat these as planning ranges, not datasheet spec. Exact numbers vary by grade and by whether the material is filled with carbon fiber or glass. When a part is borderline, check the specific grade's datasheet or ask an engineer.

PEEK: when nothing less will do

PEEK is the top of the stack. It holds its strength continuously around 250°C, shrugs off aggressive chemicals, and is autoclavable, which is why it shows up in aerospace, medical, oil and gas, and semiconductor work. If your part sees sustained high heat, harsh solvents, or repeated sterilization, PEEK may be the only material on this list that clears the bar.

The tradeoffs are cost and difficulty. PEEK is the most expensive material here and the most demanding to print, needing very high and tightly controlled temperatures. The rule of thumb: reach for PEEK when your requirements genuinely need it, not by default. A lot of parts that get specified in PEEK would do fine in ULTEM for a fraction of the cost.

ULTEM: most of the performance, less of the cost

ULTEM (the brand name for PEI) is the practical workhorse of high-performance printing. It gives you a large share of PEEK's heat and chemical resistance at a meaningfully lower cost, and it is flame retardant with low smoke, which is exactly why it is so common in aircraft interiors and other spaces with fire-safety rules.

For most parts that need to perform above polycarbonate's range but do not demand PEEK's absolute top end, ULTEM is the sweet spot. If you find yourself unsure between PEEK and ULTEM, ULTEM is usually the right starting point, and you move up to PEEK only if testing shows you need to.

Polycarbonate: strength and clarity without the heat ceiling

Polycarbonate is where a lot of practical engineering parts actually belong. It is extremely impact resistant, can be made optically clear, holds up to roughly 110 to 140°C, and prints far more easily and cheaply than PEEK or ULTEM. For housings, guards, brackets, light covers, and durable functional parts that do not see extreme heat, PC is often the smart, affordable answer.

If your part's real requirement is "tough and does not crack," rather than "survives an oven," polycarbonate probably clears it without the high-performance price tag.

Nylon: tough, affordable, everyday functional

Nylon is the flexible, wear-resistant workhorse. It excels at gears, bushings, living hinges, cable guides, and functional parts that need to bend without breaking and resist abrasion over time. It also handles oils and fuels well, which makes it useful in automotive and shop settings.

Its limits are a lower temperature ceiling than the others and a thirst for moisture. Nylon absorbs water from the air, which hurts print quality, so it has to be dried and kept dry. Within its range, though, it is hard to beat on toughness per dollar.

So how do you actually choose?

Work from your hardest requirement down, and stop at the first material that clears it:

• Sustained high heat, harsh chemicals, or sterilization? Start at PEEK.
• High heat or flame-safety rules, but not PEEK's extreme end? ULTEM.
• Needs toughness and impact strength, moderate heat at most? Polycarbonate.
• Needs flexibility, wear resistance, and low cost? Nylon.

The most common and most expensive mistake is over-specifying. Teams reach for PEEK because it sounds like the safe choice, then pay many times over for heat resistance the part never sees. Spec the cheapest material that clears your real conditions with a sensible margin, and only move up if testing tells you to.

Do you need a special printer for these?

For PEEK and ULTEM, yes. They need very high nozzle temperatures and a heated chamber to print without warping or delaminating, and most desktop machines simply cannot get there. Polycarbonate and nylon are more forgiving but still ask for more capability than an entry-level printer.

This is the whole reason industrial high-temp printers exist. The 22 IDEX v4 runs dual extruders rated to 500°C, which covers this entire material list, and it is open material, so you are not locked into one supplier's filament and can run the exact grade your part needs. That flexibility matters here, because the right material is the point of this whole guide.