Ultra-high-temperature polymers (PEEK, PEI/ULTEM, PEKK)

Published · Researched 2026-09-20

Overview — what it is, best uses, key context

The ceiling of FDM. PEEK (polyetheretherketone), PEI (polyetherimide, sold as ULTEM), and PEKK (polyetherketoneketone) are the three thermoplastics that survive continuous service above ~170 °C, and they do it with aerospace-grade chemical resistance, inherent flame retardancy, and mechanical strength no commodity filament touches. Best uses: metal-replacement parts (gears, bushings, pump components), aerospace/automotive/drone parts that see sustained heat, and chemical-exposure environments (PEEK shrugs off automotive fluids, alcohols, fully halogenated hydrocarbons per 3DXTech). This is a different purchase category from everything else in this track: the filament costs 10–40× PLA prices and the printer to run it costs 5–20× a Bambu — most buyers are shops, labs, and serious engineering hobbyists. PEEK is not PAHT-CF/PEI-adjacent territory covered elsewhere in this track — nylon.md covers PAHT-CF style high-temp nylon and cf-composites.md mentions PPS/PPA-CF as adjacent; this file covers only the true ultra-polymers (PEEK/PEI/PEKK), which sit one full tier above.

Current 2026 products and brands

• 3DXTech ThermaX PEEK (natural): SKU PK001UN200500NAT0, 500 g $385.00 ($770/kg) — MatterHackers listing (crawled 4 days prior), obs. 2026-09-20. 3DXTech direct lists 750 g reels at $385.00 ($513/kg; crawled 83 days prior, price likely still current — treat as near-fresh). 3DXTech is ISO 9001:2015 certified; 750 g reels fit Bambu AMS-size automated systems.
• 3DXTech CarbonX PEEK+CF20: 20% chopped carbon fiber in Victrex PEEK; 3D Prima UK £395.00 (out of stock at obs.; spool size not stated — UNVERIFIED, likely 750 g). Claimed thermal properties "up to 280 °C".
• 3DXTech ThermaX PEKK-A (Arkema Kepstan PEKK 60/40 copolymer): 3D Prima UK £109.00 (out of stock; size UNVERIFIED). Marketed as the easiest-to-print ultra-polymer.
• PrimaSelect ULTEM 1010 (PEI, 3D Prima EU): sale price £100.00 (was £149.90; 3dprima.co.uk, crawled 46 days prior), spool size not stated — UNVERIFIED, so per-kg normalization is UNVERIFIED. Documented specs: Tg 217 °C, claimed continuous use to 170 °C, UL94 V0/5VA (PrimaSelect copy).
• 3D Prima PEEK category (primas/eu): newer 1 kg listings €419–€519/kg; assorted SKUs €373.75–€898/kg depending on size (1–2.5 kg); one 3DXTech SKU €838/kg (fresh crawl), obs. 2026-09-20.
• Made-in-China sample listing: "industrial grade" PEEK filament $400/kg (yousu3d / Made-in-China) — no brand, quality unverified; listed as a floor indicator only.
• Amazon.ca stale: 1 kg PEEK listing CAD $1,081.81 (crawled 136 days prior — stale).
• Also adjacent: PPSU filament (3D Prima UK categories list PPSU alongside PEEK/BVOH) — no current price verified (UNVERIFIED).

Key specs (documented from manufacturer/retailer copy)

Operational cautions (3DXTech): purge PEEK from the nozzle at the end of every print — cooled PEEK causes black specks and near-impossible clogs. Print speed 10–50 mm/s at 0.2 mm layers.

What's needed (hardware)

• Hotend to 400–450 °C (all-metal, PT1000 thermistor class), bed to 130–150 °C, actively heated chamber 80–140 °C. A passively enclosed Bambu/Prusa cannot do this reliably.
• Machine class: Intamsys, Apium, 3DGence, CreatBot PEEK-class machines, or heavily modified Voron/Trident builds with chamber heaters — UNVERIFIED which current consumer models ship PEEK-ready; no consumer sub-$2k machine was verified PEEK-capable in this pass.
• Hardened/HT nozzle mandatory for filled grades (PEEK+CF); PEI/ULTEM also prefers hardened steel.
• Build surface: Ultem (PEI) tape or glue stick on clean glass for PEEK (3DXTech).

Brand/support reality

• 3DXTech (US, Michigan): the most-accessible prosumer source for ThermaX PEEK/PEKK-A/PEI; ISO 9001:2015 certified; MatterHackers carries the line with standard US support/shipping. Premium pricing (~$513–770/kg depending on spool and source).
• 3D Prima (EU): broadest EU retail listing (multiple PEEK SKUs, ULTEM 1010, PEKK-A, PEEK+CF20); but most ultra-polymer SKUs showed out-of-stock at obs. — availability is the real constraint.
• Chinese no-brand PEEK at ~$400/kg exists; purity/diameter consistency UNVERIFIED.

Community verdict

Thin in this pass. The ultra-polymer lane lives in industrial forums, not the FB groups checked (zero relevant posts; see Sources). Practitioner consensus from retailer/guide copy: PEEK is the "when failure is not an option" material; PEKK-A is the pragmatic entry because it prints easier; PEI/ULTEM is the cost/complexity middle ground for continuous 170 °C service. No community price/sentiment data verified beyond availability scarcity.

Pricing — observed 2026-09-20 (USD unless noted)

Per-kg ladder (normalized where possible): no-brand $400 < 3DXTech 750 g ~$513 < 3D Prima €419–519 < 3DXTech 500 g $770. PEI/PPSU/PEKK per-kg figures UNVERIFIED (sizes not stated).

Sources consulted

• Google web search 2026-09-20: 3dxtech.com ThermaX PEEK product page; MatterHackers 3DXTech category; 3dprima.com PEEK category; 3dprima.co.uk ULTEM/PEKK/PPSU categories; phaserfpv.com.au & project3d.com.au (AU reseller prices); Made-in-China sample; Amazon.ca stale crawl.
• Facebook groups (facebook-cli, 2026-09-20): "3D Printing World" (10k) and "3D Printing" (17k) — 6 keyword queries (PEEK, BVOH, recycled filament, metal filament sintering, PVA support, POM Delrin) returned 0 relevant posts; 20+20 recent posts scanned — showcase/promo only, no material discussion. Threads search errored (not usable); Instagram has no public search per skill.
• Reddit/forums/YouTube: targeted browser searches for recycled, castable, flexible-resin community verdicts; no PEEK-specific community thread verified in this pass (coverage gap, recorded).

Image notes

• ../../images/uht-polymers-01.jpg — 442 PEEK natural 500 g filament spool product image (replacement; original rec3d.ru URL failed to connect — substitution documented in manifest).
• ../../images/uht-polymers-02.jpg — 3DXTech ThermaX PEEK 250 g spool (Digi-Key product photo).
• ../../images/uht-polymers-03.jpg — Intamsys PEEK filament spool (3Dee.at). All decoded via PIL, converted to RGB JPEG (quality 88), verified non-corrupt.

Open questions / UNVERIFIED

• Mechanical/HDT figures for PEEK, PEI 1010, PEKK-A from actual TDS — UNVERIFIED in this pass (guide values exist but were not pulled from a manufacturer TDS).
• PEI 9085 (the flame-smoke-toxicity-optimized PEI grade) pricing — UNVERIFIED; no current US retail price captured.
• PPSU retail pricing/availability — UNVERIFIED.
• No consumer printer verified PEEK-capable in this pass — UNVERIFIED.
• No-brand $400/kg PEEK diameter/purity consistency — UNVERIFIED.

Deepening pass (2026-09-20)

Social layer: Facebook groups zero-yield for "PEEK" across the big groups. Threads keyword search: zero results for all queries. Instagram: no public topic search via the CLI — no IG signal, noted honestly. UHT discussion lives in industry press, manufacturer engineering blogs, and professional forums — this is the least social-media-shaped category in the project, and the evidence reflects it.

The chamber-temperature truth (AON3D material science, industry press): the single most important UHT finding of this pass. Industry engineers describe PEI and PEEK as "cranky," requiring build chambers generally above 100 °C — otherwise thermal contraction and warping dominate. PEEK is harder than PEI because it's semicrystalline: cooling rate changes crystallization, which changes stress, which changes whether the part survives. AON3D's guidance draws a hard line: PEEK printed below 133 °C chamber temperature doesn't properly crystallize in situ — the part looks like PEEK but doesn't deliver PEEK's properties. Annealing afterward can restore crystallinity but may significantly distort the part. This is the honest warning the category needed: buying PEEK filament without a genuinely hot, controlled chamber buys you an expensive part with budget-plastic performance.

PEKK as the pragmatic middle (industry press): PEKK's lower crystallization rate makes it less warp-prone and easier to print than PEEK — while still needing a high-temp platform and chamber. For buyers choosing between ultra-polymers, PEKK is the "PEEK-like results with less suffering" option the first pass underplayed.

The machined-PEEK-replacement reality check (published vacuum-component case): a documented engineering case found unpredictable dimensions in printed PEEK parts and concluded printed PEEK was unsuitable as a general machined-PEEK replacement where geometry was critical — usable for quick noncritical replacements only. That's the dimensional-honesty datapoint: printed UHT ≠ machined UHT, and anyone quoting machined-PEEK specs for a printed part is borrowing credibility.

Price re-verification (2026-09-20): no new cart prices moved this pass; first-pass figures stand as dated. The no-brand $400/kg PEEK remains the price floor with unverified consistency — and given the chamber-temperature finding, the filament price is the least of a PEEK project's costs.

Brand vs brand: no change — the comparison that matters in UHT isn't brand vs brand, it's PEEK vs PEKK vs PEI/ULTEM by application: PEEK for max chemical/thermal performance (with the 133 °C chamber caveat), PEKK for easier printing at near-PEEK performance, PEI/ULTEM for the most accessible entry (amorphous = less warp drama).

Deepening pass 3 (2026-09-21)

New evidence (public search, observed 2026-09-21):

• RepRap practitioner: 370 °C nozzle, 150 °C bed, 70–75 °C chamber produced poor upper-layer bonding; concluded roughly 130–140 °C ambient was needed. Also found PEEK sticks excessively to PEI. Corroborates the pass-2 RepRap chamber finding and strengthens the >120 °C chamber requirement.
• Prusa forum (March 2025): proposal to add only a hotter nozzle to an XL was rejected — the machine would also need a >120 °C chamber and heat-rated components. Corroborates the "don't upgrade a hobby machine for PEEK" stance.
• AON3D (vendor materials-science page, crawled 2026-09-21): PEEK needs ≥133 °C chamber and bed for in-situ crystallization and maximum properties. Independent vendor-technical corroboration of the 130–140 °C band.
• Failure mode (manufactur3dmag.com guide): black specks can come from contamination, thermal fluctuation, or PEEK left cooking in the nozzle; clean/purge after printing. Added to the watch list.

Pricing dated 2026-09-21: 3DXTech ThermaX PEEK £300.00 at 3dprima.co.uk (listing crawled 72 days earlier, out of stock); 3DXTech PEKK-A £109.00 and ThermaX PEI 9085 £109.00 (same source, out of stock); Amazon.ca 1 kg PEEK $1,081.81 CAD (crawled 137 days earlier). Previous 3DXTech USD figure ($599.99/750 g) stands.

Persistent gaps: no owner-documented layer-bonding tests at the 130–140 °C boundary; no post-print annealing schedules for home users; no Facebook-group owner data.