FDM Part X High Temperature Polymers

FDM Polymers — A Technical Reference ›

Part X — High-temperature polymers

The high-temperature tier: PPS, the sulfones (PSU, PPSU), PEI, and the PAEK family. PPS-CF is the accessible end — routinely printable on Tier 3 prosumer hardware — while the sulfones and PEI sit at or beyond the Tier 3/4 boundary and PAEK is firmly Tier 4. Where a polymer is out of prosumer reach, these chapters say so explicitly rather than pretending otherwise.

18. PPS, PSU, PPSU, PEI

Four high-temperature engineering polymers that share a hardware tier — Tier 3/Tier 4 boundary hardware (nozzle 300–350 °C, bed 110–150 °C, active chamber 55 °C minimum where the grade specifies one (several PPS-CF products officially print without a heated chamber — see §18.1), >=65 °C for the sulfones, ≥85 °C for PEI (a 65 °C active chamber is demonstrated but marginal)) is mandatory for any of them. The bed and nozzle demands here reach past the §4 Tier 3 envelope (bed <=120 °C), so a fully Tier 3 machine is the practical minimum only for the lower-temperature grades; full Tier 4 (nozzle 380–420 °C, chamber >=85 °C) is required for unfilled PEI and the high-end PSU/PPSU grades. The polymers themselves have nearly nothing else in common: PPS is semi-crystalline with chemical resistance that approaches PEEK at substantially lower processing temperatures; PSU and PPSU are amorphous sulfone polymers with hydrolytic stability and steam-sterilization compatibility; PEI is amorphous with one of the highest glass transitions of any amorphous polymer reaching commercial filament form (217 °C — above PSU, though just under PPSU) and intrinsic flame retardance.

Consumer accessibility note. Open-spool filament for this polymer family is concentrated in CF-reinforced PPS and PEI products, but the unfilled grades are not absent from the open-spool market: 3DXTech sells ThermaX PSU and ThermaX PPSU at retail (~$125 per 500 g — see §18.2), and unfilled ULTEM ships open-spool from 3DXTech (ThermaX PEI 9085), Intamsys, and 3D4Makers, though sealed-cartridge industrial ecosystems (out of scope per Part I §1.2) still account for most unfilled-PEI volume. The consumer-accessible products in this chapter are PPS-CF (multiple brands), PEI (CF-reinforced and limited unfilled), and specialty-tier PSU/PPSU.

18.1 PPS (polyphenylene sulfide)

PPS is an aromatic engineering polymer with a resin RTI of 200–220 °C (printed PPS-CF parts realistically 180–200 °C continuous), chemical resistance to virtually every common solvent and acid below 200 °C, intrinsic flame retardance to UL94 V-0 without additives, and low moisture absorption. Semi-crystalline, T_m ~280 °C, T_g ~90 °C, tensile strength 90–110 MPa (filled grades), modulus roughly 5–12 GPa for printed CF-filled grades (the 10%-CF consumer filaments sit near the bottom of that band — Polymaker Fiberon PPS-CF10 reports about 5 GPa from printed specimens — while higher-CF compounds reach into the low teens), HDT @ 1.8 MPa above 130 °C. The polymer for parts that load mechanically at 150–200 °C continuous, see fuels or oils, or require flame retardance without halogenated additives.

The CF-filled grades are essentially the entire consumer market. Unfilled PPS is challenging to print because the rapid cooling between deposited layers below the polymer's crystallization-onset temperature (~120 °C — a chamber demand beyond the 65 °C Tier 3 ceiling and above even the 85–110 °C entry-Tier-4 chambers of §19.1) produces inconsistent crystallinity that compromises mechanical performance. Carbon-fiber reinforcement at 10–20 wt% suppresses the crystallization shrinkage, gives the matte black surface characteristic of CF-filled polymers, and produces a printable engineering filament. Hardened nozzles are mandatory for the CF abrasion; PPS adds a corrosive-wear component on tooling from sulfur-bearing decomposition species rather than any mechanical abrasion from the polymer itself.

Print process. Nozzle 320–350 °C; bed 80–120 °C; chamber product-dependent rather than family-wide — Polymaker Fiberon PPS-CF10 (bed 80–90 °C) and Flashforge PPS-CF officially print without a heated chamber, while Bambu PPS-CF specifies 60–90 °C; follow the spool TDS. Hardened steel nozzle (PCD preferred for production). Drying is likewise per spool TDS: Bambu specifies 100–140 °C for 8–12 h and Flashforge 120 °C for ≥8 h, so a generic 80–110 °C / 6–8 h cycle under-dries those grades. Bed adhesion: G10 garolite is the engineering default; Magigoo PA also works. On the chamber-spec'd grades, print at the upper end of the chamber range; below 50 °C chamber, interlayer adhesion falls off above ~80 mm Z-height. Annealing at 200 °C for 2–4 h with packed-sand support is recommended for parts that will load at high temperatures; the annealed crystallinity holds the heat envelope.

Brand landscape. Bambu Lab PPS-CF (mid-2024 launch), Polymaker Fiberon PPS-CF10 (10% CF loading documented), Flashforge PPS-CF (LUVOCOM compound), 3DXTech CarbonX PPS+CF, and Raise3D Industrial PPS-CF are among the more widely available consumer-accessible products. Pricing runs $150–280/kg. Polymaker and 3DXTech publish the most detailed TDS data; the Bambu product is the most visible by community adoption. PPS-CF is the right answer when the application loads above 150 °C continuous and PPA-CF (Chapter 14) is not enough.

18.2 PSU (polysulfone) and PPSU (polyphenylsulfone)

Polysulfone (PSU) and polyphenylsulfone (PPSU) are amorphous engineering polymers in the sulfone family — characterized by the sulfone linkage (–SO₂–) in the polymer backbone. Both have very high T_g (PSU ~185 °C, PPSU ~220 °C), exceptional hydrolytic stability (PPSU can survive many repeated steam-autoclave cycles when grade, stress state, and part design are appropriate), and transparent or amber-tinted optical appearance. The polymers behind medical instruments, aircraft cabin parts, and high-temperature plumbing fittings in industrial-scale manufacturing.

Process requirements push above the prosumer envelope. PSU prints at 350–400 °C nozzle, 140–155 °C bed, 65 °C chamber minimum. PPSU prints at 370–410 °C nozzle, 140–155 °C bed, 65 °C chamber. Both numbers cross the upper edge of the Tier 3 envelope this volume defines (350 °C nozzle, 120 °C bed, 65 °C chamber). Consumer hardware that nominally reaches those temperatures often does so unstably; reliable PSU/PPSU printing demands hardware that is also out of scope here. The polymer is in this chapter because it exists in the commercial filament market and consumers ask about it, not because it's a practical choice for prosumer FDM.

Brand landscape. 3DXTech ThermaX PSU and ThermaX PPSU are the consumer-accessible products; pricing $250–500/kg. The realistic procurement path for PSU/PPSU parts is industrial outsourcing or sealed-cartridge industrial printers — both outside this volume's scope. For consumer users encountering an application that calls for PSU or PPSU, the practical alternative is PPS-CF (for the heat envelope); for repeated autoclave service there is no prosumer-printable substitute — PC hydrolyzes under steam sterilization — so outsource the part or redesign around EtO or gamma sterilization.

18.3 PEI (polyetherimide / ULTEM-class)

Polyetherimide is an amorphous high-temperature polymer best known under the SABIC ULTEM trade name — ULTEM 9085 and ULTEM 1010 are the two dominant grades in industrial FDM. Tensile strength 85–105 MPa, modulus 3.0–3.5 GPa, T_g 217 °C for 1010-class neat PEI (186 °C for the 9085 PEI/PC-copolymer blend), HDT @ 1.8 MPa ~153–190 °C (9085-class at the bottom of the range, 1010-class at the top), intrinsic flame retardance to UL94 V-0, very low smoke emission during combustion (the characteristic that drives PEI's aerospace and rail-vehicle adoption). Amorphous, so no crystallization-related dimensional behavior to manage — printed parts are dimensionally consistent.

Process requirements are firmly Tier 4. Unfilled and 1010-class PEI print at 370–420 °C nozzle, 140–155 °C bed, 85 °C minimum chamber; 9085-CF runs a lower nozzle (350–390 °C, Table 18.1) with the same 85 °C chamber floor — 65 °C active chambers are demonstrated but marginal. Drying at 130–150 °C for 4–6 h is mandatory — moisture at print temperatures of 400 °C produces catastrophic flashing inside the melt zone. Hardware capable of these temperatures stably exists but is not consumer-tier.

Consumer accessibility. Open-spool PEI filament accessible to hobbyist users includes CF-reinforced grades — 3DXTech's ship under the CarbonX name (CarbonX PEI 9085+CF), not ThermaX, which 3DXTech reserves for unfilled grades — and unfilled ULTEM from 3DXTech (ThermaX PEI 9085), Intamsys, and 3D4Makers. Sealed-cartridge industrial ecosystems (out of scope) still account for most unfilled-PEI volume. For applications that require true PEI performance (UL94 V-0 with high heat envelope, aerospace certifications, low-smoke combustion), the practical procurement path for consumer users is industrial outsourcing rather than in-house printing. PEI is in this volume primarily for context and to set the boundary of what prosumer FDM can and cannot reach.

18.4 Consolidated comparison

Polymer	Crystallinity	Tg(°C)	Continuous service (°C)	Nozzle (°C)	Consumer access
PPS-CF	Semi-crystalline	90	180–200	320–350	Mainstream consumer; multiple brands
PSU	Amorphous	185	150–170	350–400	Specialty only (3DXTech); above prosumer envelope
PPSU	Amorphous	220	180–200	370–410	Specialty only (3DXTech); above prosumer envelope
PEI 9085-CF	Amorphous	186	170	350–390	Specialty (3DXTech); straddles the Tier 3 / Tier 4 boundary
PEI 1010-CF	Amorphous	217	~170 (RTI)	370–420	Specialty (3DXTech); Tier 4 hardware required
PEI unfilled	Amorphous	217	~170 (RTI)	370–420	Open-spool from 3DXTech, Intamsys, 3D4Makers; Tier 4 hardware required; most volume remains sealed-cartridge industrial

_{Table 18.1 — High-temperature engineering polymer family at a glance. PPS-CF is the only polymer in this group that prints reliably on Tier 3 prosumer hardware; everything else either requires Tier 4 hardware or is locked to industrial-cartridge ecosystems. For consumer users with applications in this thermal envelope, PPS-CF is the practical engineering answer; PEI and the sulfones are aspirational unless industrial hardware or outsourcing is on the procurement path.}

19. PAEK family (PEEK, PEKK)

The polyaryletherketone (PAEK) family is the apex of FDM thermoplastics: continuous-service temperatures around 250 °C, high strength-to-weight at much lower density than metals, chemical resistance approaching PTFE, and — in implant-grade resin formulations — a biocompatibility record behind decades of cleared medical devices. PAEK parts can replace aluminum where heat, chemistry, weight, and specific strength matter more than absolute stiffness; they do not match aluminum's elastic modulus, and FDM parts remain anisotropic and crystallinity-dependent. PEEK (polyetheretherketone) is the volume leader; PEKK (polyetherketoneketone) exists in amorphous and semi-crystalline variants with somewhat lower or grade-dependent T_m. The polymer family is used for engineering metal-replacement in aerospace, automotive, oil-and-gas, and medical applications when those trade-offs are acceptable.

This chapter exists to bound the volume's scope rather than enable consumer PAEK printing. PAEK processing requires nozzle 380–440 °C, bed 140–155 °C, active chamber >=85 °C, drying at 120–130 °C, and post-print annealing for crystallinity. Every line item exceeds the Tier 3 prosumer envelope this volume covers. Consumer-tier FDM hardware labeled as PEEK-capable typically reaches the nozzle temperature briefly and unstably, lacks the active chamber that PEEK crystallinity demands, and produces parts whose mechanical performance is a fraction of the industrial standard. Consumer PAEK printing is possible on small parts with substantial caveats; reliable PAEK printing is not. Hobbyists who need PEEK parts almost universally find industrial outsourcing the practical procurement path.

19.1 PEEK (polyetheretherketone)

Semi-crystalline. T_g 143 °C, T_m 343 °C, tensile strength 90–100 MPa (unfilled), 130–170 MPa (CF-filled), modulus 3.5–4.0 GPa unfilled and up to 12–15 GPa for CF-filled grades, continuous service temperature 240–250 °C. The polymer chemistry has been industrially established since the early 1980s (synthesized 1978, commercialized 1981); the FDM-specific compounding (filament-grade resin processing, diameter tolerance, moisture protection) is a more recent development.

Crystallinity is the dominant printed-part variable. Rapid cooling during FDM deposition produces partially amorphous PEEK with mechanical performance well below the resin spec. Active chamber temperatures of 150–200 °C during printing — industrial-tier territory — produce semi-crystalline parts with the full PEEK envelope. Chamber temperatures of 85–110 °C (already above the 65 °C Tier 3 chamber ceiling — entry-level Tier 4 territory) produce intermediate results that still require post-print annealing (140–200 °C for 2–4 hours) to develop full crystallinity. The annealing step shrinks the part 1–3% and can warp thin walls.

19.2 PEKK (polyetherketoneketone)

PEKK is a PAEK family member differentiated by molecular structure — a different ratio of ether linkages to ketone linkages along the backbone. Commercial PEKK exists in two principal variants: PEKK-A (amorphous, T_g ~165 °C, no T_m, processes amorphously and stays amorphous) and semi-crystalline PEKK (T_g ~165 °C, T_m ~310–340 °C depending on grade, develops crystallinity on cooling and during annealing). Amorphous PEKK processes more easily than PEEK because it does not require active chamber crystallization; semi-crystalline PEKK behaves similarly to PEEK in printing. PEKK is the practical PAEK-family choice for printers that cannot reach PEEK's process temperatures stably.

19.3 Consumer accessibility and brand landscape

Open-spool PAEK filament accessible to hobbyist users clusters around a small set of specialty vendors:

Brand	Products	Notes
3DXTech	ThermaX PEEK; ThermaX PEKK-A (unfilled); CarbonX PEEK+CF; CarbonX PEKK-A+CF15	The US specialty leader for consumer-accessible PAEK; ISO 9001; comprehensive published TDS; pricing $300–500/kg
Polymaker	Fiberon PA12-CF10, formerly PolyMide PA12-CF (positioned as PEEK alternative)	Polymaker does not currently ship a true PAEK product; targets the application space with reinforced polyamide
Flashforge / specialty Asian	PEEK / PEEK-CF (limited)	Available but TDS documentation thin; pricing competitive but mechanical envelope variable
Generic Chinese specialty	PEEK / PEEK-CF	Budget tier with substantial quality variance; mechanical envelope below specialty leaders; appropriate for prototyping only

_{Table 19.1 — Consumer-accessible PAEK filaments. The realistic procurement path for hobbyist PAEK applications is 3DXTech ThermaX PEEK-CF or PEKK-CF on hardware that meets the Tier 4 envelope. Sealed-cartridge industrial PAEK ecosystems (Stratasys F900 with PEKK, industrial Roboze with PEEK) are out of scope. Treat consumer PAEK as a niche specialty filament accessible only to users who have invested in the supporting hardware tier.}

19.4 Application fit

Choose PEEK when: the application requires continuous service above 200 °C with full mechanical performance; the part will be made from an implant- or medical-grade PEEK resin through a qualified, validated process where biocompatibility is a requirement; chemical resistance and thermal endurance together exceed what PPS-CF can deliver; and the supporting hardware tier is available. Choose PEKK when: the application tolerates PEKK's slightly lower thermal envelope (typical 220–240 °C continuous vs PEEK's 250 °C); amorphous PEKK-A is acceptable because post-print crystallization is operationally difficult — the case for PEKK is process simplicity (amorphous-grade handling, relaxed crystallization discipline) rather than cost; PEKK filament typically prices above PEEK.

A caution on medical and implant claims. PEEK's biocompatibility record belongs to specific implant-grade resin grades used in cleared, validated device workflows — not to PEEK filament generically. The first FDA-cleared 3D-printed PEEK implant was cleared as a complete system: a named implant-grade resin, a specified printer, defined modeling software, and a pre-validated production process, with full lot traceability and post-build testing. Regulatory clearance attaches to that device and process, and is granted device-by-device. A part printed from ordinary PEEK filament on prosumer hardware is not an implant and carries no biocompatibility status; treat any medical-contact use as requiring its own qualification against the relevant standards (e.g. ISO 10993) and regulatory pathway.

For most consumer users: PPS-CF (Chapter 18), PPA-CF (Chapter 14), or PA6-CF (Chapter 13) almost certainly meets the application requirement at a fraction of the cost and process discipline. The PAEK family is the right answer when the application requirement is genuinely above what those polymers can deliver, and that boundary is high: continuous service above 200 °C, autoclave compatibility, certain biocompatibility certifications. Below that boundary, choosing PAEK is over-engineering.

---

← Contents · ‹ Part IX — Specialty engineering thermoplastics · Part XI — Support and niche polymers ›