-
Notifications
You must be signed in to change notification settings - Fork 1
FDM Part VI Polyamides
FDM Polymers — A Technical Reference ›
The polyamide family in FDM splits cleanly into two tiers: aliphatic nylons (PA6, PA66, PA12, PA612, PA11) — the classic engineering filaments where the dominant variable is moisture; and the semi-aromatic PPA family — where higher Tg, higher HDT, and an order-of-magnitude reduction in moisture sensitivity come at the cost of narrower processing windows and active chamber requirements.
Aliphatic nylons are the original engineering thermoplastics — repeating amide (–CO–NH–) linkages along an otherwise aliphatic backbone, semi-crystalline, with mechanical envelopes that span from PA6's stiff-and-strong-when-dry through PA12's stable-but-modest to the toughness of PA11. In FDM the dominant variable is moisture: the same hydrogen-bonding network that gives nylons their stiffness and crystallinity makes them hygroscopic to a degree that materially changes every process and property number in this chapter. Drying is mandatory, not optional.
Nylons are named by the carbon count of the monomers. PA6 is the homopolymer of caprolactam — a single six-carbon repeating unit. PA66 polymerizes hexamethylenediamine with adipic acid — a six-carbon diamine and a six-carbon diacid. PA12 is the homopolymer of laurolactam, a twelve-carbon ring. PA612 condenses hexamethylenediamine with twelve-carbon dodecanedioic acid. PA11 is the homopolymer of 11-aminoundecanoic acid, derived from castor oil. The carbon count drives the headline property differences: more carbons between amide groups means lower amide density, which means lower moisture uptake, lower melting point, and lower bulk stiffness — but better dimensional stability in humid service.
Co-polyamides (CoPA) — random copolymers blending two or more nylon chemistries, most commonly PA6/PA66 — sit between their parent grades on every axis. CoPA filaments are the most common entry-level nylon SKU in the consumer market and are often what is meant by an unbranded "Nylon" listing.
| Polymer | Repeat unit | Tm(°C) | Sat. moisture (%) | Position in FDM |
|---|---|---|---|---|
| PA6 | caprolactam (C6 amide) | 215–225 | ~8–10 | Strong, stiff, dry; high moisture sensitivity |
| PA66 | HMDA + adipic acid (C6+C6) | 255–265 | ~6–8 | Higher Tm than PA6; rare in filament because Tm pushes the process window |
| PA12 | laurolactam (C12 amide) | 175–180 | ~1.5 | Dimensional-stability default; lower mechanical envelope than PA6 |
| PA612 | HMDA + DDDA (C6+C12) | 210–220 | ~3 | Balance: PA12-like moisture; stiffness intermediate, closer to PA12 than PA66 |
| PA11 | 11-aminoundecanoic acid (C11) | 180–190 | ~1.9 | Toughness-leading; bio-sourced; rare in unfilled filament |
| CoPA | PA6/PA66 random copolymer | 195–215 | ~5–8 | Entry-level; most generic "Nylon" filaments; cosmetic and prototyping |
Table 13.1 — Aliphatic nylon subtypes in commercial FDM filament. The moisture column reports saturation uptake (full immersion / 100% RH equilibrium) per resin TDS data, not printed-part data and not the much lower 50% RH equilibrium value — for PA6 the two differ by roughly 3–4× (saturation ~8–10% vs ~2.5–3% at 50% RH). Printed specimens pick up moisture faster (more surface area, layer-line porosity) but reach similar saturation levels. Skip this table at your peril: matching the wrong subtype to a humid service environment is the most common failure mode in nylon FDM, well ahead of any print-parameter mistake.
The polyamide hydrogen bond is what makes nylons strong and what makes them absorb water. Water molecules insert between amide groups, plasticize the polymer (lowering Tg), reduce stiffness, and increase elongation. The effect is large: PA6 equilibrated at ordinary room humidity loses roughly 60% of its bending modulus relative to its dry state, and its Tg can shift from ~55 °C dry to below room temperature wet. PA12 and PA612, with lower amide density, show much smaller swings (15–35% modulus loss at the same humidity-conditioned state). This is the most important property axis in selecting an aliphatic nylon and is the principal reason the PPA family (Chapter 14) exists at all.
Three practical consequences. First, every nylon TDS quotes "dry as-molded" values unless explicitly labeled as conditioned; planned service should derate those by the appropriate humidity-conditioned factor — using the equilibrium value for the expected service humidity, or the saturation value where the part will be immersed or run continuously wet — unless it will operate in low humidity. Second, filament that has equilibrated with room air will print poorly — the water flashes to steam in the melt zone, producing surface roughness, stringing, micro-bubbles in the bead, and severe layer-adhesion loss. Active drying before printing is mandatory; see §3.5 for the drying-protocol table. Third, post-print conditioning can be exploited deliberately: a PA6 part conditioned to equilibrium in a controlled humid environment trades stiffness for impact toughness and is more dimensionally stable thereafter than the as-printed dry part. Conditioning is a deliberate engineering step in some industrial nylon workflows; the resulting dimensions and mechanical envelope must be characterized empirically.
The table below collects typical FDM-printed values across the dominant aliphatic nylons. Where vendor TDS quote dry-as-printed and wet-conditioned values both, both are shown — the gap is the single most useful number on the page.
| Polymer | Tg dry (°C) | HDT @ 0.45 MPa (°C) | Tensile (MPa) | Modulus (GPa) | Modulus loss dry->wet |
|---|---|---|---|---|---|
| PA6 | ~55 | ~155 | 70–85 dry / 40–55 wet | 2.0–3.0 / 0.8–1.5 | ~60% |
| PA66 | ~70 | ~190 | 75–90 dry / 50–60 wet | 2.5–3.5 / 1.5–2.0 | ~40% |
| PA12 | ~45 | ~145 | 45–55 dry / 40–50 wet | 1.1–1.5 / 1.0–1.3 | ~15% |
| PA612 | ~50 | ~150 | 50–60 dry / 45–55 wet | 1.4–1.8 / 1.05–1.35 | ~25% |
| PA11 | ~45 | ~150 | 50–65 dry / 45–55 wet | 1.0–1.4 / 0.8–1.1 | ~20% |
| CoPA (PA6/66) | ~55 | ~150 | 55–70 dry / 35–50 wet | 1.6–2.4 / 0.8–1.4 | ~45% |
Table 13.2 — Aliphatic nylon FDM property envelope. Dry values are as-printed in a <=15% RH environment; wet values are conditioned to equilibrium at ~23 °C, 50% RH (not full saturation, which would be more severe). The dry-to-wet gap is the engineering signal: PA12 and PA11 are the right choices for parts that will see uncontrolled humidity in service. Confusing dry-only TDS values with field performance is the most common over-promising error in nylon part design.
Carbon and glass reinforcement dominate the commercial nylon filament shelf. Chopped fiber at 10–25 wt% does three things at once: it raises stiffness by 2–4×, suppresses crystallization shrinkage (because fibers do not crystallize and physically restrain the matrix; see §3.2), and reduces moisture-driven modulus loss in absolute terms because the fiber stiffness is unchanged by water. The cost is brittleness — elongation at break collapses to a few percent and unnotched impact drops sharply, even though notched Izod values may hold or improve — and abrasive wear on every contact surface from the extruder gear through the nozzle bore. Hardened nozzles are mandatory; PCD or ruby tips extend useful life from hundreds to thousands of print hours under heavy fiber loading (see §4.1).
CF and GF are not interchangeable. Carbon fiber gives the highest specific stiffness, the lowest density (PA6-CF20 prints at ~1.20 g/cm3 vs unfilled PA6's 1.13), and a characteristic matte black surface. Glass fiber is roughly half the stiffness gain at lower cost, in any color, with substantially better impact retention. For parts where stiffness-to-weight is the binding constraint (drone frames, end-effector tooling), CF wins. For impact-loaded brackets, snap-fit housings, or colored parts, GF is the better trade. Both reduce the moisture gap relative to the unfilled matrix but do not eliminate it: a PA6-CF part still loses substantial wet-state modulus, just from a higher dry starting point. This is the empirical observation that drove the development of PPA-CF — covered in Chapter 14.
Aliphatic nylons share a process envelope at the upper end of Tier 2 hardware (see §4): nozzles 240–290 °C, beds 60–110 °C, passive enclosure beneficial, active chamber not strictly required for the dimensionally stable grades (PA12, PA612, PA11) but recommended for PA6 and PA66 on parts over ~80 mm. Bed adhesion strategy is the second-most-important variable after drying.
| Parameter | PA6 / PA66 | PA12 / PA612 | PA11 | PA-CF / PA-GF |
|---|---|---|---|---|
| Nozzle (°C) | 260–280 | 245–275 | 245–270 | 265–295 |
| Bed (°C) | 90–110 | 70–90 | 60–85 | 90–110 |
| Chamber | passive 40–50 °C | open OK | open OK | passive 40–50 °C; active 55 °C for large parts |
| Part cooling (%) | 0–10 | 0–20 | 0–20 | 0–10 |
| Max volumetric (mm3/s) | 8–12 | 8–14 | 8–12 | 6–10 |
| Pressure advance | 0.030–0.06 | 0.025–0.05 | 0.025–0.05 | 0.04–0.08 |
| Nozzle hardness | brass OK | brass OK | brass OK | hardened mandatory; PCD/ruby preferred |
| Drying | 80–90 °C, 10–16 h | 70–80 °C, 8–12 h | 70–80 °C, 8–12 h | 90–110 °C, 8–10 h |
| Bed surface | G10 garolite, or PEI + PVP / glue | smooth PEI; G10 acceptable | smooth PEI; G10 acceptable | G10 garolite; PEI + Magigoo PA or PVP |
Table 13.3 — Aliphatic nylon process parameters (0.4 mm nozzle starting points). Per-spool calibration on the actual machine is mandatory; the values above are the starting points the polymer chemistry dictates. Skipping the drying row is where most first-time nylon prints fail before any other parameter has a chance to be wrong.
Bed adhesion deserves a paragraph. G10 garolite is the engineering default for PA6, PA66, and any high-warp CF-reinforced nylon: it grips strongly during the print and releases cleanly on full cool-down, with effectively no wear on the garolite sheet. Smooth PEI works for PA12, PA612, and PA11 (lower shrinkage, lower grip needed) and for short prints of PA6 over a glue-stick release layer. Textured PEI is acceptable for PA12-family materials but tends to over-grip PA6 and damage the sheet on removal. Magigoo PA is the dedicated adhesive in the Magigoo family for the nylon class. CryoGrip Glacier — a frost-effect engineered sheet — has been documented as a stable cold-release surface for CoPA at moderate bed temperatures and worth knowing about for prints where standard garolite-on-magnet stacks aren't available.
The aliphatic nylon market has consolidated around a handful of vendors with well-documented engineering-grade SKUs.
| Brand / line | Notable SKUs | Distinguishing notes |
|---|---|---|
| Polymaker Fiberon | PA6-CF20, PA612-CF15, PA6-GF25, PolyMide CoPA | Engineering line built on documented resin grades; 20% CF in PA6-CF20 gives ~8.6 GPa Young's modulus; PA612-CF15 is the practical choice when wet-state retention matters more than maximum stiffness. CoPA targets entry-level nylon use. |
| Bambu Lab | PA6-CF, PA6-GF, PAHT-CF, Support for PA/PET | PAHT-CF is PA12-based (not PPA — see §2.3 and Ch 14); PA6-CF and PA6-GF compete directly with Fiberon. Spool-deformation risk in dryers at the upper drying-temperature range. |
| 3DXTech CarbonX | PA6 + CF, PA12 + CF | US industrial line; ISO 9001 manufacturing; rigorous published TDS data; price 1.5–2× consumer-tier equivalents. |
| Prusament | PA11-CF Carbon Fiber | PA11-CF is rare in the consumer market; bio-sourced PA11 matrix gives the impact-toughness leader among reinforced nylons. |
| Overture | Easy Nylon (CoPA) | CoPA matrix at consumer prices; entry-level toughness; CryoGrip Glacier validated as a compatible build surface. |
| Fiberlogy | Nylon PA12, PA12 + GF | European mainstream; PA12 unfilled in multiple colors; modest mechanical envelope but reliable printing. |
| eSun, Creality, Sunlu | Generic "Nylon" SKUs (CoPA or PA6 base) | Budget tier; specifications often incomplete; suitable for prototyping where mechanical performance is not on the spec sheet. |
Table 13.4 — Aliphatic nylon brand landscape (early 2026). The Polymaker Fiberon line and the Bambu PA-CF / PA-GF / PAHT-CF line are the two most thoroughly documented consumer-accessible product families; 3DXTech CarbonX is the default where industrial qualification is in scope. Cross-brand substitution within a polymer subtype (PA6-CF from Brand A vs Brand B) is not free — fiber loading, matrix grade, and sizing chemistry all shift the printed envelope by 10–25%.
The TDS values collected in Table 13.2 are the right starting point for material selection, but they are not what a printed part will deliver. Independent testing of aliphatic-nylon filaments on controlled, uniform equipment consistently lands below the manufacturers' published numbers, and for this polymer family the shortfall is large enough to change design decisions. This section explains why the gap exists and how to design around it; it deliberately quotes no third-party measured figures, because the reliable independent datasets in this space are published under their owners' terms (see Appendix D.1).
One point of method matters first. Vendors publish two stiffness numbers: a Young's (tensile) modulus and a bending (flexural) modulus, and the headline marketing figure is usually the tensile one - Polymaker's widely quoted "8.6 GPa" for PA6-CF20 is Young's modulus, not flexural. A bending test measures the flexural modulus, so any honest comparison against a bending result must use each datasheet's flexural-modulus figure (ISO 178), XY orientation, dry state — not the larger tensile headline. Mixing the two is a common way to manufacture an apparent agreement, or an apparent scandal, that is really just a units mismatch.
Published bending modulus overstates printed stiffness, and for aliphatic nylons the gap can approach a factor of two. Two effects compound. The first is general to all filled filaments and is the same one §14.11 identifies for polyphthalamides: datasheet modulus is derived from optimally printed, fully dense specimens, while a real part carries layer-line porosity and imperfect fiber alignment. The second is specific to nylons - they are hygroscopic, and unless a specimen is printed bone-dry and tested immediately, absorbed moisture plasticizes the matrix and drops the modulus further. A datasheet specimen is a best case on both counts; a part printed and handled normally is not. The engineering consequence: for aliphatic nylons, do not treat published bending modulus as a 20-30% over-estimate the way one might for a less moisture-sensitive polymer - treat it closer to a ceiling, and design from a conservatively derated value confirmed on your own machine.
Heat figures diverge by method, and unlike modulus they do not err consistently in one direction. Datasheet HDT (ISO 75, a defined-deflection test under a fixed load) and the deformation-temperature tests used by independent reviewers are different procedures, so the two are not expected to match, and observed differences are method variance rather than evidence that a vendor is overstating. The practical lesson is simply that a lone heat number on a datasheet means little without knowing the test behind it. For service-temperature decisions, the continuous-service guidance in Appendix A and the application-fit discussion in §13.8 - built from Tg and HDT together - is a sounder basis than any single published figure.
Brand still moves the result. Two filaments sold under the same nominal class - say, PA6-CF from two different makers - can rank one way on their datasheets and the opposite way once printed and measured. This is the cross-brand variance §13.6 flags: fiber loading, matrix grade, and sizing chemistry shift the printed envelope enough that datasheet stiffness is not a reliable way to rank two products from different manufacturers. Where a vendor reports flexural modulus honestly as an orientation-dependent range rather than a single number - Prusament does this for PA11-CF - that range is itself the most accurate thing the datasheet says about printed stiffness, and no single headline figure should be expected to replace it.
Aliphatic nylons are the right choice when the part will see mechanical loading at modest temperature (under ~80 °C continuous), the service environment is dry or controlled humidity, and the failure mode of interest is fatigue or wear rather than impact spike. Iglidur-class tribological grades (commonly inferred to be PA-based, though igus does not disclose the base polymer) are the canonical wear-bearing application. Drone components and end-effector tooling are the canonical CF-reinforced applications. Cable-management housings and ergonomic grips are the canonical CoPA/PA12 applications.
Aliphatic nylons are the wrong choice when the service environment is uncontrolled humidity and the design depends on stiffness — the modulus loss is catastrophic for PA6 and substantial for PA612 and PA11. PPA (Chapter 14) is the engineering answer to that constraint, at a cost premium and a process-discipline premium. Aliphatic nylons are also the wrong choice when continuous service exceeds 100 °C: PA11 and PA12 creep above their Tg; PA6 holds shape better but loses too much modulus from the moisture interaction. Above 100 °C continuous, the appropriate options are PPA, PC blends with high-PC content (Chapter 15), or - at the high-performance tier - PPS or PEI (Chapter 18).
Polyphthalamide (PPA) is a semi-crystalline, semi-aromatic polyamide: the same amide backbone as the aliphatic nylons of Chapter 13, but with one of the monomers — typically the diacid — replaced by an aromatic ring (terephthalic or isophthalic acid). In its neat industrial resin form the aromatic ring stiffens the chain substantially, raising the glass transition and melting point well above PA6 — the PA6T, PA9T, and PA10T chemistries of Table 14.1 melt between 290 and 325 °C — and reducing saturated moisture absorption to roughly one-fifth of PA6's value. The printable PPA filaments this chapter surveys, however, are not those neat high-temperature resins: to be extrudable on prosumer hardware they are printability-modified to varying degrees, spanning a range from heavily modified copolymers with a markedly lower melting point (commonly 230–260 °C) and a glass transition near 80 °C (e.g. Bambu PPA-CF) to near-resin-class grades (e.g. 3DXTech HTN+CF with Tg 125 °C and FibreX PPA+GF with Tm 305 °C — industrial-tier materials that print far above the prosumer envelope; see §14.6), while keeping most of the moisture-resistance advantage. The reader should hold both facts at once — PPA the resin class is a high-temperature family, but PPA the filament is a moderate-temperature, low-moisture engineering material. The trade for the filament is still a narrower processing window than the aliphatic nylons, active-chamber requirements, hardened-nozzle requirements for the reinforced grades (which is essentially all commercial PPA filament), and a price premium of 2–4× over equivalent aliphatic PA-CF.
"PPA" is an umbrella for several specific semi-aromatic polyamide chemistries, distinguished by the aliphatic diamine paired with the aromatic diacid. The subtype determines the melting point, moisture uptake, and bio-content; filament manufacturers rarely disclose which is in the spool.
| Subtype | Monomers | Tm(°C) | Saturated moisture (%) | Commercial position |
|---|---|---|---|---|
| PA6T/X | hexamethylenediamine + TPA, copolymerized (e.g. PA6T/66, PA6T/6I, PA6T/DT) | ~290–320 | ~2–3 | Dominant industrial PPA chemistry; underlies DuPont Zytel HTN and many compounded filaments. Pure PA6T melts above its decomposition temperature so it always ships as a copolymer. |
| PA9T | nonanediamine + TPA | ~306 | ~2.5–3.2 (24-h uptake 0.17) | Kuraray Genestar® flagship, marketed on its very low 24-hour water uptake; rare in third-party filament. |
| PA10T | decanediamine + TPA | ~316 | ~1.2–1.8 (24-h uptake 0.4) | Partly bio-sourced (decanediamine from castor oil); the lowest saturated uptake in the family. |
| PA4T | butanediamine + TPA | ~325 | n/p (C4 diamine raises amide density) | Newer chemistry, industrialized by DSM; high Tm pushes processing to the very top of Tier 3 hardware. |
Table 14.1 — PPA subtype family. The moisture column reports saturation uptake (immersion equilibrium) on the same basis as Table 13.1; the far lower 24-hour figures that vendors headline are noted in parentheses. Filament TDSs almost never identify which subtype is in the spool; subtype-level identification is generally only possible through DSC analysis or via inference from the reported Tm. Treat the "PPA" label as a chemistry family rather than a single material when comparing spools across vendors.
Compared head-to-head with the aliphatic nylons of Chapter 13, PPA wins on heat resistance, moisture stability, dimensional stability under load, and wet-state mechanical retention; aliphatic nylons win on printability, cost, and unfilled toughness. The wet-state-retention gap is the headline.
| Property | PA6 | PA12 | PA612 | PPA filament (a) |
|---|---|---|---|---|
| Tg(°C) | ~55 | ~45 | ~50 | ~80 |
| HDT @ 0.45 MPa (°C) | 150–170 | 140–150 | 150–160 | 80–230 |
| Saturated moisture (%) | ~8–10 | ~1.5 | ~3 | ~1–2.6 |
| Stiffness loss dry->wet | 60% | 15% | 25% | ~2–3% |
| Print temp (°C) | 260–280 | 245–275 | 245–275 | 280–320 |
| Active chamber | optional | optional | optional | recommended (55–65 °C) |
| Relative filament cost | $ | $$ | $$ | $$$ |
Table 14.2 — PPA vs aliphatic nylons. (a) The PPA column gives FDM filament-grade values: the printable PPA filaments surveyed in this chapter are printability-modified semi-aromatic copolymers with a glass transition near 80 °C, not the neat high-temperature PA6T/PA9T resins of Table 14.1, whose Tm sits at 290–325 °C. The HDT range spans unfilled PPA (~80 °C at 0.45 MPa) through the highest-HDT PPA-CF grades (~210–230 °C at 0.45 MPa; annealed consumer CF grades sit near 190–200 °C, and one GF grade reports 260 °C); see Table 14.5 and Appendix A. The single most consequential row is the fourth: PPA-CF retains the large majority of its dry-state stiffness in humid service, where PA6-CF loses about three-fifths of its bending modulus. The exact wet-retention figure is grade-specific — the near-total retention seen in the Table 14.6 measurements is a Bambu PPA-CF result, not a family constant — but the direction holds across PPA grades. For automotive under-hood parts, outdoor enclosures, and any structural application with uncontrolled humidity, this gap becomes the engineering case for paying the PPA cost premium.
Part I §2.3 introduced the marketing mess: "PAHT" (Polyamide High-Temperature) originally referred to PPA-based filaments around 2020–2022 but has been applied across at least four distinct base polymers. "HTN" (High-Temperature Nylon), used by 3DXTech for the CarbonX HTN+CF product line, is functionally synonymous with PPA at the chemistry level — both refer to semi-aromatic polyamides. The DuPont Zytel HTN trade family is similarly a PPA product line (specifically PA6T copolymers). This chapter consolidates what's known about what each PAHT label actually contains.
| Filament product | Actual base resin | Source / evidence |
|---|---|---|
| Siraya Tech Fibreheart PAHT-CF (pre-2024) | PPA | Rebranded to Fibreheart PPA-CF in late 2024 by the manufacturer; chemistry never changed. |
| Bambu Lab PAHT-CF | Modified PA12 | Distinct from Bambu Lab PPA-CF, which is true polyphthalamide. Both products are sold concurrently. |
| BCN3D PAHT CF15 | Modified high-temperature PA (proprietary) | BCN3D does not publish the base polymer; mechanical envelope places it between PA6-CF and PPA-CF. |
| Qidi PAHT-CF / PAHT-GF | PPA | Packaging explicitly carries "(PPA-CF)" or "(PPA-GF)" parenthetically. |
| Generic Asian-market PAHT-CF | Modified PA6 or PA6/66 copolymers | Inferred from mechanical envelope and price; varies spool-to-spool. |
Table 14.3 — What "PAHT" actually means by vendor (as of early 2026). The filament technical datasheet, not the SKU name, is the only reliable identifier of underlying chemistry. The industry trend since the mid-2024 Bambu PPA-CF launch has been toward explicit "PPA" naming; the legacy PAHT spools continue to circulate in distribution and on retail shelves.
PPA reaches commercial FDM filament in four reinforcement configurations. Carbon-fiber variants dominate shelf space because PPA's strong warp tendency (driven by its high crystallinity, similar to PA6) is largely tamed by fiber reinforcement, where the unfilled grade requires substantially more process discipline. Unfilled PPA is rarer and is currently most accessibly supplied by Siraya Tech Fibreheart PPA.
| Form | Typical loading | Best for | Avoid for |
|---|---|---|---|
| Unfilled PPA | 0% | Wear surfaces, gears, parts requiring impact toughness in addition to heat resistance; tappable threads | Large flat parts (warp without fiber restraint); high-tolerance dimensional work |
| PPA-CF | 10–25 wt% chopped CF | Structural brackets, drone frames, end-effector tooling, automotive under-hood, jigs and fixtures | Cyclic flexural loading (CF creates fatigue-failure planes); tight-tolerance parts unless annealed and conditioned |
| PPA-CF Core | 25% CF (concentrated in filament core), pure-PPA shell | PPA-CF applications where Z-axis layer adhesion is the binding constraint | Multi-material printers requiring uniform filament cross-section; cost-sensitive prints |
| PPA-GF | 10–20 wt% chopped GF | Structural parts where color matters, snap-fit and hinge geometry where CF brittleness causes failures, electronics housings | Maximum stiffness applications (CF wins on modulus); lowest cost (CF and GF are price-comparable) |
Table 14.4 — PPA reinforcement variants. CF-Core is a co-extruded skin-core architecture: a pure-PPA outer shell that promotes Z-axis bonding with itself from layer to layer, around a CF-rich core that carries the in-plane mechanical load. Mixing variants in a single multi-material print risks chamber-compatibility issues (see §14.10).
The table below consolidates published TDS values across the major brands for direct comparison. Values are XY-direction tensile and flexural data from each manufacturer's published datasheet — these are not from a unified independent test. Use them as relative indicators; §14.11 explains why these published figures should be read as a ceiling rather than an expectation.
| Brand · product | Tensile (MPa) | Flex mod. (GPa) | HDT (°C) | Reinforcement |
|---|---|---|---|---|
| Siraya · Fibreheart PPA (unfilled) | 72 | 3.4 | 81 (0.45 MPa) | 0% |
| Siraya · Fibreheart PPA-CF | 98 | 7.4 | 192 (0.45 MPa, anneal) | 15% CF |
| Siraya · Fibreheart PPA-CF Core | 121 | 9.5 | 199 (0.45 MPa, anneal) | 25% CF (core) |
| Bambu Lab · PPA-CF | 168 | ~10 | 227 | ~15–20% CF |
| Bambu Lab · PAHT-CF (PA12-based) | 90 | ~4 | 194 | ~15% CF |
| 3DXTech · CarbonX HTN+CF | 106 | ~7.5–8 | ~195–240 | 15–20% CF |
| 3DXTech · FibreX PPA+GF15 | 115 | ~7 | 260 | 15% GF |
| Raise3D · Industrial PPA CF | 120 | ~7 | ~210 | 15% CF |
| Qidi · PAHT-CF | 110 | 6.9 | ~200 | 15% CF |
| Qidi · PAHT-GF | 85 | ~5 | ~180 | 15% GF |
| Flashforge · PPA-CF (LUVOCOM) | — | ~6 | 220 | 10% CF |
Table 14.5 — PPA filament property envelope (2024–2026 TDS values). HDT is load- and anneal-state dependent and not reported on a single basis by every vendor; where a vendor publishes multiple figures the table gives the 0.45 MPa value with the anneal state noted, and a brand's own datasheet should be consulted for the 1.80 MPa figure. The Bambu Lab PPA-CF flex-modulus figure of ~10 GPa is roughly twice the consumer-tier average, reflecting both higher fiber loading and process-tuned compounding; the price ratio of ~4× over equivalent-chemistry Siraya Fibreheart PPA-CF is real and material to procurement. Wet-state values vary substantially and are documented separately in §14.6 for products where vendors publish them.
Siraya Tech (Fibreheart). Siraya offers the broadest PPA range accessible to consumers. The line consists of Fibreheart PPA (unfilled — originally sold as Fibreheart PAHT), Fibreheart PPA-CF (15% chopped CF, also originally PAHT-CF), and Fibreheart PPA-CF Core (25% CF in a co-extruded core with a pure-PPA shell, launched late 2024). The CF Core product specifically targets the higher-priced tier with what Siraya argues is superior Z-axis layer adhesion through its skin-core architecture. Pricing sits at roughly one-quarter the per-kilogram cost of the highest-priced PPA-CF on the market for nominally equivalent chemistry. Fibreheart PPA is the most accessible unfilled true-PPA filament in the consumer market.
Bambu Lab. Bambu launched its PPA-CF in mid-2024 at a price premium positioned for industrial qualification work. The product TDS publishes the dry/wet property comparison that quantifies PPA's headline value proposition — Table 14.6 below — and is one of the few PPA TDS to do so explicitly. A companion PPA-GF was added in late 2025 / early 2026. Note that Bambu sells two distinct products with similar names: Bambu PAHT-CF (PA12-based) and Bambu PPA-CF (true polyphthalamide); they are not the same filament. PAHT-CF remains in the lineup as a budget option roughly half the cost of true PPA-CF.
| Property (XY direction) | Normal PA6-CF | Bambu PA6-CF | Bambu PAHT-CF | Bambu PPA-CF |
|---|---|---|---|---|
| Bending modulus, dry (MPa) | 4,870 | 5,460 | 4,230 | 9,860 |
| Bending modulus, wet (MPa)* | 1,890 | 3,560 | 3,640 | 9,620 |
| Stiffness decline dry->wet | 61.2% | 34.8% | 13.9% | 2.4% |
| Bending strength, dry (MPa) | 141 | 151 | 125 | 208 |
| Bending strength, wet (MPa)* | 67 | 95 | 115 | 202 |
| Strength decline dry->wet | 52.5% | 37.1% | 8.0% | 2.9% |
| HDT @ 0.45 MPa (°C) | — | — | 194 | 227 |
Table 14.6 — Bambu Lab PPA-CF Technical Data Sheet V1.0, XY tensile/flexural bars, 100% concentric infill. *Wet = sample conditioned to equilibrium at ~25 °C, 55% RH (an in-service humidity state, not full immersion saturation). The 2.4% stiffness decline and 2.9% strength decline for Bambu PPA-CF wet-vs-dry are the empirical case for PPA over PA6-CF in any humidity-exposed application; the 60%+ decline for unfilled-matrix PA6-CF is the principal failure mode this chapter exists to document. The heat row is HDT on the cited test basis, not a continuous max-use temperature; use RTI, creep/load state, humidity, and anneal state for continuous-service design.
3DXTech (CarbonX, FibreX). The Grand Rapids, Michigan industrial line with the longest continuous history of PPA filament production. ISO 9001:2015 manufacturing; HTN terminology rather than PPA in product names but the chemistry is the same family. CarbonX HTN+CF reports Tg 125 °C and heat-resistance/HDT figures up to ~240 °C depending on test method; compare it against PEI only on the same load and method basis. FibreX PPA+GF15 reports HDT 260 °C and Tm 305 °C — and prints accordingly: 3DXTech specifies a 365–390 °C nozzle, 140–160 °C bed, and chamber up to 140 °C, Tier-4 industrial hardware well outside the Table 14.7 window. Prices run 1.5–2× consumer equivalents; this is the default choice when parts will see qualification testing.
Polymaker (Fiberon line — notable absence). Polymaker's Fiberon engineering line is one of the most refined high-temperature filament product families on the market, but as of early 2026 it does not include a true PPA filament. Polymaker has targeted the PPA application space with PA6-CF20 (metal-replacement positioning at moderate cost — see Ch 13 §13.6) and PPS-CF10 (ultra-high-temperature, flame-retardant — Ch 18). The absence of a true PPA-CF leaves a gap that competitors have actively filled. Polymaker typically backfills engineering-resin gaps on a 12–24 month cadence.
Raise3D, Qidi, Flashforge, BCN3D. Raise3D's Industrial PPA CF (15% CF) and PPA GF (15% GF) are sold primarily for their industrial printer line, with a PPA breakaway support filament as a companion product — a useful niche, since most vendors leave PPA users to figure out supports independently. Qidi sells PAHT-CF and PAHT-GF (both PPA-based, with PPA labeling parenthetically on the packaging) at budget pricing; Flashforge uses LUVOCOM® PPA-CF (Lehvoss compound) with 10% CF, reporting HDT 220 °C and unusual non-heated-chamber compatibility for a PPA. BCN3D's PAHT CF15 is shipped primarily for their industrial printer family; the base polymer is undisclosed but the mechanical envelope places it between PA6-CF and PPA-CF.
PPA's narrow processing window — driven by the small gap between melt temperature and degradation onset, and by fast crystallization on cooling — produces less brand-to-brand variation in recommended parameters than most polymer families. Starting points for 0.4 mm hardened-nozzle hardware:
| Parameter | Unfilled PPA | PPA-CF | PPA-GF |
|---|---|---|---|
| Nozzle (°C) | 275–310 | 280–320 | 285–320 |
| Bed (°C) | 70–110 (Siraya: 70–80) | 90–120 | 90–120 |
| Chamber | 40–60 °C preferred | 55–65 °C active recommended | 55–65 °C active recommended |
| Part cooling fan (%) | brand-dependent (Siraya: 20–60) | 0; 5–15% overhangs only | 0; 5–15% overhangs only |
| Print speed (mm/s) | 30–60 | 30–80 | 30–80 |
| Max volumetric (mm3/s) | 7–9 | 8–12 | 8–12 |
| Nozzle hardness | hardened or brass OK | hardened steel mandatory | hardened steel mandatory |
| Nozzle diameter (mm) | 0.4+ | 0.4+ (0.6 preferred) | 0.4+ (0.6 preferred) |
| Bed surface | smooth PEI + glue stick / PVP / Magigoo PC | smooth PEI + glue stick / PVP / Magigoo PC; G10 garolite acceptable | smooth PEI + glue stick / PVP |
Table 14.7 — PPA starting print parameters. The chamber row is the line between marginal and consistent: passive enclosures will print small PPA-CF parts but interlayer bonding falls off above ~80 mm Z-height as the upper-layer temperature drops below the crystallization-onset window. Active chamber is the engineering fix; see §4.3. The table covers the printability-modified prosumer PPA grades only; near-resin industrial grades (e.g. FibreX PPA+GF15: nozzle 365–390 °C, bed 140–160 °C, chamber to 140 °C) print far above this window and are exempt.
PPA filament moisture uptake is grade-dependent: always far below PA6, and ranging from PA12-class to somewhat higher depending on formulation and reinforcement — the carbon-fiber grades sit at the low end, unfilled PPA somewhat above. Moisture symptoms in PPA prints are characteristic: fine stringing despite well-tuned retraction, surface roughness, oozing during travel moves, and — the structural failure mode — micro-bubbles in the wall bead that destroy Z-axis layer adhesion at internal interfaces invisible from the surface.
Drying guidance for PPA varies more by brand than for most filament families, and the chapter's Part I cross-reference should be read as the conservative end of a range rather than a universal requirement. The Part I drying-protocol table (§3.5, Table 3.1) specifies PPA at the high end — up to 100–140 °C for 8–12 hours — which matches Bambu's guidance for its higher-melting PPA-CF and suits the engineering PPA grades; at that upper end a convection oven genuinely outperforms a filament dryer, since filament dryers top out around 80–90 °C in practice. Other current filaments specify a markedly milder protocol: Siraya Fibreheart PPA calls for 80–100 °C for 4–6 hours, and Siraya PPA-CF for 100 °C for 4–6 hours, with both treating drying as needed only when moisture symptoms appear or the vacuum packaging has been compromised. The practical rule is to follow the spool's own datasheet: an 80–90 °C filament dryer is adequate for the Siraya-class grades and for re-drying any opened spool, while the 100–140 °C oven schedule is reserved for the brands that specify it. The upper limit on drying temperature is a spool-substrate limit, not a polymer limit — drying above ~80–100 °C exceeds what most plastic spools tolerate without deforming, so vendors specifying 100–140 °C protocols ship on heat-rated cardboard spools (Bambu's are rated to 145 °C) or expect re-spooling. Cardboard spools tolerate these temperatures but introduce their own debris-shedding problems.
During the print itself: dry-box storage with active desiccant or active heat (low-end filament dryer running at 50–70 °C) is the practical standard. Re-dry any spool that has sat open for more than 24 hours before a serious print.
PPA is semi-crystalline and responds well to annealing: the treatment increases crystallinity, improves HDT and Z-axis strength, and reduces residual stress. Vendor schedules vary, with the more aggressive schedule belonging to Bambu PPA-CF (120–140 °C, 6–12 h). Most consumer PPA-CF responds well to 100–120 °C for 4–6 h with the part supported in packed sand or salt during the heat soak to prevent sag of fine features.
Unfilled PPA anneals too. Siraya Tech markets Fibreheart PPA (unfilled) explicitly as an annealable filament and publishes a protocol — 80–100 °C for 4–8 hours with a natural cool-down in the oven — citing HDT, mechanical, and dimensional-stability gains (see Part I §3.6). Without fiber reinforcement the warp risk during the heat soak is higher than for the CF and GF variants, so support the part in packed sand or salt and favor robust geometries; but the vendor guidance is to anneal, not to avoid it.
Two PPA-specific failure modes emerge on multi-extruder hardware that do not appear on single-extruder Tier 3 setups.
Filament brittleness inside the filament path. PPA-CF — especially at the higher fiber loadings — is brittle enough on the spool that bent filament paths can snap it inside PTFE tubes. PA6-CF tolerates this; PPA-CF does not. On hardware with a moving toolhead that flexes the filament tube as it returns to its home position, the tube bending angle near the toolhead is the failure point. Practical mitigations: route the filament through whichever toolhead experiences less tube-bending stress (typically the fixed-position rather than the lifting hotend on dual-hotend systems); re-route the PTFE tube into the largest practical bend radius, relieving any twist set, before printing PPA-CF; or feed the filament from a dry box mounted close to the toolhead to minimize the tube path length entirely. Vendor documentation on this point is concentrated in the printer-specific guides rather than the filament TDS.
Abrasive-nozzle compatibility with offset calibration. Hardened steel, ruby, tungsten carbide, and PCD-tipped (E3D Diamondback) nozzles are all engineered for the fiber-loaded PPA application. PCD tips are electrically non-conductive, so printers that locate the nozzle by electrical contact with the bed cannot detect the tip — the metal nozzle body and the cobalt binder in the PCD compact still register on inductive or eddy-current sensors — requiring load-cell, mechanical, or camera-based offset calibration instead; this is mentioned in §4.1 and becomes operationally relevant when switching from an aliphatic-nylon nozzle to a PPA-grade nozzle mid-spool.
Multi-material chamber compatibility. PPA-CF qualifies as a high-temperature filament in every vendor's compatibility scheme. It cannot be combined with low-temperature filaments (PLA, PETG, soft TPU) in the same print: the chamber and bed temperatures required for PPA-CF will soften and warp those materials. Compatible-tier filaments include other engineering-grade nylons (PA6-CF, PAHT-CF, PA-GF), ABS, ASA, PC blends, PET-CF, PPS-CF, and ABS-GF. Compatible support filaments are limited; PPA-specific breakaway supports (notably the Raise3D Industrial PPA breakaway line) and same-material soluble strategies are the practical options.
Every value in Table 14.5 comes from a manufacturer's datasheet. Independent testing of PPA-class filaments on controlled, uniform equipment shows those datasheet figures should be read with the same caution §13.7 applies to the aliphatic nylons. This section describes the patterns that recur across the PPA family without reproducing any third-party measured numbers; the reliable independent datasets in this space are published under their owners' terms (see Appendix D.1).
Flexural modulus is consistently overstated. Across PPA-class products, printed-part stiffness measures below the datasheet figure, and the gap tends to be widest on the highest claims. This is not specific to one brand: TDS modulus is typically derived from injection-molded or optimally-oriented specimens, while a printed part carries layer-line porosity and imperfect fiber alignment. Treat published modulus as a ceiling rather than an expectation, and derate it by roughly 20-30% for design - then confirm against a specimen printed and conditioned the way the real part will be.
Heat figures diverge by method, not always by direction. Datasheet HDT and the deformation-temperature tests used by independent reviewers load the specimen differently, so the two are not expected to match - a product can measure above its TDS heat figure on one test and below it on another without either number being wrong. The takeaway is that a single heat number on a datasheet means little without knowing the test behind it. For service-temperature decisions, the continuous-service guidance in Appendix A and the application-fit discussion in §14.12 - built from Tg and HDT together - is a sounder basis than any single published figure.
Diminishing returns above ~20% fiber loading. A pattern worth carrying into product selection, and consistent with the §14.6 discussion: once carbon-fiber loading rises past roughly 20%, measured stiffness tends to plateau while brittleness keeps increasing. A 25%-loaded grade does not reliably out-stiffen a well-made 20% grade in a printed part, so a higher headline loading on the datasheet is not by itself a reason to choose one PPA-CF product over another. As with the nylons, fiber loading, matrix grade, and sizing chemistry mean datasheet stiffness is not a dependable way to rank products from different makers; where independent data exists it is most useful as a cross-check on the relative ranking, not as a substitute for testing on your own machine.
Choose PPA when: continuous service exceeds 100 °C and a reinforced grade is used (engine-bay brackets, manifolds, oven-adjacent fixtures — PPA-CF and PPA-GF carry the heat, while unfilled PPA filament tops out near its ~75–85 °C HDT and is not the grade for sustained high-temperature load); exposure to fuels, oils, glycols, or aggressive cleaners is expected (PPA outperforms PA6 in sustained hot-glycol, hot-oil, and salt exposure, though PA6 itself tolerates fuels and oils well at moderate temperatures); outdoor parts need to retain stiffness through winter humidity (PA6-CF loses >60% modulus wet, while in Bambu's published dry-versus-wet test its PPA-CF lost only ~2%); mechanical parts under load see wear, fatigue, or dimensional-stability requirements; strength-to-weight is the binding constraint (drone frames, end-effector tooling); under-hood automotive replacement parts are in scope.
Avoid PPA when: the part is aesthetic or cosmetic (PPA-CF is black-only with matte surface finish, and the cost is unjustified); service stays at room temperature (PETG, PCTG, or PA612 will print more reliably for the same mechanical envelope at one-third the cost); cyclic flex is required (CF reinforcement creates fatigue-failure planes; an unfilled engineering nylon - PA12, PA11 - or PCTG is more forgiving); the design is still iterating (the printability tax is real; a $200/kg material is a lot to spend on parts that may be revised 5-10 times before freeze).
Adjacent alternatives worth considering. PA612-CF15 captures most of the wet-state-retention benefit at lower cost and easier printing - a strong middle ground if PPA's full heat tier is not required. PA6-CF and PAHT-CF are appropriate when service temperature stays below 80 °C and cost matters. PPS-CF (Chapter 18) is the next tier up for parts seeing >200 °C continuous and is flame-retardant - a different polymer family, more demanding to print, but reaching temperatures PPA cannot. PEEK and PEKK (Chapter 19) are the tier above that, requiring Tier 4 hardware outside this volume's scope.
← Contents · ‹ Part V — Polyolefins · Part VII — Polycarbonates ›
FDM Polymers — A Technical Reference
- Part I — Foundations
- Part II — PLA Family
- Part III — Polyester Family
- Part IV — Styrenics Family
- Part V — Polyolefins
- Part VI — Polyamides
- Part VII — Polycarbonates
- Part VIII — Thermoplastic elastomers
- Part IX — Specialty engineering thermoplastics
- Part X — High-temperature polymers
- Part XI — Support and niche polymers
- Part XII — Cross-cutting workflows
- Appendices
- Source manifest