3D Printing Info

Filament comparison

e-TPU vs PA6/66

Compare printing settings, strength, heat resistance, dated prices and sources.

Foaming / expanded TPU (TPU Aero / TPU Air) guidePA66 (Nylon 66) guide

2 selected · all documented properties

Open these two in the interactive comparisonMore e-TPU comparisonsMore PA6/66 comparisons
e-TPU vs PA6/66 — documented properties and sources
PropertyFoaming / expanded TPU (TPU Aero / TPU Air)FLEXPA66 (Nylon 66)PA
Market snapshot
Listing priceUSD/kg; dated snapshots$52.05/kg median; $41.99–$85.29/kg across 6 dated product listingsNot documented
Identity & Market
Base polymer / chemistryFoaming thermoplastic polyurethane — a blowing agent expands the extrudate so the printed Shore hardness can be tuned by flow rate[1]Polyamide 66, condensed from hexamethylenediamine and adipic acid; melts around 40 °C above PA6[2]
Densityg/cm³1.15 filament (Siraya Tech Flex TPU Air) and 1.05 (Roamr TPU Air HR), ISO 1183; the printed part falls to 0.51–0.93 depending on nozzle temperature (ISO 845)[3][4]1.14 (extruded unfilled PA66 stock)[5]
Typical priceUSD/kg1 kg-equivalent spools span 42–85; the middle of the market is about 52[6][7][8][9][10][11]Not documented
Price range across brandsUSD/kg42–85 across brands; QIDI TPU-Aero 42, Siraya Tech Flex TPU Air 45, Phaetus aeFlex TPU-Aero 49 direct and 40 at West3D, Roamr TPU Air HR 80A 55 at 800 g, Recreus Filaflex Foamy 73 at 750 g, colorFabb varioShore 85 at 700 g[6][7][8][9][10][11][12]Not documented
Market availability1–5Available from several mainstream brands — colorFabb, Recreus, QIDI, Phaetus, Siraya Tech and FusRock all sell an active-foaming TPU[1][6][7][8][10][11]Special order, 1–2 makers worldwide — no unfilled PA66 filament appeared in any catalogue searched, and the 3DXTech nylon range offers PA6, PA12 and a 6/66 copolymer but no straight PA66[13][14]
Spool sizes & diameters1.75 mm; 0.7, 0.75, 0.8, 1 and 3 kg spools[1][6][8][9][11]Not documented
Typical applicationsCushioning, midsoles, insoles and soft-touch parts where the softness needs to vary within one print; Siraya Tech's Roamr line is aimed specifically at printed footwear[1][9]Not documented
Diameter tolerance± mm0.03 (Siraya Tech and Roamr, 1.75 mm)[3][4]Not documented
Printing Parameters
Nozzle temperature°C230–270 (QIDI and Siraya Tech), 220–260 (Roamr); foaming activates near 230 °C and is strongest at the top of the range[1][3][4][10]Not documented
Bed temperature°C30–45 (QIDI and Siraya Tech), 35–50 (Roamr) — a hot bed makes the foamed part over-stick[3][4][10]Not documented
Enclosure / chamber requirement1–5Open frame is fine — Roamr states no enclosure is required[1][4]Enclosure required (passive)[2]
Part cooling fan100 % — cooling sets the foamed structure quickly (Siraya Tech and Roamr)[3][4]Not documented
Bed surface & adhesion aidPEI sheet or painter's tape; Polymaker warns TPU can over-stick and advises a glue stick as a release agent, and Siraya Tech recommends PVP glue or Magigoo as a release agent on PEI[15][16][3]Not documented
Maximum volumetric flow (mm³/s; see test conditions)mm³/sUp to 12 (Siraya Tech, Flex TPU Air)[8]Not documented
Stringing / oozing tendency1–5Severe — the material expands inside the hot end, so it oozes on travel moves; QIDI states retraction tuning cannot fix it and Siraya Tech advises setting retraction distance and speed to zero[3][10]Not documented
Overall printing difficulty1–5Advanced — enclosure, hardware upgrades, tuning; both density and hardness follow nozzle temperature and flow[1]Advanced — enclosure, hardware upgrades, tuning[2]
Extruder requirementDirect drive; the base material is a 92A TPU[1][17]Not documented
Hardware Wear & Reliability
Nozzle hardness required1–4Brass fine indefinitely — Roamr states plainly that no hardened nozzle is needed[18][4]Not documented
Abrasiveness1–5Non-abrasive[18]Not documented
Nozzle clog risk1–5Not documentedVery high — frequent jams without careful setup[19][20]
Hotend requirementNo special hot-end required, but a direct-drive extruder is (Simplify3D)[15]Not documented
Moisture Behaviour
Moisture absorption (hygroscopicity)1–5Moderate[20]Very high (>2 %)[20]
Equilibrium moisture content at ~50 % RH%1.09 water absorption (QIDI TPU-Aero; the standard is not stated)[10]8.5 at saturation on extruded PA66 stock (ASTM D570) — the highest uptake of any polymer in this dataset[5]
Drying temperature & time70–80 °C for 4–6 h; keep below 15 % RH while printing (Siraya Tech, Roamr and QIDI)[3][4][10]Not documented
Symptoms when wetBubbling and popping at the nozzle, stringing and a rough surface; Siraya Tech adds that moisture wrecks the foaming itself, not only the surface[20][3]Not documented
Effect of moisture on strengthPolymaker groups TPU with the highly hygroscopic materials; no dry-versus-conditioned figures are published[20]Measured dry against wet on printed specimens at 6.16 % moisture (Polymaker CoPA): tensile 78.0 → 34.3 MPa, Young's modulus 2703 → 724 MPa, flexural strength 109.8 → 22.6 MPa, while notched Charpy rises 6.9 → 27.7 kJ/m² and elongation 12.7 → 13.2 %[21][19]
Storage requirementSealed with desiccant; often kept in a dryer during the print[20]Not documented
Mechanical Properties
Tensile strength (XY)MPaFalls with foaming: colorFabb 24 unfoamed and 12 foamed (ISO 527-1A); Siraya Tech 10.3 at break printed at 240 °C down to 3.8 at 270 °C; QIDI 6.81 at break (ISO 527, XY)[1][3][10]82.7 at yield and 84.8 at break on extruded PA66 stock (ASTM D638; converted from 12,000 and 12,300 psi) — no printed figure exists because no unfilled PA66 filament was found[5]
Young's modulusMPa50 unfoamed and 40 foamed (colorFabb, ISO 527-1A)[1]2413 on extruded PA66 stock (ASTM D638; converted from 350,000 psi)[5]
Elongation at break%465 unfoamed and 450 foamed (colorFabb, ISO 527-1A); Siraya Tech 629 at 240 °C down to 475 at 270 °C; Roamr 760 down to 540; QIDI 576 (ISO 527, XY)[1][3][4][10]50 at break on extruded PA66 stock (ASTM D638)[5]
Flexural strengthMPaNot documented113.8 on extruded PA66 stock (ASTM D790; converted from 16,500 psi)[5]
Flexural modulusMPa50 unfoamed and 40 foamed flexural modulus (colorFabb, ISO 178)[1]3034 on extruded PA66 stock (ASTM D790; converted from 440,000 psi)[5]
Other impact dataNot documentedIzod 53 J/m on extruded PA66 stock, converted from 1.0 ft-lb/in (ASTM D256)[5]
Brittleness1–5Very ductile — bends far before failing[1]Not documented
Hardness (scale-specific)Shore A / Shore D / RockwellTunable by nozzle temperature: colorFabb 92 Shore A unfoamed; Siraya Tech 78 A printed at 240 °C falling to 63 A at 270 °C, Roamr TPU Air HR 80A 80 A down to 66 A and HR 85A 83 A down to 70 A (ISO 7619)[1][3][4][22]Shore D 86 and Rockwell 85 (108) — the source does not name the scales on extruded PA66 stock (ASTM D2240, D785)[5]
Creep resistance / sustained load1–5Poor — no foamed-grade creep test; a printed 95A TPU bar crept from 74.5 to 82.7 mm over 5 days at 1.25 kg[23]Not documented
Fatigue / repeated-flex resistance1–5Excellent — living hinges viable[16]Excellent — living hinges viable[2]
Elasticity / flexibility1–5Rubbery / highly elastic[1]Semi-flexible[19]
Wear resistance & frictionNot documentedWear factor 200e-10 in3*min/(ft*lb*h) on extruded PA66 stock (ASTM D3702); Ensinger lists very good slide and wear properties[5]
Thermal Properties
HDT at 0.45 MPa°CNot documented232 on extruded PA66 stock (ASTM D648 at 66 psi; converted from 450 °F)[5]
HDT at 1.8 MPa°CNot documented90 on extruded PA66 stock (ASTM D648 at 264 psi; converted from 194 °F) — the gap to the 0.45 MPa figure is the widest in the dataset[5]
Melting point / Vicat°CVicat softening drops as the foam expands: 83 printed at 240 °C to 53 at 270 °C (Siraya Tech, ISO 306); QIDI 70.4[3][10]255 melting on extruded PA66 stock (ASTM D2133; converted from 491 °F)[5]
Continuous service temperature°CNot documented85 long term and 149 short term on extruded PA66 stock (converted from 185 °F and 300 °F)[5]
Annealing responseFoaming activates near 230 °C and expands the extrudate about 1.6×; colorFabb advises dropping flow to 60–70 % to realise the weight saving, and Siraya Tech publishes a flow schedule from 85–90 % at 230 °C down to 50–55 % at 270 °C[1][3]Not documented
Thermal expansion (CTE)µm/m·KNot documented81.0 (extruded PA66 stock, ASTM D696; source states 4.5e-5 in/in/°F)[5]
Flammability / UL 94Not documentedUL 94 V-2 on extruded PA66 stock[5]
Environment & Chemical
UV resistance1–5Good — years with some colour shift; Polymaker lists UV exposure among the conditions TPU withstands[16]Not documented
Chemical resistanceWithstands industrial solvents and UV exposure (Polymaker)[16]Not documented
Food contactNot food safe without specific certification (Polymaker)[16]Not documented
Biodegradability / compostabilityNot biodegradable[16]Not documented
RecyclabilityNot accepted in household plastic collection[16]Not documented
Electrical & ESD propertiesNot documentedVolume resistance 1e15 ohm-cm and dielectric constant 4 on extruded PA66 stock (ASTM D257, D150)[5]
Health & Safety
Fume toxicity1–5Low hazard — minimal VOC and particle emission; TPU was not among the nine filaments in the chamber study[24]Moderate — measurable VOCs and UFPs, ventilation advised[24]
VOC emission rateµg/minNot documentedUp to 180 caprolactam, the dominant VOC from nylon; total VOC reached nearly 200 µg/min, the highest of the nine filaments tested[24]
Ultrafine-particle emission rateparticles/minNot documented≈2 × 10⁸ median — low for ultrafine particles despite the highest VOC mass of any filament tested[24]
Hazardous species emittedNot documentedCaprolactam, at up to 180 µg/min from nylon filament — the largest single-VOC emission rate measured in the study[24]
Ventilation / filtration requirement1–5Open a window / occasional ventilation[24]Ventilated room or enclosure recommended[24]
Post-Processing
Sanding & machiningDifficult to sand or smooth; Polymaker limits post-processing to trimming or tumbling[16]Not documented
Gluing & solvent weldingCyanoacrylate bonds TPU; no common solvent welds it[16]Not documented
Vapour / chemical smoothingNo practical vapour smoothing[16]Not documented
Support material pairingPolymaker warns TPU supports are often very difficult to remove[16]Not documented
Dimensional accuracy & detailFoamed surfaces are matte and textured; holding a consistent hardness means holding the nozzle temperature steady, and the printed density moves by nearly a factor of two across the 230–270 °C window[1][3]Not documented
Solvents & Solubility
Soluble inDMF, DMSO, NMP and THF dissolve TPU; acetone, MEK and cyclohexanone are partial solvents. All laboratory reagents.[25]Dissolved at 23 °C by formic acid above ~80 %, phenol, m-cresol, 96 % sulphuric acid or hexafluoroisopropanol — laboratory reagents.[26]
Softened or crazed byToluene and benzene swell it up to +50 % by weight at 23 °C; the foamed wall soaks up esters and alcohols faster still.[25]Zinc chloride solutions stress-crack it — 10 % marginal, 37 % not resistant; alcoholic calcium chloride dissolves it.[26]
Solvent welding & smoothing agentNone practical — the true solvents (DMF, THF, NMP) are laboratory reagents and leave the joint swollen and weak.[25]None — nylon's only solvents are formic acid, phenol and HFIP, all of which degrade the part they wet.[26]

Material entries describe families or representative grades, not an interchangeable specification for every spool. Test methods, orientations and conditions may differ. Unknown values are marked “Not documented”. Prices and source dates remain historical snapshots; check the linked guide for product details. Differences highlight text, not a universal winner.

Sources for this comparison

  1. varioShore TPU Technical Data Sheet colorFabb · 2026-08 · tds
  2. PA (Nylon) — material basics Polymaker Wiki · 2026-08 · doc
  3. Siraya Tech Flex TPU Air Technical Data Sheet Siraya Tech · 2026-08 · tds
  4. Roamr TPU Air HR 80A Technical Data Sheet Siraya Tech · 2026-08 · tds
  5. TECAMID 66 natural (PA66) — stock shape properties Ensinger · 2026-08 · tds
  6. Recreus product catalogue Recreus · 2026-08 · vendor
  7. varioShore TPU Natural — product page colorFabb US · 2026-08 · vendor
  8. Siraya Tech Flex TPU Air Black Filament — lightweight foaming flexible, product page Siraya Tech · 2026-08 · vendor
  9. Roamr TPU Air HR 80A Filament — product page Siraya Tech · 2026-08 · vendor
  10. TPU-Aero Lightweight TPU Filament — product page with specification tables QIDI Tech · 2026-08 · vendor
  11. aeFlex TPU-Aero — active foaming low weight TPU, product page Phaetus · 2026-08 · vendor
  12. Phaetus aeWorthy TPU-Aero — reseller listing West3D · 2026-08 · vendor
  13. 3DXTech product catalogue 3DXTech · 2026-08 · vendor
  14. Polymaker product catalogue Polymaker · 2026-08 · vendor
  15. Flexible (TPE/TPU) — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
  16. TPU — material basics Polymaker Wiki · 2026-08 · doc
  17. NinjaFlex 85A Technical Specifications NinjaTek · 2026-08 · tds
  18. Extrudr Product Catalogue (DURAPRO PA12 data block) Extrudr · 2025-03 · tds
  19. Moisture Conditioning — effect on printed nylon properties Polymaker Wiki · 2026-08 · doc
  20. Wet Filament — signs, causes and drying Polymaker Wiki · 2026-08 · doc
  21. PolyMide CoPA Technical Data Sheet V5.4 (dry and wet status blocks) Polymaker · 2024-11 · tds
  22. Roamr TPU Air HR 85A Technical Data Sheet Siraya Tech · 2026-08 · tds
  23. BambuLab TPU 95A HF vs Qidi TPU 95A HF — results spreadsheet My Tech Fun (Igor Gaspar) · 2024-02 · test
  24. Emissions of Ultrafine Particles and Volatile Organic Compounds from Commercially Available Desktop Three-Dimensional Printers with Multiple Filaments (Azimi et al.) Environmental Science & Technology 50(3) 1260-1268 · 2016-01 · paper
  25. Elastollan — Chemical properties: swelling and chemical resistance BASF · 2026-08 · tds
  26. Ultramid Nylon Chemical Resistance guide (unmodified PA6 B27E and PA66 A27E) BASF · 2026-08 · tds