3D Printing Info

Filament comparison

e-TPU vs PA6

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

Foaming / expanded TPU (TPU Aero / TPU Air) guidePA6 (Nylon 6) guide

2 selected · all documented properties

Open these two in the interactive comparisonMore e-TPU comparisonsMore PA6 comparisons
e-TPU vs PA6 — documented properties and sources
PropertyFoaming / expanded TPU (TPU Aero / TPU Air)FLEXPA6 (Nylon 6)PA
Market snapshot
Listing priceUSD/kg; dated snapshots$52.05/kg median; $41.99–$85.29/kg across 6 dated product listings$104.00/kg median; $38.99–$136.00/kg across 3 dated product listings
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 6, ring-opened from caprolactam — the most hygroscopic of the common nylons[2][3]
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)[4][5]1.06 (ISO 1183, 3DXTech iOn PA6 alloy)[6]
Typical priceUSD/kg1 kg-equivalent spools span 42–85; the middle of the market is about 52[7][8][9][10][11][12]1 kg-equivalent spools span 39–136; the middle of the market is about 104, though budget unfilled PA6 has now arrived at 39[13][14]
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[7][8][9][10][11][12][15]39–136 across brands; YXPOLYER 39, 3DXTech iOn Nylon 6 Alloy 104, WearX Nylon 6 136. Unfilled PA6 filament stays rare — most PA6 reaches the market glass- or carbon-filled[13][14]
Market availability1–5Available from several mainstream brands — colorFabb, Recreus, QIDI, Phaetus, Siraya Tech and FusRock all sell an active-foaming TPU[1][7][8][9][11][12]Niche, a handful of specialist brands[13]
Spool sizes & diameters1.75 mm; 0.7, 0.75, 0.8, 1 and 3 kg spools[1][7][9][10][12]1.75 and 2.85 mm; 500 g and 750 g spools[13]
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][10]Wear parts, bushings and gears where PA6's toughness and abrasion resistance matter more than dimensional stability[2]
Diameter tolerance± mm0.03 (Siraya Tech and Roamr, 1.75 mm)[4][5]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][4][5][11]220–260 (Polymaker); 225–265 (Simplify3D)[2][16]
Bed temperature°C30–45 (QIDI and Siraya Tech), 35–50 (Roamr) — a hot bed makes the foamed part over-stick[4][5][11]70–100 (Polymaker); 70–90 (Simplify3D)[2][16]
Enclosure / chamber requirement1–5Open frame is fine — Roamr states no enclosure is required[1][5]Enclosure required (passive)[17][2]
Part cooling fan100 % — cooling sets the foamed structure quickly (Siraya Tech and Roamr)[4][5]Part cooling fan not required (Simplify3D)[16]
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[18][19][4]PEI sheet with a glue stick, or a dedicated adhesive such as Magigoo[16][2]
Maximum volumetric flow (mm³/s; see test conditions)mm³/sUp to 12 (Siraya Tech, Flex TPU Air)[9]Not documented
Bed-adhesion difficulty1–5Not documentedNeeds a specific surface plus adhesive[16][2]
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[4][11]Moderate — retraction tuning needed[2]
Overall printing difficulty1–5Advanced — enclosure, hardware upgrades, tuning; both density and hardness follow nozzle temperature and flow[1]Advanced — enclosure, hardware upgrades, tuning; the filament must be kept dry throughout the print[2][20]
Extruder requirementDirect drive; the base material is a 92A TPU[1][21]Not documented
Hardware Wear & Reliability
Nozzle hardness required1–4Brass fine indefinitely — Roamr states plainly that no hardened nozzle is needed[22][5]Brass fine indefinitely for unfilled grades[2]
Abrasiveness1–5Non-abrasive[22]Non-abrasive when unfilled[2]
Nozzle clog risk1–5Not documentedVery high — frequent jams without careful setup; wet nylon pops and cracks in the melt[23][20]
Heat-creep / jam sensitivity1–5Not documentedModerate — good heatbreak cooling needed[16]
Hotend requirementNo special hot-end required, but a direct-drive extruder is (Simplify3D)[18]May require an all-metal hot end (Simplify3D)[16]
Moisture Behaviour
Moisture absorption (hygroscopicity)1–5Moderate[20]Very high (>2 %) — Polymaker groups nylon with PVA as the most moisture-prone class, and its own PA6-based composites reach 2.35–3.33 % equilibrium[20][24]
Equilibrium moisture content at ~50 % RH%1.09 water absorption (QIDI TPU-Aero; the standard is not stated)[11]Not documented
Drying temperature & time70–80 °C for 4–6 h; keep below 15 % RH while printing (Siraya Tech, Roamr and QIDI)[4][5][11]100 °C for 8 h (Polymaker CoPA); storage below 20 % RH[17][25]
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][4]Popping and cracking during extrusion, then defects that Polymaker describes as very hard to diagnose[23]
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 %[17][23]
Storage requirementSealed with desiccant; often kept in a dryer during the print[20]Sealed below 20 % RH with desiccant; Polymaker says nylon often needs to stay in a dryer while printing[25][20]
Hydrolysis at melt temperatureNot documentedPolymaker requires a 100 °C dry for 8 h and storage below 20 % RH; no molecular-weight loss figure is published, and the published wet data is conditioning rather than melt hydrolysis[17][25]
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][4][11]62 at break (printed XY, ISO 527, 3DXTech iOn PA6 alloy); Stratasys FDM Nylon 6 conditioned to 20 °C / 50 % RH gives 67.6 ultimate and 49.3 at yield printed XZ (ASTM D638)[6][26]
Young's modulusMPa50 unfoamed and 40 foamed (colorFabb, ISO 527-1A)[1]2110 (printed XY, ISO 527, 3DXTech iOn PA6 alloy); Stratasys FDM Nylon 6 conditioned gives 2232 printed XZ and 1817 ZX (ASTM D638)[6][26]
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][4][5][11]9 at break (printed XY, ISO 527, 3DXTech iOn PA6 alloy); Stratasys FDM Nylon 6 conditioned gives 38 printed XZ against 3.2 in ZX (ASTM D638)[6][26]
Flexural strengthMPaNot documented78 (printed XY, ISO 178, 3DXTech iOn PA6 alloy); Stratasys FDM Nylon 6 conditioned gives 97.2 printed XZ and 82 ZX (ASTM D790)[6][26]
Flexural modulusMPa50 unfoamed and 40 foamed flexural modulus (colorFabb, ISO 178)[1]2200 (printed XY, ISO 178, 3DXTech iOn PA6 alloy); Stratasys FDM Nylon 6 conditioned gives 2196 printed XZ and 1879 ZX (ASTM D790)[6][26]
Other impact dataNot documentedIzod notched 106 J/m printed XZ against 43 J/m in ZX; unnotched 2873 against 192 J/m (Stratasys FDM Nylon 6, conditioned 20 °C / 50 % RH, ASTM D256 Method A) — a 15x anisotropy unnotched[26]
Layer adhesion / Z tensileMPaNot documented36.5 ultimate and 28.9 at yield printed ZX (Stratasys FDM Nylon 6, conditioned 20 °C / 50 % RH, ASTM D638)[26]
Brittleness1–5Very ductile — bends far before failing[1]Tough — absorbs impact, yields before breaking[2]
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][4][5][27]Shore D 86 and Rockwell 85 (108) — the source does not name the scales on extruded unfilled PA66 stock (ASTM D2240, D785); no figure is published for a PA6 filament[28]
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[29]Moderate[2]
Fatigue / repeated-flex resistance1–5Excellent — living hinges viable[19]Excellent — living hinges viable[2]
Elasticity / flexibility1–5Rubbery / highly elastic[1]Semi-flexible[23]
Z strength as % of XY%Not documented54 (Stratasys FDM Nylon 6 conditioned, ZX against XZ ultimate tensile, ASTM D638); 59 on the yield figures[26]
Wear resistance & frictionNot documented3DXTech sells a dedicated wear-resistant PA6 grade; abrasion resistance is the usual reason to choose PA6 over PA12[13]
Thermal Properties
HDT at 1.8 MPa°CNot documented93 (Stratasys FDM Nylon 6, conditioned, ASTM D648 at 264 psi)[26]
Glass transition (Tg)°CNot documented105 (DSC, 3DXTech iOn PA6 alloy)[6]
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[4][11]Not documented
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][4]Not documented
Thermal expansion (CTE)µm/m·KNot documented81.0 on extruded unfilled PA66 stock (ASTM D696; source states 4.5e-5 in/in/°F); no figure is published for a PA6 filament, and PA6 and PA66 expand almost identically[28]
Flammability / UL 94Not documentedFlammable; no UL 94 rating published for the unfilled filament grades surveyed[6]
Environment & Chemical
UV resistance1–5Good — years with some colour shift; Polymaker lists UV exposure among the conditions TPU withstands[19]Months outdoors before embrittlement — unstabilised polyamide yellows and chalks under UV[2]
Chemical resistanceWithstands industrial solvents and UV exposure (Polymaker)[19]Withstands oils, fuels and alkalis — the usual reason to choose a polyamide[2]
Water / humidity resistance in service1–5Not documentedAbsorbs water, properties shift — a conditioned part is measurably softer and larger than the same part dry[23][17]
Food contactNot food safe without specific certification (Polymaker)[19]Polymaker notes medical-grade variants exist, but standard filament is not food-contact certified[2]
Biodegradability / compostabilityNot biodegradable[19]Not biodegradable[2]
RecyclabilityNot accepted in household plastic collection[19]Mechanically recyclable but not accepted in household plastic collection[2]
Health & Safety
Fume toxicity1–5Low hazard — minimal VOC and particle emission; TPU was not among the nine filaments in the chamber study[3]Moderate — measurable VOCs and UFPs, ventilation advised[3]
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[3]
Ultrafine-particle emission rateparticles/minNot documented≈2 × 10⁸ median — low for ultrafine particles despite the highest VOC mass of any filament tested[3]
Hazardous species emittedNot documentedCaprolactam, at up to 180 µg/min from nylon filament — the largest single-VOC emission rate measured in the study[3]
Ventilation / filtration requirement1–5Open a window / occasional ventilation[3]Ventilated room or enclosure recommended[3]
Post-Processing
Sanding & machiningDifficult to sand or smooth; Polymaker limits post-processing to trimming or tumbling[19]Sands poorly — the toughness makes it gum rather than powder[16]
Gluing & solvent weldingCyanoacrylate bonds TPU; no common solvent welds it[19]Cyanoacrylate; no common solvent welds polyamide[16]
Vapour / chemical smoothingNo practical vapour smoothing[19]No practical vapour smoothing[16]
Support material pairingPolymaker warns TPU supports are often very difficult to remove[19]PVA dissolves cleanly against nylon; Polymaker sells a break-away PolySupport for PA12[16]
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][4]Parts grow as they absorb moisture after printing; Polymaker declines to publish a standard dimensional allowance because it depends on geometry and infill[23]
Solvents & Solubility
Soluble inDMF, DMSO, NMP and THF dissolve TPU; acetone, MEK and cyclohexanone are partial solvents. All laboratory reagents.[30]Dissolved at 23 °C by formic acid above ~50 %, phenol, m-cresol, 96 % sulphuric acid or hexafluoroisopropanol — laboratory reagents.[31]
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.[30]Zinc chloride solutions stress-crack it — 10 % marginal, 37 % not resistant; alcoholic calcium chloride dissolves it.[31]
Solvent welding & smoothing agentNone practical — the true solvents (DMF, THF, NMP) are laboratory reagents and leave the joint swollen and weak.[30]None — nylon's only solvents are formic acid, phenol and HFIP, all of which degrade the part they wet.[31]

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. 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
  4. Siraya Tech Flex TPU Air Technical Data Sheet Siraya Tech · 2026-08 · tds
  5. Roamr TPU Air HR 80A Technical Data Sheet Siraya Tech · 2026-08 · tds
  6. iOn PA6-based Nylon Alloy Technical Data Sheet v2.0 3DXTech · 2026-08 · tds
  7. Recreus product catalogue Recreus · 2026-08 · vendor
  8. varioShore TPU Natural — product page colorFabb US · 2026-08 · vendor
  9. Siraya Tech Flex TPU Air Black Filament — lightweight foaming flexible, product page Siraya Tech · 2026-08 · vendor
  10. Roamr TPU Air HR 80A Filament — product page Siraya Tech · 2026-08 · vendor
  11. TPU-Aero Lightweight TPU Filament — product page with specification tables QIDI Tech · 2026-08 · vendor
  12. aeFlex TPU-Aero — active foaming low weight TPU, product page Phaetus · 2026-08 · vendor
  13. 3DXTech product catalogue 3DXTech · 2026-08 · vendor
  14. YXPOLYER PA6 Black 1 kg — product page YXPOLYER · 2026-08 · vendor
  15. Phaetus aeWorthy TPU-Aero — reseller listing West3D · 2026-08 · vendor
  16. Nylon — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
  17. PolyMide CoPA Technical Data Sheet V5.4 (dry and wet status blocks) Polymaker · 2024-11 · tds
  18. Flexible (TPE/TPU) — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
  19. TPU — material basics Polymaker Wiki · 2026-08 · doc
  20. Wet Filament — signs, causes and drying Polymaker Wiki · 2026-08 · doc
  21. NinjaFlex 85A Technical Specifications NinjaTek · 2026-08 · tds
  22. Extrudr Product Catalogue (DURAPRO PA12 data block) Extrudr · 2025-03 · tds
  23. Moisture Conditioning — effect on printed nylon properties Polymaker Wiki · 2026-08 · doc
  24. Fiberon PA612-CF15 Technical Data Sheet V1.1 Polymaker · 2024-12 · tds
  25. PolyMide CoPA — Technical Data Sheet page Polymaker Wiki · 2026-08 · tds
  26. FDM Nylon 6 — data sheet (conditioned 20 °C / 50 % RH) Stratasys · 2017-11 · tds
  27. Roamr TPU Air HR 85A Technical Data Sheet Siraya Tech · 2026-08 · tds
  28. TECAMID 66 natural (PA66) — stock shape properties Ensinger · 2026-08 · tds
  29. BambuLab TPU 95A HF vs Qidi TPU 95A HF — results spreadsheet My Tech Fun (Igor Gaspar) · 2024-02 · test
  30. Elastollan — Chemical properties: swelling and chemical resistance BASF · 2026-08 · tds
  31. Ultramid Nylon Chemical Resistance guide (unmodified PA6 B27E and PA66 A27E) BASF · 2026-08 · tds