3D Printing Info

Filament comparison

e-TPU vs Magnetic

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

Foaming / expanded TPU (TPU Aero / TPU Air) guideMagnetic filament guide

2 selected · all documented properties

Open these two in the interactive comparisonMore e-TPU comparisonsMore Magnetic comparisons
e-TPU vs Magnetic — documented properties and sources
PropertyFoaming / expanded TPU (TPU Aero / TPU Air)FLEXMagnetic filamentSPECIALTY
Market snapshot
Listing priceUSD/kg; dated snapshots$52.05/kg median; $41.99–$85.29/kg across 6 dated product listings$64.99/kg median; $64.99–$64.99/kg across 1 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]PLA loaded with ferromagnetic iron powder, so printed parts respond to magnets[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]About 1.85 (Proto-pasta manufacturer figure) — 1.5× standard PLA[2]
Typical priceUSD/kg1 kg-equivalent spools span 42–85; the middle of the market is about 52[5][6][7][8][9][10]1 kg spools cluster near 65[11]
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[5][6][7][8][9][10][12]64–70 across formats; 1 kg spool 65, 500 g 70, 2 kg 70[11]
Market availability1–5Available from several mainstream brands — colorFabb, Recreus, QIDI, Phaetus, Siraya Tech and FusRock all sell an active-foaming TPU[1][5][6][7][9][10]Niche, a handful of specialist brands[11]
Spool sizes & diameters1.75 mm; 0.7, 0.75, 0.8, 1 and 3 kg spools[1][5][7][8][10]1.75 and 2.85 mm; 0.1, 0.5, 1 and 2 kg spools[11]
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][8]Sensor targets, magnetic fixtures, and props that need to stick to a magnet or rust deliberately[2]
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][9]192 (Proto-pasta)[2]
Bed temperature°C30–45 (QIDI and Siraya Tech), 35–50 (Roamr) — a hot bed makes the foamed part over-stick[3][4][9]60 (Proto-pasta)[2]
Enclosure / chamber requirement1–5Open frame is fine — Roamr states no enclosure is required[1][4]Open frame is fine[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[13][14][3]Not documented
Maximum volumetric flow (mm³/s; see test conditions)mm³/sUp to 12 (Siraya Tech, Flex TPU Air)[7]1.6–2.4 at Proto-pasta's 20–30 mm/s on a 0.4 mm nozzle at 0.2 mm layer[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[3][9]Not documented
Overall printing difficulty1–5Advanced — enclosure, hardware upgrades, tuning; both density and hardness follow nozzle temperature and flow[1]Intermediate — dry filament and a tuned profile; slow, and brittle in filament form[2]
Extruder requirementDirect drive; the base material is a 92A TPU[1][15]Proto-pasta advises an extrusion width 0.05 mm larger than the nozzle and warns feeding is inconsistent below 0.4 mm and on Bowden machines[2]
Hardware Wear & Reliability
Nozzle hardness required1–4Brass fine indefinitely — Roamr states plainly that no hardened nozzle is needed[16][4]Brass acceptable; hardened steel for volume work[2]
Abrasiveness1–5Non-abrasive[16]Moderately abrasive — metal fill[2]
Nozzle clog risk1–5Not documentedModerate — needs dry filament and a clean nozzle; Prusa lists metal-filled composites as a higher clogging risk and recommends a 0.6 mm nozzle minimum[17]
Hotend requirementNo special hot-end required, but a direct-drive extruder is (Simplify3D)[13]Proto-pasta recommends a wear-resistant or larger nozzle for longer service intervals[2]
Moisture Behaviour
Moisture absorption (hygroscopicity)1–5Moderate[18]Not documented
Equilibrium moisture content at ~50 % RH%1.09 water absorption (QIDI TPU-Aero; the standard is not stated)[9]Not documented
Drying temperature & time70–80 °C for 4–6 h; keep below 15 % RH while printing (Siraya Tech, Roamr and QIDI)[3][4][9]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[18][3]Not documented
Effect of moisture on strengthPolymaker groups TPU with the highly hygroscopic materials; no dry-versus-conditioned figures are published[18]Polymaker rates PLA low-sensitivity and publishes no dry-versus-conditioned figures; absorbed water flashes to steam and shows as bubbling and poor layer adhesion[18]
Storage requirementSealed with desiccant; often kept in a dryer during the print[18]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][9]Not documented
Young's modulusMPa50 unfoamed and 40 foamed (colorFabb, ISO 527-1A)[1]Not documented
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][9]Not documented
Flexural modulusMPa50 unfoamed and 40 foamed flexural modulus (colorFabb, ISO 178)[1]Not documented
Brittleness1–5Very ductile — bends far before failing[1]Brittle — Proto-pasta describes the filament as more brittle than standard PLA and needing extra care in handling[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][3][4][19]Not documented
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[20]Not documented
Fatigue / repeated-flex resistance1–5Excellent — living hinges viable[14]Not documented
Elasticity / flexibility1–5Rubbery / highly elastic[1]Rigid[2]
Thermal Properties
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][9]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][3]Not documented
Environment & Chemical
UV resistance1–5Good — years with some colour shift; Polymaker lists UV exposure among the conditions TPU withstands[14]Not documented
Outdoor durabilityNot documentedDeliberately rustable — Proto-pasta markets the iron content as oxidising when exposed to moisture[2]
Chemical resistanceWithstands industrial solvents and UV exposure (Polymaker)[14]Not documented
Food contactNot food safe without specific certification (Polymaker)[14]Not documented
Biodegradability / compostabilityNot biodegradable[14]Not documented
RecyclabilityNot accepted in household plastic collection[14]Not documented
Electrical & ESD propertiesNot documentedFerromagnetic: Proto-pasta states it responds to magnets and behaves similarly to pure iron[2]
Health & Safety
Fume toxicity1–5Low hazard — minimal VOC and particle emission; TPU was not among the nine filaments in the chamber study[21]Low hazard — minimal VOC and particle emission; none of these materials was in the chamber study[21]
Ventilation / filtration requirement1–5Open a window / occasional ventilation[21]Open a window / occasional ventilation[21]
Post-Processing
Sanding & machiningDifficult to sand or smooth; Polymaker limits post-processing to trimming or tumbling[14]Polishing and deliberate rusting are the intended finishes[2]
Gluing & solvent weldingCyanoacrylate bonds TPU; no common solvent welds it[14]Not documented
Vapour / chemical smoothingNo practical vapour smoothing[14]Not documented
Support material pairingPolymaker warns TPU supports are often very difficult to remove[14]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.[22]Chloroform dissolves the PLA matrix and leaves the iron powder behind; laboratory reagent, not workshop stock.[23][2]
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.[22]Acetone and ethyl acetate plasticise the matrix rather than dissolving it; water attacks the exposed iron.[23][2]
Solvent welding & smoothing agentNone practical — the true solvents (DMF, THF, NMP) are laboratory reagents and leave the joint swollen and weak.[22]None — PLA has no workshop-safe solvent, and the iron loading blocks the surface flow smoothing needs.[23]

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. Magnetic Iron PLA — product page and technical data Proto-pasta · 2026-08 · tds
  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. Recreus product catalogue Recreus · 2026-08 · vendor
  6. varioShore TPU Natural — product page colorFabb US · 2026-08 · vendor
  7. Siraya Tech Flex TPU Air Black Filament — lightweight foaming flexible, product page Siraya Tech · 2026-08 · vendor
  8. Roamr TPU Air HR 80A Filament — product page Siraya Tech · 2026-08 · vendor
  9. TPU-Aero Lightweight TPU Filament — product page with specification tables QIDI Tech · 2026-08 · vendor
  10. aeFlex TPU-Aero — active foaming low weight TPU, product page Phaetus · 2026-08 · vendor
  11. Proto-pasta product catalogue Proto-pasta · 2026-08 · vendor
  12. Phaetus aeWorthy TPU-Aero — reseller listing West3D · 2026-08 · vendor
  13. Flexible (TPE/TPU) — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
  14. TPU — material basics Polymaker Wiki · 2026-08 · doc
  15. NinjaFlex 85A Technical Specifications NinjaTek · 2026-08 · tds
  16. Extrudr Product Catalogue (DURAPRO PA12 data block) Extrudr · 2025-03 · tds
  17. Composite materials with metal or wood particles Prusa Knowledge Base · 2026-08 · doc
  18. Wet Filament — signs, causes and drying Polymaker Wiki · 2026-08 · doc
  19. Roamr TPU Air HR 85A Technical Data Sheet Siraya Tech · 2026-08 · tds
  20. BambuLab TPU 95A HF vs Qidi TPU 95A HF — results spreadsheet My Tech Fun (Igor Gaspar) · 2024-02 · test
  21. 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
  22. Elastollan — Chemical properties: swelling and chemical resistance BASF · 2026-08 · tds
  23. Solubility Study of Ingeo Biopolymer Grades in Common Organic Solvents (NWPD003) NatureWorks · 2019-10 · tds