3D Printing Info

Filament comparison

e-TPU vs PLA Silk

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

Foaming / expanded TPU (TPU Aero / TPU Air) guideSilk PLA guide

2 selected · all documented properties

Open these two in the interactive comparisonMore e-TPU comparisonsMore PLA Silk comparisons
e-TPU vs PLA Silk — documented properties and sources
PropertyFoaming / expanded TPU (TPU Aero / TPU Air)FLEXSilk PLAPLA
Market snapshot
Listing priceUSD/kg; dated snapshots$52.05/kg median; $41.99–$85.29/kg across 6 dated product listings$19.49/kg median; $9.75–$24.99/kg across 15 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 with a gloss-forming additive package; suppliers publish the composition as polylactic acid only[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]1.27 (ISO 1183)[2]
Typical priceUSD/kg1 kg-equivalent spools span 42–85; the middle of the market is about 52[5][6][7][8][9][10]Mainstream 1 kg spools cluster near 20[11][12][13]
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][14]10–25 across brands; CHCKX 10 in a 16-roll bundle, SUNLU 13, LANDU 18, YXPOLYER 20, Polymaker 22, Devil Design 25[15][16][17][18][19]
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]Stocked by most mainstream brands[11][15][20]
Spool sizes & diameters1.75 mm; 0.7, 0.75, 0.8, 1 and 3 kg spools[1][5][7][8][10]1.75 mm; 1 and 1.1 kg spools; dual- and tri-colour coextruded variants[21][22]
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]Decorative prints where surface gloss matters more than strength[2]
Diameter tolerance± mm0.03 (Siraya Tech and Roamr, 1.75 mm)[3][4]±0.03 (Bambu Lab)[23]
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]210–240 — 20 °C above the plain PLA window[2]
Bed temperature°C30–45 (QIDI and Siraya Tech), 35–50 (Roamr) — a hot bed makes the foamed part over-stick[3][4][9]35–45[2]
Enclosure / chamber requirement1–5Open frame is fine — Roamr states no enclosure is required[1][4]Open frame is fine[2][24]
Part cooling fan100 % — cooling sets the foamed structure quickly (Siraya Tech and Roamr)[3][4]Fan on[2]
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[25][26][3]Cool Plate SuperTack, smooth PEI or textured PEI[2]
Maximum volumetric flow (mm³/s; see test conditions)mm³/sUp to 12 (Siraya Tech, Flex TPU Air)[7]Not documented
Warping tendency1–5Not documentedNone[2]
Bed-adhesion difficulty1–5Not documentedSticks to anything[27]
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]Easy — minor profile tuning; hotter nozzle and slower cap of 250 mm/s[2]
Extruder requirementDirect drive; the base material is a 92A TPU[1][28]Not documented
Hardware Wear & Reliability
Nozzle hardness required1–4Brass fine indefinitely — Roamr states plainly that no hardened nozzle is needed[29][4]Brass fine indefinitely[24]
Abrasiveness1–5Non-abrasive[29]Non-abrasive[30][24]
Nozzle clog risk1–5Not documentedVery low[24]
Heat-creep / jam sensitivity1–5Not documentedModerate — good heatbreak cooling needed; PLA softens below 60 °C[31]
Hotend requirementNo special hot-end required, but a direct-drive extruder is (Simplify3D)[25]No special hot-end required[27]
Moisture Behaviour
Moisture absorption (hygroscopicity)1–5Moderate[32]Moderate — 0.40 % saturated at 25 °C / 55 % RH[2]
Equilibrium moisture content at ~50 % RH%1.09 water absorption (QIDI TPU-Aero; the standard is not stated)[9]0.40 saturated at 25 °C / 55 % RH (Bambu Lab)[2]
Drying temperature & time70–80 °C for 4–6 h; keep below 15 % RH while printing (Siraya Tech, Roamr and QIDI)[3][4][9]55 °C for 8 h in a forced-air dryer, or 65–75 °C for 12 h on an X1 heatbed[2][33]
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[32][3]Bubbling and popping at the nozzle, stringing, rough surface and weak layers[32]
Effect of moisture on strengthPolymaker groups TPU with the highly hygroscopic materials; no dry-versus-conditioned figures are published[32]Polymaker rates PLA low-sensitivity — the loss shows as poor layer adhesion and brittle layers rather than a published strength figure[32]
Storage requirementSealed with desiccant; often kept in a dryer during the print[32]Sealed with desiccant below 20 % RH; shelf life at ambient is long[34][27]
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]33 (printed XY, ISO 527); eSun Silk broke 22 % below the 16-brand PLA mean on identical 4×4 mm bars[2][35]
Young's modulusMPa50 unfoamed and 40 foamed (colorFabb, ISO 527-1A)[1]2130 (printed XY, ISO 527)[2]
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]2.8 (printed XY, ISO 527) — a quarter of PLA Basic at 12.2[2][34]
Flexural strengthMPaNot documented75 (printed XY, ISO 178)[2]
Flexural modulusMPa50 unfoamed and 40 foamed flexural modulus (colorFabb, ISO 178)[1]2460 (printed XY, ISO 178)[2]
Charpy impact, notchedkJ/m²Not documented10.3 (printed XY, ISO 179, notched); unnotched 18.5[2]
Layer adhesion / Z tensileMPaNot documented25 (printed Z, ISO 527), and flexural Z collapses to 30 against 75 in XY; eSun Silk broke at 12.3 kg where twelve of the 16 plain PLAs managed 44.6–61.5 kg[2][35][36]
Brittleness1–5Very ductile — bends far before failing[1]Brittle — snaps with little warning[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][37]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[38]Poor — no silk-specific creep data published; plain PLA sagged from 12 to 18.7–20.3 mm over 5 days at 1.25 kg[39][40]
Fatigue / repeated-flex resistance1–5Excellent — living hinges viable[26]Poor — no grade-specific S-N curve; plain printed PLA ran 38 000–49 000 cycles at 30 % of tensile strength (R = 0.2)[41][31]
Elasticity / flexibility1–5Rubbery / highly elastic[1]Rigid[2]
Z strength as % of XY%Not documented76 by tensile, 40 by flexural (printed, Bambu Lab)[2]
Thermal Properties
HDT at 0.45 MPa°CNot documented60 (ISO 75, 0.45 MPa)[2]
HDT at 1.8 MPa°CNot documented56 (ISO 75, 1.8 MPa)[2]
Glass transition (Tg)°CNot documented57 (DSC)[2]
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]158 peak melt (DSC); Vicat 66 °C[2]
Continuous service temperature°CNot documented50 — a loaded bar begins to move at this temperature (My Tech Fun, eSun eSilk PLA)[36]
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]50–55 °C for 6–12 h[2]
Flammability / UL 94Not documentedFlammable; no UL 94 rating published by the major brands[34][42]
Environment & Chemical
UV resistance1–5Good — years with some colour shift; Polymaker lists UV exposure among the conditions TPU withstands[26]Degrades within weeks outdoors[31][43]
Chemical resistanceWithstands industrial solvents and UV exposure (Polymaker)[26]Good against weak acids, oils and grease; poor against strong acids and alkalis; dissolved by chloroform, THF and hot benzene[42][31]
Water / humidity resistance in service1–5Not documentedGood — insoluble in water[34]
Food contactNot food safe without specific certification (Polymaker)[26]Base resin is food-contact grade, but printed layer grooves harbour bacteria; Prusa advises against food use[31]
Biodegradability / compostabilityNot biodegradable[26]Industrially compostable only — needs sustained 55 °C; not home compostable[44][31]
RecyclabilityNot accepted in household plastic collection[26]Mechanically recyclable; not accepted in household plastic collection[44]
Health & Safety
Fume toxicity1–5Low hazard — minimal VOC and particle emission; TPU was not among the nine filaments in the chamber study[45]Low hazard — minimal VOC and particle emission[45]
Ventilation / filtration requirement1–5Open a window / occasional ventilation[45]None needed in a normal room[45]
Post-Processing
Sanding & machiningDifficult to sand or smooth; Polymaker limits post-processing to trimming or tumbling[26]Wet sanding — dry sanding heats the surface by friction and smears it[43][31]
Gluing & solvent weldingCyanoacrylate bonds TPU; no common solvent welds it[26]Cyanoacrylate for most joints; some grades partially dissolve and bond with acetone[31][46]
Vapour / chemical smoothingNo practical vapour smoothing[26]No practical vapour smoothing — only chloroform, hot benzene or THF, which are laboratory-only[31]
Support material pairingPolymaker warns TPU supports are often very difficult to remove[26]Support for PLA (Bambu Lab)[2]
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]55° overhangs and 30 mm bridges; gloss hides fine detail and is destroyed by sanding[2]
Solvents & Solubility
Soluble inDMF, DMSO, NMP and THF dissolve TPU; acetone, MEK and cyclohexanone are partial solvents. All laboratory reagents.[47]Chloroform: 10 % w/v in 2–4 h at 23 °C, every grade and morphology; THF and DMF only at 65 °C. Laboratory reagents.[48]
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.[47]Acetone, ethyl acetate and toluene plasticise it but dissolve <1 % even at 65 °C; submersion in acetone crazes and destroys parts.[48][49]
Solvent welding & smoothing agentNone practical — the true solvents (DMF, THF, NMP) are laboratory reagents and leave the joint swollen and weak.[47]Chloroform vapour smooths and welds PLA at the cost of tensile strength; acetone does not smooth it at all.[50][49]

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. Bambu Filament Technical Data Sheet V1.0 — PLA Silk+ Bambu Lab · 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. Panchroma Silk PLA collection Polymaker Shop · 2026-08 · vendor
  12. Spectrum PLA Silk — product listing 3DJake International · 2026-08 · vendor
  13. 3DJake ecoPLA Silk Black 1.75mm 1000g 3DJake International · 2026-08 · vendor
  14. Phaetus aeWorthy TPU-Aero — reseller listing West3D · 2026-08 · vendor
  15. Sunlu Silk PLA+ 1.75mm 1kg Sunlu Official Store · 2026-08 · vendor
  16. Bambu Lab PLA Silk 1.75mm 1kg 3D Universe · 2026-08 · vendor
  17. CHCKX 16 Pack Silk Dual Color PLA Filament Bundle CHCKX (Amazon US) · 2026-08 · vendor
  18. YXPOLYER Silk PLA Black&Gold product page YXPOLYER · 2026-08 · vendor
  19. LANDU Silk Tri-Color PLA Filament 1.75 mm 1 kg LANDU (Amazon US) · 2026-08 · vendor
  20. Overture Silk PLA 1.75mm Overture3D · 2026-08 · vendor
  21. eSUN PLA-Silk Magic 1.75mm eSUN Official Store · 2026-08 · vendor
  22. JAYO Silk PLA+ 1.75mm 1.1kg JAYO Official Store · 2026-08 · vendor
  23. PLA Basic — product page Bambu Lab US Store · 2026-08 · vendor
  24. Filament Material Guide Prusa Knowledge Base · 2026-08 · doc
  25. Flexible (TPE/TPU) — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
  26. TPU — material basics Polymaker Wiki · 2026-08 · doc
  27. PLA — Ultimate 3D Printing Materials Guide Simplify3D · 2026-08 · doc
  28. NinjaFlex 85A Technical Specifications NinjaTek · 2026-08 · tds
  29. Extrudr Product Catalogue (DURAPRO PA12 data block) Extrudr · 2025-03 · tds
  30. Prusament PLA — material page Prusa Polymers · 2026-08 · doc
  31. PLA — material guide Prusa Knowledge Base · 2026-08 · doc
  32. Wet Filament — signs, causes and drying Polymaker Wiki · 2026-08 · doc
  33. Filament Drying Recommendations Bambu Lab Wiki · 2026-08 · doc
  34. Bambu Filament Technical Data Sheet V3.0 — PLA Basic Bambu Lab · 2026-08 · tds
  35. 16 PLA brand comparison test — results spreadsheet My Tech Fun (Igor Gaspar) · 2022-10 · test
  36. Testing eSun PLA filaments: PLA-ST vs PLA+ vs Silk PLA My Tech Fun (Igor Gaspar) · 2026-08 · test
  37. Roamr TPU Air HR 85A Technical Data Sheet Siraya Tech · 2026-08 · tds
  38. BambuLab TPU 95A HF vs Qidi TPU 95A HF — results spreadsheet My Tech Fun (Igor Gaspar) · 2024-02 · test
  39. BambuLab PLA Basic vs PLA Tough vs PLA-CF — results spreadsheet My Tech Fun (Igor Gaspar) · 2026-08 · test
  40. PolyTerra PLA vs PLA+ — results spreadsheet My Tech Fun (Igor Gaspar) · 2026-08 · test
  41. Mechanical Properties of Additively Manufactured Polymeric Materials — PLA and PETG — For Biomechanical Applications Polymers 16(13):1868 · 2024-06 · paper
  42. PolyLite PLA Technical Data Sheet V5.4 Polymaker · 2024-11 · tds
  43. Prusament PLA Technical Data Sheet v1.0 Prusa Polymers · 2018-09 · tds
  44. Filamentive PLA (recycled) — product page Filamentive · 2026-08 · vendor
  45. 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
  46. Prusament rPLA Corn Pigment 1kg — product page Prusa Research · 2026-08 · vendor
  47. Elastollan — Chemical properties: swelling and chemical resistance BASF · 2026-08 · tds
  48. Solubility Study of Ingeo Biopolymer Grades in Common Organic Solvents (NWPD003) NatureWorks · 2019-10 · tds
  49. Improve your 3D prints with chemical smoothing Prusa Research · 2026-08 · doc
  50. Effect of vapour smoothing in trichloromethane on 3D printed PLA — surface, mechanical and chemical structure Pitale, Keche & Chopra, Engineering Research Express 6(4) 045579 · 2024-12 · paper