TPU (Thermoplastic Polyurethane)

polymer

elastomeric thermoplastic block copolymer

Thermoplastic polyurethaneNinjaTek CheetahNinjaTek NinjaFlexFilaflexeSUN eTPURecreus FilaflexFlexible filamentTPE-U

TPU (Thermoplastic Polyurethane) 3D printed component

Density

1.22 g/cm³

UTS (FDM as-built (XY, Shore A 95 — NinjaTek Cheetah equivalent))

22–36 MPa

Elongation (FDM as-built (XY, Shore A 95 — NinjaTek Cheetah equivalent))

400.0–700.0 %

Elastic modulus

0–0 GPa

Glass transition (Tg)

-45–-25 °C

Max service temp

70–90 °C

Mechanical & thermal properties — 2 conditions

Property	FDM as-built (XY, Shore A 95 — NinjaTek Cheetah equivalent)	FDM as-built (Z — upright)
Elastic modulus	0–0 GPa	—
Ultimate tensile strength	22–36 MPa	12–24 MPa
Elongation at break	400.0–700.0 %	150.0–400.0 %
Density	1.20–1.25 g/cm³	—
Glass transition (Tg)	-45–-25 °C	—
Max service temperature	70–90 °C	—

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Engineering considerations

Extruder selection is the primary constraint: verify direct-drive capability before specifying TPU. Most common desktop printers (Bambu Lab, Prusa, Creality with direct-drive kit) handle Shore A 95 TPU reliably. Softer grades (Shore A 83–87) require optimised direct-drive setups. Bowden systems (basic Ender 3, Anet A8) are not suitable.
Shore hardness grade selection: Shore A 83–87 (NinjaFlex-type): extremely soft, high elongation, harder to print. Shore A 95 (Cheetah-type): semi-flexible, easier to print, good for gaskets and grips. Shore A 98+: near-rigid, easiest to print but limited flexibility. Match hardness to application stiffness requirement.
Print speed matters for properties: guo-2018-tpu-fdm shows that print speed above 30 mm/s reduces inter-layer adhesion and elongation. For structural flexible parts, print at 15–25 mm/s. Faster speeds acceptable for visual/non-structural parts.
Infill pattern design for flexible structures: for custom compliance in flexible mechanisms, use lattice infill (gyroid, honeycomb) to engineer the part's effective stiffness. A 20% gyroid infill creates a part with 5–10× lower effective modulus than solid. This is more controllable than varying Shore hardness.
Compression set and creep: for sealing applications, design with 10–20% initial compression pre-load to account for long-term compression set. TPU seals lose sealing force over time under sustained compression. Replace seals in high-cycle or long-duration applications after performance validation.
Chemical compatibility: verify TPU compatibility with specific chemicals. Most grades resist oils, hydraulic fluid, and moderate fuels. Avoid concentrated strong acids/bases, aromatic solvents (toluene, xylene), and chlorinated solvents. Medical-grade TPU: verify ISO 10993 biocompatibility testing for device-contact applications.
Multi-material FDM (TPU + rigid): dual-extrusion systems can overmould TPU onto PLA or PETG rigid scaffolds, creating soft-touch grips or compliant joints with rigid structure. Interface adhesion between TPU and PLA/PETG is moderate — mechanical interlocking features (undercuts, dovetails) improve joint strength.

Advantages

Extreme elongation (400–800%): TPU stretches repeatedly and returns to original shape — no other common FDM polymer approaches this ductility
Cold temperature flexibility: remains elastic to –35°C and below, unlike rigid FDM polymers that become increasingly brittle near 0°C
Good abrasion resistance: TPU resists abrasive wear better than most rigid thermoplastics — ideal for sliding contacts, wear pads, and shoe soles
Chemical resistance: resists oils, greases, and many fuels better than PLA/PETG. Suitable for hydrocarbon-contact sealing applications
Biocompatible grades available: many TPU formulations are biocompatible (USP Class VI, ISO 10993) for skin-contact and short-term body contact
Acoustic and vibration damping: TPU's viscoelastic nature damps vibrations effectively — useful for isolation mounts and machinery bases
Printable with standard FDM equipment (direct drive): no specialised machine needed — direct drive extruder printers handle most TPU grades

Limitations

Direct-drive extruder required: Bowden setups (where the motor is remote from the hot end) cannot reliably extrude TPU — the flexible filament buckles in the Bowden tube. Only direct-drive printers are practical for standard TPU grades
Slow print speed required: maximum print speed ~20–30 mm/s to avoid extrusion inconsistency. Significantly slower than rigid filaments (PLA 60–100 mm/s) — long build times for any non-trivial part
No effective post-processing: TPU cannot be solvent-smoothed, easily sanded, or chemically treated. Surface quality is limited to as-printed state. No standard painting — most coatings crack on flexible substrates
Not as stiff as structural thermoplastics: E ~26 MPa vs PLA 3500 MPa. TPU is not a structural material — it is an elastomeric material for flexibility, sealing, and damping applications only
Stringing and oozing: TPU is highly prone to stringing at high temperatures or with retraction. Requires careful calibration: lower retraction distance, minimal travel speed, and accurate temperature control
Hygroscopic: TPU absorbs moisture, causing print quality problems and potential hydrolysis in humid environments. Dry at 50°C for 4–6h before printing. Seal parts in humid environments
Long-term creep: under sustained compressive load, TPU creeps. For static sealing applications, account for long-term compression set in design (typically 10–30% after extended loading)

Typical applications

Gaskets, seals, and o-ring profiles where standard cross-sections are impracticalVibration dampeners, anti-slip pads, and isolation mountsFlexible grips, handles, and overmould-style covers for rigid partsMedical device tubing models and anatomical compliant structuresShoe sole prototypes, custom orthotics, and prosthetic socket linersCable strain relief and protective sleevesFlexible hinges and living-hinge designs requiring high cycle lifeSoft robotic actuators and grippers (with designed compliance and porosity)Wearable devices and body-conforming structuresSports equipment protective components and padding

TPU (Thermoplastic Polyurethane)

Mechanical & thermal properties — 2 conditions

Engineering considerations

Advantages

Limitations

Typical applications

Industries

Standards & certifications

Compatible AM processes (1)

Other polymer materials

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