Clariant Thermoplastic Urethane Black 3D Printer Filament is supplied as an unfilled thermoplastic polyurethane monofilament for fused filament fabrication. The black appearance is achieved by compounding carbon black into the urethane matrix prior to filament extrusion, not by surface painting or post-extrusion dyeing. The product is normally offered in 1.75 mm and 2.85 mm diameters, with dimensional uniformity controlled by two-axis laser micrometer rather than by manual spot gauging. Publicly available product-specific data for this Clariant black TPU designation are limited; the numerical ranges in subsequent sections refer to representative unfilled black TPU filament in the 85A–95A Shore hardness class and should not be read as a Clariant certificate of analysis.

The soft segment chemistry — polyether or polyester — is not always disclosed in the commercial grade name for black TPU filament. This distinction affects hydrolytic stability, oil resistance, low-temperature flexibility, and drying response. A polyester-based urethane typically delivers higher abrasion resistance and better resistance to hydrocarbon oils, while a polyether-based urethane generally retains flexibility at lower temperature and resists hydrolysis in humid environments. The carbon black pigment provides additional UV screening and typically lowers surface resistivity relative to unpigmented TPU; surface resistance should be evaluated by four-point probe under ASTM D257-14 or IEC 62631-3-1 when static dissipation is a design requirement.

Filament manufacturers usually compound carbon black into TPU with a co-rotating twin-screw extruder having an L/D ratio of 36:1 to 44:1, followed by single-screw filament extrusion using a compression ratio of 2.5:1 to 3.0:1. The black masterbatch is metered at a controlled let-down ratio rather than dry blended to avoid agglomerates. On-line laser diameter measurement and closed-loop take-up speed are used to maintain ovality. These processing details are generic to industrial black TPU feedstock; Clariant’s specific compound formulation is confidential.

How does residual moisture affect extrusion pressure and interlayer weld strength?

Urethane filaments absorb atmospheric moisture through polar urethane groups, and moisture levels at equilibrium under 50% relative humidity can reach 0.2 wt% to 0.5 wt% depending on hard segment content and soft segment polarity. Printing without drying is possible only for low-humidity storage conditions; when the water content exceeds roughly 0.05 wt%, the water flashes to steam at the nozzle heated zone, producing intermittent nozzle drool, microporosity in the deposited road, and a measurable reduction in z-direction weld strength. The threshold should be confirmed by Karl Fischer analysis under ISO 15512:2019 if the filament has been exposed to ambient air for more than 24 h or when relative humidity exceeds 60%.

Pre-drying is therefore a process boundary rather than an optional step. A desiccant dryer with a dew point at or below -40 °C and a setpoint of 80 °C for 4 h to 6 h is typical for industrial unfilled TPU filament. The temperature must remain below the softening point of the urethane; exceeding 90 °C may cause filament blocking and irreversible deformation on the spool. Dried filament should be printed from a sealed dry cabinet or a heated hopper mounted to the extruder, because re-uptake of moisture can occur within 60 min to 120 min in an uncontrolled print room. Under these conditions, extrusion pressure remains stable enough to maintain linear mass flow, and the weld line formed between adjacent roads retains more of the bulk tear strength.

For moisture-conditioned filament, the failure signature is not a sudden mechanical break but a gradual rise in extrusion motor current and a visible surface texture change on the outer wall because gas bubbles collapse unevenly during solidification. If an enclosed build chamber is not available, a controlled-purge desiccant column can be placed between the spool and the extruder, but it does not remove moisture already present inside the filament core. The only reliable remedy is full re-drying at 80 °C for an additional 4 h to 6 h, followed by immediate processing.

Print-path mechanics impose a second constraint because the low compressive modulus of urethane filament allows buckling at the drive gear before the material reaches the hot end. A direct-geared extruder with a constrained filament path is preferred; when a Bowden feed is used, the tube should be shortened as much as possible and a low-friction PTFE liner used. Retraction distance should be minimized to 0.8 mm to 2.0 mm at 10 mm/s to 20 mm/s, because long retractions pull soft TPU away from the melt transition region and can produce a void or a surface scar. Extruder idler pressure must be low enough to avoid crushing the filament into an oval cross-section; deformation below the drive gear is a common root cause of inconsistent filament feed. The filament diameter should be re-checked with a micrometer after passing through the extruder if feed slippage occurs.

The nozzle temperature window for unfilled black TPU typically lies between 220 °C and 240 °C. The lower bound is set by interlayer diffusion rather than melting alone; below 215 °C, the melt front at the road-to-road interface cools too rapidly for chain interdiffusion across the weld line, and the part fails at low elongation in the z-direction. The upper bound of 250 °C is set by the onset of hard segment dissociation and discoloration; in a heated build chamber the polymer can remain near that temperature long enough to generate brown decomposition products on the nozzle. Build-chamber temperatures above 40 °C are rarely necessary and may lower the mechanical stiffness of the part during printing. The build plate is generally kept at 20 °C to 60 °C, and part cooling fans are set to 0% to 30% of maximum flow so that the soft road wets the previous layer before solidification.

Print speed for Shore 85A–95A TPU is typically 15 mm/s to 40 mm/s with a 0.4 mm nozzle. Higher speeds require raising the nozzle setpoint closer to 240 °C to 250 °C, which narrows the thermal safety margin. Volumetric flow rate should be limited to roughly 5 mm³/s to 8 mm³/s for consistent melt pressure; published data for this Clariant-specific black grade are limited, so the flow ceiling should be confirmed by measuring filament output over a 60 s extrusion interval and inspecting the printed road for surface melt fracture.

When Black TPU Replaces Acrylonitrile Butadiene Styrene or Polyethylene Terephthalate Glycol in Printed Assemblies

Substitution of rigid feedstocks with black TPU changes part behavior by more than the difference in hardness. An unfilled black TPU in the 85A–95A Shore class has a tensile modulus typically in the range of 10 MPa to 50 MPa, while general-purpose PLA and PETG exhibit tensile moduli near 2.5 GPa to 3.5 GPa; ABS is in a similar rigid range. Consequently, a load-bearing bracket printed from black TPU will deflect two orders of magnitude more under the same load unless the section height is increased or ribs are added. The material is selected for low elastic modulus, repeated flexion, abrasion resistance, and impact energy absorption rather than for dimensional rigidity.

The tensile response is non-yielding and hyperelastic; under ISO 527-2 the material is often reported at break rather than at yield, with representative tensile strength at break of 25 MPa to 45 MPa and elongation at break of 450% to 700% for unfilled Shore 90A TPU. This should be compared with 3% to 8% for PLA and 10% to 30% for ABS. In impact-dominated applications, black TPU dissipates energy through large strain recovery; printed structures can be folded or crushed and return to near original geometry when the strain is below the permanent set limit.

The continuous-service temperature of standard unfilled TPU is not equivalent to that of PETG or ABS. Heat deflection temperature under 0.45 MPa by ISO 75-2/B for the soft TPU class is often below 60 °C to 80 °C, whereas annealed PETG may exceed 70 °C to 80 °C and ABS may exceed 95 °C in heat deflection testing. Hot air, oil immersion, and hydrolytic environments impose additional constraints: polyester-based TPU performs better in contact with nonpolar oils but is more susceptible to chain scission in hot water, while polyether-based TPU tolerates moisture but swells more in fuel-like fluids. Published data for the Clariant-specific black grade under these conditions are limited; compatibility testing should follow ISO 175:2010 or the end-use application specification.

Tear, abrasion and carbon-black surface effects in unfilled urethane feedstock

For applications such as protective bellows, gaskets, cable guides, and sports-equipment pads, the key tests are tear strength, abrasion loss, and compression set. Black TPU in the 85A–95A Shore class typically shows tear strength of 55 kN/m to 85 kN/m when measured under ISO 34-1:2022, method B, procedure (b). Abrasion loss under ISO 4649:2021 method A is commonly reported between 25 mm³ and 60 mm³ for continuous cast or injection-molded TPU, but fused filament fabrication introduces a layer-pattern dependence: the abrasion loss of a printed sample can increase by 20% to 50% relative to a molded plaque because the printed surface contains microgrooves and weld lines perpendicular to the sliding direction. Post-ironing or solvent smoothing is not generally applied to black TPU because the soft matrix responds poorly to acetone or solvent smoothing systems.

The black pigment imposes additional surface and ultraviolet aging behavior. Carbon black functions as a radical trap and ultraviolet absorber, so black TPU typically resists surface embrittlement under ISO 4892-2:2013 accelerated weathering better than natural or light-colored unpigmented TPU. The same carbon black network may reduce electrical surface resistivity from the insulating range to the antistatic or static-dissipative range when the loading is sufficient; however, the conductivity threshold depends on aggregate size, dispersive mixing, and the degree of orientation in the printed road. A four-point probe test under ASTM D257-14 is required to determine whether the filament satisfies a particular electrostatic dissipative specification.

Compression set is also a design limit. For unfilled TPU of Shore 90A, compression set after 24 h at 23 °C under 25% deflection is often 20% to 35%; at 70 °C, the set can exceed 50%. This means a printed seal or cushion does not recover fully after long-term compressive load, especially in warm enclosures. The exact value must be taken from a Clariant product datasheet or from a coupon test conducted under ASTM D395-21 method B, because the 3D-printed structure and void content change the time-dependent recovery.

The following table is a material-class comparison based on representative industrial data for unfilled black TPU, PLA, and ABS feedstocks. It is not a Clariant certificate of analysis.

When the printed part is intended for repeated dynamic flexing, the fused-filament orientation must be aligned with the strain field. The maximum tensile elongation of a black TPU FFF part is substantially lower when tested perpendicular to the layer plane; published data for this specific Clariant configuration are limited, but industrial experience with Shore 90A TPU indicates that z-direction elongation before weld failure may fall to 200% to 350% while xy-direction elongation remains above 450%. A layer height of 0.10 mm to 0.15 mm and a nozzle diameter of 0.4 mm to 0.6 mm typically produce a higher density of weld interfaces but require a longer print time. Without post-extrusion annealing, the weld zones remain the limiting locations under cyclic shear.