The Huntsman Iroprint™ F 80112 polyester-based thermoplastic polyurethane prototyping filament is supplied as a flexible fused filament fabrication feedstock in 1.75 mm and 2.85 mm diameter formats, with diameter variation controlled to ±0.05 mm. The polyester soft segment places the material in the Shore 85A–90A hardness band and gives the printed solid a combination of high elongation, tear strength, and abrasion resistance. Because the melt is thermoplastic, parts can be built on open-material FFF machines without ultraviolet post-curing or solvent debinding. The material is distinguished from polyether TPU grades by its higher tensile modulus, better oil and fuel resistance, and lower hydrolytic stability; these distinctions become important when a prototype is tested under mechanical load or exposed to hydrocarbons. All numerical values in this document are typical values from supplier documentation or standard polyester TPU processing practice and must be confirmed against the current Huntsman datasheet for lot-specific acceptance testing.

What Changes When a Polyester-Based TPU Enters the Fused Filament Fabrication Flow Path?

Polyester-based TPU filament does not behave like rigid PLA or PETG in the extruder. At the molecular level, polyester soft segments formed from adipic acid esters provide hydrocarbon resistance and mechanical strength, while the hard segments form hydrogen-bonded urethane domains that act as physical crosslinks. In the melt phase these domains disassociate at processing temperature; during cooling they re-form and set interlayer strength. A practical consequence is that the material remains flexible and low-modulus in the feed path, so columnar buckling can occur if the unsupported filament path is too long. In a direct-drive extruder with a constrained filament path and a 0.4 mm brass or hardened-steel nozzle, stable feeding is observed at print speeds of 20–40 mm/s. Higher feed rates above 50 mm/s tend to increase melt pressure above 3–4 MPa, producing volumetric inaccuracies and surface defects. In a 0.4 mm nozzle at 230°C, the apparent wall shear rate for a 1.75 mm filament at 30 mm/s is on the order of 10⁴ s⁻¹; under these conditions the melt is in the shear-thinning region, which reduces die swell and improves detail resolution. The recommended heated bed set point is 40°C–60°C; below 30°C, warping of low-modulus parts may occur, while above 70°C, the first layer can distort under its own weight. Layer heights from 0.10 mm to 0.20 mm are practical; 0.05 mm layers require a hardened nozzle and reduced speed to avoid clogging.

Retraction is a critical control variable. Flexible TPU stores elastic energy in the filament path between the drive wheel and heat break, and aggressive retraction can expel the filament laterally rather than pulling it cleanly from the melt zone. Retraction distance should be kept below 2.0 mm at 20 mm/s; higher retraction pulls air into the nozzle and can create intermittent extrusion. A field failure observed on open-frame direct-drive machines is filament bird-nesting between the drive gear and heat break when retraction is set above 3 mm. The stored elastic energy releases laterally and the filament wraps around the knurled drive wheel. A full filament path liner and retraction below 2 mm mitigate this failure.

The extruder barrel set point should be 220°C–240°C. Below 210°C, interlayer fusion is incomplete and z-direction tensile strength decreases; above 250°C, thermal degradation can proceed through urethane bond cleavage, producing yellowing and melt-strength loss. Fan cooling is usually set to 30–50%. Full fan output is not required for large flat parts and may induce curl in sharp corners. A heated chamber is not mandatory, but an ambient chamber temperature of 20°C–30°C lowers thermal shock and reduces warping in thin-walled parts.

Drying, Storage, and Feed-Path Failure Modes

Before printing, drying is mandatory. Amine-free, desiccant or forced-air drying at 80°C for 3 h is recommended when the filament has been out of vacuum-sealed packaging for more than 24 h or when ambient relative humidity exceeds 50%. Moisture above 0.05% by mass hydrolyzes the polyester soft segment in the melt, reducing molecular weight and creating steam porosity at the nozzle. The resulting printed coupons fail prematurely under ISO 527-2 tensile loading, particularly in interlayer zones. A dry-air storage cabinet maintained below 15% relative humidity is preferable; regenerable silica gel or molecular sieve desiccant beds are acceptable if the cabinet is not opened for long periods. The filament should not be predried in a conventional kitchen oven without forced air; local hot spots above 100°C can soften the filament on the spool and cause blocking.

Polyester TPU moisture uptake at 50% relative humidity and 23°C reaches equilibrium in approximately 24–48 h. Once moisture content exceeds 0.05%, the time required for drying at 80°C is 3–4 h; at 60°C the drying time doubles. A moisture balance analyzer or Karl Fischer coulometric titration based on ISO 15512 is appropriate for quantitative verification. Spools should be placed vertically and not stacked during drying to avoid localized deformation of the outer windings.

The most common feed-path failure in contract printing is buckling in a long Bowden tube. If a Bowden extruder must be used, print speed should be reduced to 15 mm/s, retraction should be disabled or set below 1.0 mm, and the tube should be replaced with a low-friction PTFE liner. Direct drive is strongly preferred because the filament has low column strength. Batch-to-batch variation in diameter outside ±0.05 mm also causes measurable feed-pressure fluctuations; dual-axis laser micrometer checks are recommended before production runs.

The table below lists representative property ranges for initial process qualification. The values are not batch acceptance limits; lot-specific conformity should be verified against current Huntsman documentation.

The property values above are more reliably measured on printed plaques than on injection-moulded plaques, because layer interfaces contribute measurable anisotropy. Test coupons printed flat, with 0.10 mm layer height and 100% rectilinear infill, are preferred for comparing lots. Z-direction tensile strength is commonly lower than x-y tensile strength in filament-based elastomers; suppliers of TPU filament generally report that printed specimens show lower tensile elongation than datasheet values from injection-moulded specimens. This is a known limitation of fused filament fabrication and should be acknowledged in design.

If the Prototype Must Survive Oils, Abrasion, and Repeated Flexure

Protective cover prototypes, footwear midsole cores, low-pressure gaskets, and cable strain-relief geometries represent typical applications. These components are printed with continuous spiral or grid infill at 60–80% density to control deformation. In gasket verification, compression set testing based on ISO 815-1 should be used on printed discs rather than injection-moulded plaques because the layer interfaces alter the recovery behaviour. The tensile elongation of printed parts is typically lower than datasheet values from injection-moulded specimens; test coupons printed flat, with 0.10 mm layer height and no raft, are preferred for comparing lots. Published data for this specific configuration is limited; validation against the target industrial part is necessary.

Chemical resistance follows polyester TPU behaviour: the material resists diesel, mineral oil, and aliphatic hydrocarbon contact better than polyether TPU of equal Shore hardness. Ketones, chlorinated solvents, and strongly alkaline solutions can soften the matrix. Continuous exposure to hot water above 60°C is not recommended because the polyester backbone will hydrolyze, reducing tensile strength and elongation. When the printed part must meet flammability or skin-contact requirements, the relevant EU REACH and food-contact statements must be verified from current supplier documentation; the filament is sold for industrial prototyping, not as a medical-grade or implantable material.

Relative to polyether TPU filaments, Iroprint F 80112 polyester chemistry increases tensile modulus and abrasion resistance but lowers hydrolysis resistance. In comparative testing according to ISO 4649, polyester TPU grades generally show lower abrasion mass loss than polyether TPU of equal Shore hardness; the trade-off appears under saturated humidity or hot-water exposure, where polyester soft segments undergo faster chain scission. Against PLA and PETG, F 80112 exhibits lower tensile modulus and higher elongation; ABS and PLA prototypes behave as stiff thermoplastics, whereas F 80112 behaves as an elastomer that returns to shape after repeated deformation. Against thermoplastic copolyester filaments, F 80112 generally offers higher abrasive wear resistance but lower continuous service temperature. These distinctions are material-class characteristics, not substitute specifications.

For Build-Surface Selection and First-Layer Deposition

On a production-scale open-frame FFF machine, flexible TPU may detach from untreated glass if the first layer is too fast or the nozzle gap is too large. Use of a polyimide film, polypropylene bed, or polyurethane-based adhesive increases the separation energy. For a 0.4 mm nozzle and 0.10 mm first-layer height, a first-layer speed of 10–15 mm/s is reserved. Fan cooling is usually set to 30–50%; full cooling is not required for large flat parts and may induce curl in sharp corners. Retraction distance is kept below 2.0 mm at 20 mm/s; higher retraction pulls air into the nozzle and can create intermittent extrusion. These conditions are derived from flexible TPU processing practice and are adjusted when the filament is run in Bowden systems, though direct drive is preferred because the filament has low column strength.

The table below summarizes process parameter limits and associated failure modes observed in field operation.

Lot acceptance should include melt flow determination by ISO 1133-1 and Shore hardness by ISO 7619-1 on printed plaques to track batch-to-batch variation. Supports are removed manually; polyester TPU resists many solvent smoothing processes, so mechanical trimming is preferred. Cutting with a sharp blade at room temperature is more effective than cryogenic fracture. Published data for this specific configuration is limited; validation against the target industrial part is necessary.