Eastman Amphora™ FL6000 Flexible 3D Polymer is a copolyester-based thermoplastic elastomer supplied for fused filament fabrication and pellet-fed material extrusion. The product code FL6000 designates the flexible grade within the Amphora 3D polymer portfolio; rigid products under the same portfolio include AM1800 and AM3300. Filament is converted by extrusion houses from neat pellets and is available in 1.75 mm and 2.85 mm diameters. Nominal diameter tolerance is usually held to ±0.05 mm when measured at 23°C and 50% relative humidity with an in-line laser micrometer. Published typical specific gravity is 1.04 by ASTM D792. Published typical hardness is Shore A 95 by ASTM D2240. Tensile elongation at break is reported above 500% by ASTM D638 Type IV at 50 mm/min; this value is for compression-molded or injection-molded specimens unless otherwise noted. These values differentiate FL6000 from rigid copolyester grades that typically exhibit tensile elongation below 10% and hardness in the Shore D range.

Mechanical data from printed parts are orientation-dependent. Tensile elongation and ultimate tensile strength decrease when tensile axes are perpendicular to layer interfaces; the reduction is attributed to incomplete interlayer chain diffusion and sporadic weld-line voids. Published data for FL6000 in the perpendicular build orientation are limited; therefore, printed test bars should be prepared under ISO 527-2:2012 with the intended layer height and infill pattern. Comparatively, rigid Amphora grades display higher tensile modulus but fail brittle at room temperature, whereas FL6000 maintains elastomeric recovery at room temperature but does not possess the high-temperature load-bearing stiffness of amorphous grades.

What separates this copolyester elastomer from rigid Amphora grades and TPU?

Unlike thermoplastic polyurethane, FL6000 is a copolyester thermoplastic elastomer and does not depend on phase-separated polyol and diisocyanate hard segments. This chemical difference removes isocyanate-related safety concerns during filament manufacturing and lowers moisture uptake relative to polyether TPU in some immersion environments; however, quantitative moisture diffusion coefficients are not publicly disclosed for FL6000. The polymer retains flexibility at room temperature without external plasticizer. In hydrolytic aging, copolyester systems can undergo acid-catalyzed chain scission at elevated temperature; immersion testing under ISO 1817 or ASTM D471 is required before replacing TPU in hot-water or acidic service.

Pre-drying is required before filament extrusion and before printing when spool storage has exceeded 4 hours at ambient relative humidity above 60%. Pellets are dried at 65°C for 4 hours in a desiccant dryer with a dew point of -40°C or lower. Filament spools are dried at 60–65°C for 4–6 hours. Residual moisture is verified by Karl Fischer titration and maintained below 0.04%. Feed-throat humidity should be maintained below 10% relative humidity on production lines. If moisture exceeds 0.04%, the melt exhibits steam bubble formation at the die exit, diameter variation, and reduced weld strength because polyester hydrolysis lowers molecular weight. Drying temperatures above 75°C should be avoided because prolonged exposure can cause pellet blocking at the feed throat.

Melt Rheology, Residence Time Limits, and Extrusion Hardware

The melt-flow index of FL6000 is approximately 4 g/10 min at 230°C under 2.16 kg load when measured by ISO 1133-1:2022 or ASTM D1238; published manufacturer data should be checked for the specific production lot. The material is pseudoplastic, with viscosity decreasing under high shear. Capillary rheometry data at shear rates from 100 s⁻¹ to 1,000 s⁻¹ are needed for nozzle-flow modeling because melt-flow index is not a direct predictor of print performance. The melt-temperature window is narrow: below 210°C, melt viscosity is high and die swell increases; above 250°C, oxidative degradation reduces tensile elongation. Residence time in the hot barrel should not exceed 8 minutes. Thermal degradation products may become visible as yellowing and may generate die lip buildup on filament extruders.

In production filament extrusion, a single-screw extruder with L/D 24:1 to 30:1 and a compression ratio of 2.5:1 to 3.0:1 is used with a general-purpose screw and a 60/80/60 screen pack. Zone temperatures are set with a feed zone at 180–200°C, compression at 210–230°C, metering at 225–240°C, and die at 230–245°C. Melt pressure is kept below 120 bar to limit shear heating. The filament is quenched in a water bath at 40°C, and a closed-loop laser diameter control adjusts puller speed. Batch-to-batch differences in melt flow can change filament diameter by ±0.03 mm if tension and pressure are not dynamically controlled. The material should not be blended with high-amine additives; polyester aminolysis produces chain scission and reduces tensile elongation at break.

On a direct-drive fused filament machine with a 0.4 mm hardened nozzle, extrusion temperature is set between 220°C and 245°C. A bed temperature of 30–70°C is used depending on part size. Layer height may range from 0.10 mm to 0.25 mm; heights below 0.10 mm increase print time and do not improve interlaminar strength in most open-chamber machines. Print speed is kept at 20–40 mm/s. Higher speeds may lead to under-extrusion and weld-line splitting because the nozzle pressure drop increases. A direct-drive extruder is preferred over a Bowden tube because the elastomer deforms in long guide tubes. For large parts, a 0.6 mm nozzle reduces shear stress and print time, but a lower exterior-wall speed of 15–25 mm/s is recommended. A melt-temperature probe is required when print speeds or nozzle sizes are increased beyond these ranges to prevent shear heating above 250°C.

When the Build Chamber Is Heated above 60°C and Cooling Fans Are Disabled

Interlayer adhesion in FL6000 is limited by chain-end diffusion across the weld interface. If deposited melt temperature falls below 190°C, weld strength decreases because the interfacial diffusion time is shortened. Cooling fans are therefore disabled for the first 2 mm of Z height. A heated build chamber maintained at 60–70°C reduces warpage for envelopes larger than 100 mm × 100 mm; below 60°C, large thin sections lift from polyetherimide build sheets. Adhesion to polyvinylpyrrolidone-based glue stick and polyetherimide sheet is acceptable, but glass surfaces without adhesion promoter result in first-layer delamination during flexural loading. The build plate should not be removed for part extraction until bed temperature falls below 30°C to prevent elastic strain recovery from causing permanent deformation in thin walls. Flexural fatigue data for FL6000 printed parts are not fully specified in general product literature; testing per ASTM D7774 using the intended infill pattern is required for load-bearing fatigue analysis.

Chemical compatibility is evaluated by ISO 175 or ASTM D543. Dilute inorganic acids and alkalis show short-term splash resistance. Ketones, esters, chlorinated solvents, and aromatic hydrocarbons cause swelling and strength loss. Concentrated sulfuric acid and some phenolic compounds are incompatible. The polymer is not recommended for continuous immersion in hot water above 60°C because copolyester hydrolysis accelerates. Post-printing solvent polishing with methyl ethyl ketone is not recommended because the polymer can craze under residual stress. Mechanical finishing by end milling or cryogenic deflashing is possible. Published data for tear strength after finishing are limited; tear strength is evaluated by ASTM D624 using die C, but the exact value depends on print orientation and should be measured for each lot.

Regulatory Compliance and Safety Data Sheet Conditions

Safety data sheets identify the product as non-hazardous under Globally Harmonized System criteria. The polymer is RoHS recast compliant for lead, mercury, cadmium, hexavalent chromium, PBB and PBDE. REACH SVHC content is below the communication threshold of 0.1 wt%. The material is not certified to USP Class VI or FDA 21 CFR food-contact standards based on published documentation. Ultraviolet stability is limited; outdoor use requires testing per ASTM G154 accelerated weathering. Electrical surface resistivity is not specified in the manufacturer’s general datasheet; printed parts are not to be used for electrical insulation unless tested to IEC 62631-3-2.

Compression set is an important selection criterion for gasket and seal applications. Measurement is performed by ASTM D395 Method B at 23°C and, if required, 70°C for 22 hours. Published compression-set values for FL6000 printed parts are limited; injection-molded values may overstate recovery because printed parts contain microvoids at layer interfaces. Therefore, compression-set testing should be performed on printed specimens with the same infill density, wall count, and build orientation intended for service. Gasket flanges clamped with 0.5 MPa or higher seating stress may undergo stress relaxation; relaxation is measured by ISO 3384 and should be reported for the expected service temperature.

In orthotic and prosthetic prototyping, FL6000 is used for flexible hinges, padding interfaces, and dynamic orthoses where Shore hardness in the 90–95 range and high elongation permit repeated flexure during gait simulation. Validation follows ISO 22523:2006 for external limb prostheses and orthoses, but material-level fatigue data for FL6000 are limited; therefore, printed articles should be tested on a dynamic test rig at the intended flexion angle and number of cycles. The material may not replace pressure-distributing cushioning foams because its compression set and energy return differ from open-cell polyurethane foam.

In electrical housings, FL6000 is not an electrical insulator. Surface resistivity is not specified in the general datasheet; testing per IEC 62631-3-2 is required if the printed article is used in electrical enclosures. The polymer is not flame-retardant; no UL 94 V-0 classification is claimed unless a specific compounded grade is supplied.

Where do published data stop for high-rate printing?

Published mechanical property values for FL6000 are typically generated from injection-molded or compression-molded test plaques rather than printed parts. For build rates above 50 mm/s with a 0.6 mm or larger nozzle, published data are limited. High-output melt pumps may produce melt temperatures that exceed 250°C due to shear heating; therefore, an in-line melt-temperature probe is required before high-rate extrusion. Print geometry influences weld strength: vertical flat walls retain higher elongation than short zigzag paths with frequent starts and stops because residence time at the weld interface is longer. Published data for FL6000 in pellet-fed large-format machines are limited; the material should be characterized on the specific system with standardized test plaques per ISO 527-2:2012 before production release.

Because printed FL6000 parts are anisotropic, design stress must be reduced relative to isotropic material data. For tensile loading perpendicular to the layer plane, published data for this configuration is limited. End users should generate control data on the same printer, nozzle, filament batch, and chamber conditions used for production. The product datasheet values are not design allowables.