Within the SLS polymer powder range of 3D Systems, DuraForm TPU Elastomer is an unfilled thermoplastic polyurethane powder formulated for CO₂ laser sintering platforms. The product is supplied in white powder form with machine-specific build profiles covering 3D Systems SLS systems. It is directed at rubber-like components requiring elastic recovery, low hardness, and high tensile elongation rather than rigid polyamide structural response. As a powder-bed material, the product does not require support structures, but part properties are strongly dependent on energy density, bed temperature, and the mass fraction of recovered powder. Storage before processing should keep the material below 30 °C and protected from moisture ingress; containers that have been opened should be resealed under dry conditions or consumed within a validated interval. The recommended powder bed preparation includes a controlled preheating step to reduce surface moisture, as absorbed water can form microvoids at the laser fusion front. Compared with stereolithography elastomers, the sintered TPU process enables construction of unsupported hollow channels and snap-fit undercuts. However, orientation-dependent interlayer fusion is an operational boundary. In production-scale builds on SLS systems, the Z-axis strength is typically below the X-Y-plane strength by 10% to 30% depending on layer thickness and scan strategy. For components with cyclic bending across the build plane, ASTM D638 Type IV specimens oriented in the Z-axis should be used to define conservative design allowables. Post-sinter annealing at 100 °C for 2 h can relieve powder-bed residual stress, but it does not convert the layer structure into a homogeneous elastomer network. Process settings must therefore be tuned for the specific platform; user-developed build profiles that exceed the energy input recommended by the material file can produce glossy surfaces, lower elongation, and part growth.

What Mechanical Property Values Are Reported for Sintered Test Coupons?

Representative data for DuraForm TPU Elastomer are summarised in the following table from manufacturer technical documentation. Values are generated on sintered tensile coupons; they should not be interpreted as design minimums. Lot-to-lot variation and powder reuse ratio can shift the following data by 10% to 25%, particularly for elongation at break and tear strength.

Property	Test standard	Reported value
Hardness	ASTM D2240	65 Shore A
Tensile strength at break	ASTM D638-14 Type IV	6.0 MPa
Elongation at break	ASTM D638-14 Type IV	300%
Tear strength	ASTM D624-00 Die C	30 kN/m
Density	ASTM D792	1.08 g/cm³
Compression set	ASTM D395-03 Method B	15% after 22 h/23 °C

The Shore A hardness of 65 places this material in the soft elastomer class, overlapping with extruded TPU 65A filaments but obtained without a layer extrusion path. The tensile elongation at break above 300% is a key selection criterion for bellows and living-hinge covers. Tear strength measured by ASTM D624 Die C is used for assessing resistance to crack propagation at mounting holes and overmoulded features. Because the material is porous after sintering, measured density remains near 1.08 g/cm³; post-process infiltration can increase density and alter stiffness. The compression set behaviour after 22 h at 23 °C is low enough for static seals, but elevated-temperature compression set requires separate testing. Users should obtain batch certificates for the specific machine and build orientation. On 3D Systems SLS platforms, the TPU Elastomer build file controls the powder bed preheat, laser scan strategy, and part-bed offset. These are distinct from DuraForm PA Plastic build files. A build profile for a rigid PA12 powder must not be substituted because the lower melting onset of the TPU leads to over-sintering, fusion of surrounding powder, and loss of fine features. Operators working with production-scale sPro and ProX systems have noted that electrostatically charged powder can adhere to the recoater blade when the room dew point is below −10 °C; this condition produces streaks and uneven layer density. Conversely, high relative humidity above 60% reduces electrostatic effects but increases powder moisture. The powder feed and build chamber should therefore be maintained within a stabilised range; the exact values vary with plant HVAC and should be logged continuously. Long production runs with recycled powder introduce a property-retention issue that is more severe in TPU than in rigid nylon SLS materials. The urethane hard segments can undergo thermo-oxidative chain scission during repeated bed heating cycles; antioxidant depletion is indicated by yellowing, reduced elongation, and a narrowing of the energy window. A production-scale validation campaign should build ASTM D638 Type IV coupons at virgin-reclaimed blend fractions of 0, 30%, 50%, and 70% recovered powder. Published data for this specific configuration is limited, but the general failure pattern is a rapid drop in elongation above 50% recovered fraction in high-humidity, high-bed-temperature environments. The safe processing boundary therefore depends on the critical retained elongation required by the part. When parts are annealed or dyed after sintering, the thermal history may further drive hard-block ordering; validation should include the full post-processing sequence rather than green-state coupons. Moisture uptake is an operational constraint. At relative humidity above 60%, powder left in the feed hopper can pick up sufficient water to produce intermittent part porosity and surface roughness. Pre-drying should follow the equipment manufacturer’s guidance; published data for this specific configuration is limited, and users should verify residual moisture by mass-loss analysis at 105 °C or with a halogen moisture balance. Drying must be performed below the softening point of the TPU powder to prevent agglomeration. A conservative dry-air drying temperature of 70 °C for 4 h is used for many TPU powders, but the specific grade should be verified. Powder that has been overheated can exhibit fused clusters that block recoat spreaders and produce streaks in the bed. Recycled TPU powder on long campaigns is affected by both thermal history and humidity. A production campaign that returns hot powder from the build chamber to the feed bed can retain heat and initiate oxidative degradation if not cooled below 50 °C before blending. The powder should be sieved to remove fused agglomerates; mesh sizes between 150 µm and 250 µm are common for SLS powder handling, but the specific product’s particle-size distribution is provided by the manufacturer. Retained tensile elongation after recycling is a better indicator of powder life than hardness; hardness can remain within 5 Shore A units while elongation degrades by 30%. Therefore, part certification tests should not rely on durometer alone.

When Environmental Exposure Limits the Use of Sintered TPU Parts

SLS polyurethane elastomers are generally unsuitable for continuous service in steam, hot water, strong acids, strong bases, or highly polar organic solvents. The ester or ether segments in the polyurethane backbone can hydrolyse at elevated temperature; immersion testing under ISO 1817 is required before specifying this material for gaskets or seals in contact with process fluids. Ketones, chlorinated solvents, and esters swell the matrix, while nonpolar lubricants may cause more gradual mass change. For dry cleanroom boots, cable grommets, and dust covers, the material is used within its chemical resistance limits. Because the sintered surface retains open porosity, sealing surfaces may require a post-process coating or infiltration when low leak rates are specified under ASTM F37 or ISO 22899 test protocols. Impact-protection and damping components use the elastomeric character of the TPU under dynamic deformation. Compression set at elevated temperature is a more critical predictor of service life than room-temperature hardness. Parts exposed continuously to 70 °C may show increased set; this should be measured under ASTM D395 Method B at the expected service temperature rather than the 23 °C standard condition. Cyclic flexing should be validated with ASTM D638 residual strain measurement after 50% strain cycling, or with a De Mattia flex test where crack initiation cycles are reported. The SLS process also produces an as-sintered surface roughness that can initiate cracks at high strain concentrations; tumbling or vibratory finishing can improve surface quality but may reduce fine feature definitions. The reported elongation above 300% is an engineering value, not an intrinsic limit. Strain rate and grip type influence the result; ASTM D638 Type IV specimens may exhibit break inside the gauge length at lower rates if stress concentrations are present. The reported value may be lower for parts with rough as-sintered surfaces; these are crack-initiation sites. For high-strain components, the finish should therefore be considered as part of the design allowables, or surfaces should be polished or coated before testing. Thermal stability under continuous service is bounded by the thermoplastic nature of the elastomer. Short-term exposure to 100 °C may soften the part and increase creep under load; long-term exposure above 70 °C in air can cause oxidation and surface embrittlement. Low-temperature flexibility is a function of the soft-segment glass transition; this is typically measured by differential scanning calorimetry according to ISO 11357-2. Parts used in cold environments should be impact-tested at the lowest service temperature because Shore A hardness rises as the soft segment approaches its glass transition. Against rigid DuraForm PA Plastic and glass-filled DuraForm GF Plastic, the TPU Elastomer is specified where tensile modulus and hardness must drop by orders of magnitude. Rigid SLS polyamide grades show tensile strength values above 40 MPa and elongation below 25%, whereas the TPU Elastomer presents Shore A 65 and tensile elongation above 300%. The trade-off is wear resistance and temperature capability: rigid polyamide parts can survive higher service temperatures and offer higher abrasion resistance in dry running conditions. Against DuraForm Flex, the TPU Elastomer is softer, with a durometer quoted in Shore A units rather than Shore D. DuraForm Flex is a semi-rigid material suited to thin snap-fit beams and clips; DuraForm TPU Elastomer is a rubber-like material for gaskets, ducts, impact covers, bellows, and soft-touch housings. In parts that must withstand repeated elastic deformation, the TPU Elastomer provides lower stiffness and higher elastic recovery. Compared with fused-filament TPU 95A grades, the SLS TPU Elastomer eliminates nozzle path anisotropy and the requirement for support removal, but it introduces powder-contact surface roughness and a more costly recycling discipline. Filament TPU parts can be produced with Shore A values near 95 and higher tensile strength; the sintered TPU Elastomer is purposely positioned at a lower hardness range for soft seals and protective covers. In laser-sintered form, the polymer network is built in a powder bed that allows free-standing helical bellows, complex manifolds, and nested parts. However, the powder remains lodged in internal cavities and requires compressed-air clearing or ultrasonic cleaning. Any post-process sealing with solvent-based coatings must be compatibility-tested to avoid swelling and surface tack. RoHS and REACH declarations are not equivalent to end-use regulatory clearances. The product can be screened against EU 2011/65/EU and Regulation (EC) No 1907/2006 SVHC lists, but no food-contact or medical-device certification is included in standard technical documentation. If parts are intended for wearable devices or orthotic pads, cytotoxicity and skin-contact testing under ISO 10993-5 and 10993-10 should be conducted on sintered coupons because powder residue and post-processing may alter the surface. Similarly, flammability classification is not automatically inherited from the raw powder; any application requiring UL 94 flame ratings must test the sintered geometry. These boundary conditions constrain the material’s use to industrial seals, ducting, protective covers, flexible housings, and functional elastomer prototypes where mechanical performance, not regulated body contact, is the primary acceptance criterion.