| HS Code | 448264 |
| Hardness Shore A | 70 |
| Tensile Strength | 6.5 MPa |
| Elongation At Break | 250% |
| Tear Strength | 25 kN/m |
| Compression Set | 25% |
| Resilience | 45% |
| Density | 1.08 g/cm³ |
| Viscosity | 1,200 cP at 25°C |
| Cure Wavelength | 385-405 nm |
| Color | Translucent amber |
| Tensile Modulus | 4.0 MPa |
| Glass Transition Temperature | -35°C |
| Service Temperature Range | -40 to 120°C |
As an accredited Adaptive3D Elastic ToughRubber™ 70 (ETR 70) Elastomer for DLP factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | ETR 70 is supplied in a 1 kg opaque, light-resistant plastic bottle with a sealed cap and safety labeling. |
| Container Loading (20′ FCL) | 20′ FCL loading: Adaptive3D Elastic ToughRubber™ 70 (ETR 70) DLP elastomer in sealed, palletized drums; strapped, moisture-protected, labeled, and evenly loaded. |
| Shipping | Adaptive3D Elastic ToughRubber™ 70 (ETR 70) Elastomer for DLP is not classified as dangerous goods for transport by DOT, IATA, IMDG, or ADR. UN number, proper shipping name, hazard class, and packing group are not applicable. No environmental hazard. Ship in sealed, opaque containers; avoid heat, light, and freezing. |
| Storage | Store ETR 70 in its original, tightly sealed container, upright, in a cool, dry, dark, well-ventilated area away from sunlight, UV light, heat, sparks, flames, and oxidizers. Maintain 15–25 °C; avoid freezing or overheating. Reseal immediately after dispensing, use first-in/first-out, keep away from children/food, and follow the SDS. |
| Shelf Life | ETR 70 has a 12-month shelf life when stored unopened in a cool, dark, dry place at 15–25°C, protected from moisture. |
Adaptive3D Elastic ToughRubber™ 70 (ETR 70) DLP photopolymer is used in low-pressure fluid handling networks operating below 0.6 MPa (87 psi) to produce 1.5 mm to 3.0 mm full-face gaskets for aluminium manifold flanges when the sealing groove surface finish is controlled to Ra 0.8–1.6 µm. The resin is processed as a single-part 100% solids formulation; no solvent dilution or curative ratio adjustment is performed before printing. The only mixing-related variable is daily reconditioning of the vat resin by a low-shear rotary stirrer, because layer-to-layer reactivity drifts when settled resin is left without recirculation for periods longer than 8 h. Build parameters on a 385 nm DLP platform are held at 25–50 µm layer thickness, with exposure energy measured at the resin plane by a calibrated radiometer, typically in the range of 8–15 mJ/cm² per layer depending on projector homogeneity. Vat temperature is maintained at 28–32°C; temperatures above 35°C increase radical generation and reduce green-part feature fidelity. Green parts are washed in 2-propanol for 5–10 min, dried under forced air at 25–35°C, and post-cured in a 365–405 nm LED flood chamber for 30–60 min to shift the conversion of residual acrylate groups. Oxygen inhibition at the seal surface must be controlled because residual tack causes groove stiction and compromises pressure decay. Post-curing in a nitrogen-purged chamber or using a secondary flood exposure reduces surface oxygen inhibition, but overexposure beyond 60 min raises crosslink density and reduces elongation. Compression-set behaviour is assessed by ASTM D395-16e1 Method B after 22 h at 70°C; tear resistance is determined by ASTM D624-00 die C. Sealing performance is validated by a 24 h pressure-decay test with loss greater than 0.05% of test pressure indicating groove fill or surface porosity. ETR 70 seals are limited in mineral-oil circuits above 70°C because of progressive swelling; the resin is not a direct substitute for FKM or HNBR in hot hydrocarbon service. Terminal parts include hydraulic manifold access covers, pump face O-ring adapters, inspection port gaskets, and custom formed-in-place replacement seals for short-run OEM service.
When the design shifts from static sealing to cyclic positive-pressure actuation, the limiting parameter becomes anisotropic tear propagation along the Z-axis interlayer boundary. A 25–50 µm layer thickness is retained, but the exposure energy must be lowered toward the 8–10 mJ/cm² end of the window to preserve elongation at break; overcure above 15 mJ/cm² stiffens thin walls and reduces the strain required to initiate notch growth. Bellows walls are designed at 1.2–2.5 mm thickness, with internal air passages no smaller than 3.0 mm in diameter and drainage holes no smaller than 1.5 mm diameter to permit uncured resin evacuation before post-processing. Orientation of the bellow axis at 15–30° from vertical reduces stair-step stress risers on convolution roots; vertical printing of the same geometry produces higher dimensional accuracy but lower interlayer fatigue resistance. Internal channel surfaces are washed by flushing 2-propanol through the part at low pressure, followed by a dry-air purge at 0.05–0.10 MPa to remove residual solvent. After washing and 60 min post-cure at 25°C, air leak integrity is measured using a pressure-decay test at 20 kPa over 60 s; a drop greater than 0.1 kPa indicates pinhole defects at layer interfaces. Material performance is tested according to ASTM D412-16 using die C dumbbells, with Z-direction specimens cut from printed panels to quantify anisotropy. Cyclic pneumatic fatigue is performed by pressurizing a 50 mm stroke bellow at 0.05–0.15 MPa for 10,000 cycles; failure modes observed on production-scale builds are typically radial splits at the convolution root rather than bulk rupture. For soft robotic gripper pads, the resin is printed into 3–5 mm thick compliant contact surfaces with a hardness of 70A after post-cure. The process conflict is that thicker sections retain heat during post-cure and may develop thermal softening gradients; therefore, post-cure intensity is reduced to 2–3 mW/cm² for parts with wall thickness above 5 mm. Printed actuators are not rated for continuous operation with ester-based lubricants or strong alkaline cleaners because ester swelling softens the network. Terminal parts include pneumatic sorting bellows, soft robotic fingertips for material handling, and low-pressure air distribution connectors.
Vibration isolation mounts for laser interferometer tables and compact optical benches are printed with ETR 70 as 4–12 mm thick cylindrical or square dampers with integrable internal air cells. The compliance path is defined by dynamic stiffness rather than static hardness; ASTM D5992-96(2019) provides a methodology for dynamic mechanical properties using sinusoidal loading at frequencies from 0.1 Hz to 30 Hz, while ISO 10846-2:2008 addresses dynamic stiffness for resilient elements under static preload. A typical validation sequence applies a static preload of 10–30 N, then a 0.1 mm peak-to-peak sinusoidal displacement at 10–30 Hz, recording the loss angle δ. Printed dampers are post-cured for 30 min and then conditioned at 23°C and 50% relative humidity for 24 h before testing. The process ratio requiring control is the solid-to-air volume fraction in the lattice: air volume fractions of 0–15% increase damping but reduce load capacity; above 15% the part approaches buckling in the Z-axis. The loss factor is not controlled by a single resin property; it is determined by the interaction between the hyperelastic network and the entrapped air cells, so lattice topology is design-critical. Finite element analysis with a hyperelastic material model fitted to ASTM D412 uniaxial and ASTM D575 compression data is used to select wall thickness. Thick pigmented sections attenuate UV light, so cure depth may fall below 200 µm in highly pigmented lots; therefore, thick damper bodies are built in segmented sections or with internal light-transmission windows. The resin's relatively low thermal conductivity causes a shift in loss factor when part temperature exceeds 40°C; for optical breadboard isolators, continuous exposure to laser heat sources is limited to 40°C. Terminal parts include vibration isolation feet, kinematic mount cushions, and laser enclosure damping pads.
For short-run wearable assistive device pads and clinical strap cushions, ETR 70 requires a documented biocompatibility file because the printed part may contact intact skin for prolonged durations. ISO 10993-1:2018 requires a biological evaluation plan; ISO 10993-5:2009 is used for cytotoxicity screening, and ISO 10993-10:2021 for irritation and skin sensitization. Published data for this specific formulation under ISO 10993-10 is limited; therefore, each production lot intended for skin contact must be submitted to a certified laboratory for extraction testing. The processing sequence differs from industrial seals because the part is washed in a low-residue solvent, either 2-propanol or a tripropylene glycol monomethyl ether-based solvent, then post-cured in a nitrogen-purged UV chamber to reduce surface oxidation and extractable monomers. A wash time of 10–15 min is used for 3–5 mm thick parts, followed by a 60 min post-cure at 365–405 nm. Extractables testing is performed according to ISO 10993-12:2021 using accelerated solvents; the acceptance threshold is set by the intended skin-contact duration. The photoinitiator package and unreacted acrylate species may migrate into skin-contact substrates under heat and moisture, so extraction testing is mandatory before production release. The resin is not certified as USP Class VI, and no endotoxin claim is available from the manufacturer; therefore, fluid-contact or implant applications are outside the stated operational boundary. The part-format ratio is controlled by the thickness-to-span ratio of cushioning ribs: a rib height-to-base width ratio above 1.5 produces buckling under 20 N load, while a ratio below 0.8 loses conformance to the wrist or heel surface. Terminal parts include short-run orthotic pads, wearable sensor housings, and strap cushions for rehabilitation braces.
| Evaluation | Standard | Test condition | Typical acceptance criterion |
|---|---|---|---|
| Cytotoxicity | ISO 10993-5:2009 | MEM extract, 24–48 h | Grade ≤ 2 |
| Irritation | ISO 10993-10:2021 | Intracutaneous or patch | No persistent erythema or oedema |
| Skin sensitization | ISO 10993-10:2021 | Guinea pig maximization or LLNA | No sensitization response |
| Extractables | ISO 10993-12:2021 | Accelerated solvent extraction | Per risk assessment |
ETR 70 is printed as a flexible strain-relief sleeve over braided cable terminations for instrumentation connectors where repeated bending at the connector–cable junction causes jacket fatigue. The critical processing variable is sleeve wall thickness relative to cable diameter: for a 6–10 mm diameter cable, the strain-relief wall thickness is set to 1.5–2.5 mm, tapering to 0.8 mm at the free edge to avoid stress concentration. The printed sleeve is installed as a snap-fit or overmould substitute after solvent washing and 30 min post-cure. CAD-to-part compensation uses a negative offset of 0.15 mm on the inner diameter to achieve a light interference fit without excessive hoop stress. Flexural endurance is evaluated by a 90° bend test at 30 cycles per minute for 500,000 cycles under a 0.5 kg load; failure is defined as a visible crack deeper than 0.2 mm. The test is adapted from IEC 60068-2-27 shock and IEC 60068-2-6 vibration for connector accessories. The resin's tear resistance, measured by ASTM D624-00 die C, governs the splitting behaviour when the cable is subjected to lateral pull-out. Design rules include a minimum internal radius equal to 2 times the cable outer diameter to prevent compressive buckling of the sleeve. Stress relaxation under constant strain must be considered because clamping retention decreases when the part is held at temperatures above 60°C for more than 72 h. Thermal exposure is bounded by 80°C because the photopolymer network softens and loses clamping retention above that temperature. The material is not validated for high-voltage cable terminations above 1 kV; dielectric strength data for the printed state is limited. Terminal parts include strain-relief boots for data loggers, circular connector backshells, and cable gland adapters for laboratory instruments.
In footwear prototype sole construction, ETR 70 is printed as a 0.8–2.0 mm wall-thickness lattice core bonded to a solid outsole face to tune heel-strike energy absorption. The lattice design uses body-centred cubic or gyroid unit cells with strut diameters from 0.4–1.0 mm; the processing window is narrow because strut diameters below 0.4 mm tear during green-part handling, while diameters above 1.0 mm increase stiffness and reduce cushioning. Build orientation is set at 45° to the loading axis to avoid cleavage through the interlayer plane. Compression resistance is measured on a universal testing machine per ASTM D575-91(2018), with specimens preconditioned per ASTM D412-16. Rebound resilience is tested by ASTM D2632-15; the test result is influenced by post-cure duration because incomplete conversion lowers resilience. For working prototypes, soles are post-cured for 45 min at 365 nm, then conditioned for 24 h at 23°C and 50% relative humidity before mechanical testing. The resin's compression set after repeated heel loading is assessed by ASTM D395-16e1 Method B; accumulated set above 15% in heel-strike zones indicates cell densification and necessitates lattice redesign. Published data for this specific lattice configuration in ETR 70 is limited; therefore, each sole design is characterised by its own force-displacement curve rather than a universal modulus. The material is not a production midsole elastomer for athletic footwear due to abrasion resistance and cost constraints; it is limited to design validation, fit trials, and custom orthotic prototyping. Terminal parts include prototype running shoe midsoles, diabetic footbed inserts, and footwear production assembly fixtures.
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Adaptive3D Elastic ToughRubber™ 70 (ETR 70) is a single-component, solvent-free photopolymer elastomer formulated for digital light processing (DLP) vat photopolymerization in the 385–405 nm wavelength band. The product is supplied at a nominal post-cure hardness of 70 Shore A when measured with ASTM D2240-15 or ISO 48-4. ETR 70 is intended for elastomeric components requiring cyclic flexure, compressive recovery, and conformal contact: bellows, gaskets, seals, vibration isolators, and gripper jaws. The material is not a rigid DLP acrylate; its stress-strain response after full post-cure lies in the low-modulus, high-elongation region associated with rubbery networks, and its tear propagation resistance is higher than conventional flexible DLP acrylates according to supplier-published comparisons.
Interpretation of DLP elastomer data requires attention to build orientation and print parameters. Because photopolymerization proceeds layer by layer, the interlayer boundary contains a higher fraction of unreacted or partially reacted acrylate species than the in-plane polymerized regions. Tensile values obtained from flat-oriented Type C dogbones therefore differ from those obtained from vertical builds. Lot-specific certificates of analysis should be used for design; published data for this specific configuration is limited where indicated.
Conventional flexible DLP resins often achieve low hardness by using high concentrations of monofunctional urethane acrylate oligomers. The resulting networks may show high elongation but frequently lose tear strength and develop elevated compression set. ETR 70 is formulated as a higher-hardness member of the Adaptive3D Elastic ToughRubber series. Publicly available supplier comparisons indicate that its tear propagation resistance and compression set are closer to a thermoset elastomer than to a generic flexible acrylate photopolymer. Injection-molded thermoplastic polyurethane at 70 Shore A may retain higher ultimate tensile strength and elongation, but ETR 70 offers tooling-free production of complex DLP geometries with undercuts and variable wall thickness.
Table 1 summarizes representative post-cure data from supplier literature and pilot-line measurements. The ranges are not specification limits and should not replace lot-specific validation.
| Property | Test method | Reported range or typical value |
|---|---|---|
| Hardness | ASTM D2240-15 / ISO 48-4 | 68–72 Shore A |
| Ultimate tensile strength | ASTM D412-16 | 5.0–7.5 MPa |
| Elongation at break | ASTM D412-16 | 150–300% |
| Tensile stress at 100% elongation | ASTM D412-16 | 2.0–3.5 MPa |
| Tear strength | ASTM D624-00(2020), Die C | 18–32 kN/m |
| Compression set | ASTM D395-18 Method B, 22 h, 70 °C | 15–28% |
| Rebound resilience | ASTM D2632-15 | 20–35% |
| Density | ASTM D792-20 | 1.08–1.12 g/cm³ |
| Viscosity at 25 °C | ASTM D2196-20, Brookfield | 1,500–3,500 mPa·s |
The compression set data under ASTM D395-18 Method B are significant for sealing design. Many flexible DLP resins report compression set above 40% after 22 h at 70 °C, while ETR 70 remains below 28% in the manufacturer’s published data. Rebound resilience measured by ASTM D2632-15 is lower than that of natural rubber and many EPDM compounds; the methacrylate network dissipates more energy during retraction because of higher crosslink density and pendant acrylate species. This lower rebound should be included in dynamic seal and vibration-isolation calculations.
Table 2 places ETR 70 relative to broad commercial material classes. Values are assembled from public supplier literature and apply to typical grades, not to every specific compound.
| Material class | Tensile strength ASTM D412-16 | Elongation at break ASTM D412-16 | Tear strength ASTM D624-00(2020) Die C | Compression set ASTM D395-18 Method B |
|---|---|---|---|---|
| ETR 70 DLP elastomer | 5.0–7.5 MPa | 150–300% | 18–32 kN/m | 15–28% |
| Flexible DLP acrylate | 2–4 MPa | 30–90% | 5–15 kN/m | 40–80% |
| Compression-molded EPDM 70A | 8–15 MPa | 200–400% | 25–45 kN/m | 10–25% |
| Injection-molded TPU 70A | 20–35 MPa | 300–500% | 50–80 kN/m | 20–40% |
Table 2 illustrates that ETR 70 occupies a design space between flexible DLP acrylates and thermoset elastomers. The DLP network offers tooling-free complexity, but its tensile and tear properties do not match high-grade EPDM or TPU. The absence of tooling does not remove the requirement for post-cure, orientation-specific testing, and chemical compatibility validation.
On production DLP arrays, vat temperature and recoater settings dominate build reliability. ETR 70 viscosity at 25 °C is typically reported in the 1,500–3,500 mPa·s range, which is higher than most rigid resins and close to the upper limit for passive recoating on small-format printers. Heating the vat to 30–35 °C lowers recoating force and improves resin redistribution. A wiper or roller with a 200–400 µm gap is recommended on bottom-up machines with 405 nm LED arrays and fluoropolymer or PDMS release films. Layer thicknesses of 50 µm and 100 µm have been demonstrated; 100 µm layers reduce the number of interlayer boundaries and lower delamination risk, but they increase surface stair-stepping.
Oxygen inhibition at the vat interface lowers conversion on the newly printed surface. If exposure dose is insufficient, the surface remains tacky and tensile properties fall below flat-panel data. Process-development trials should use exposure matrices with increments of 20–40 mJ/cm² until tack disappears and the expected modulus is reached. At 385 nm, photoinitiator absorption is usually stronger, cure depth decreases for the same energy dose, and the process window narrows on large cross-sections. A full factorial design with at least three exposure levels and two build orientations is the minimum needed for reliable parameter transfer to a new DLP machine.
The photopolymer network is formed from aliphatic urethane acrylate oligomers and multifunctional acrylate diluents. This network differs from sulfur- or peroxide-crosslinked EPDM and from thermoplastic polyurethane segmental structures. Crosslink density is higher and molecular weight between crosslinks is lower; ETR 70 therefore shows higher stiffness at low elongation and lower ultimate elongation than high-performance thermoset elastomers. In pilot-line operation on a 405 nm bottom-up DLP platform, large cross-sections exceeding 50% of the build area required heated vats and reduced peel speed. Observed failure modes included corner delamination, vat-surface smear, and partial interlayer separation after post-cure. Z-axis shrinkage of 1–3% after post-cure was observed; this should be compensated in CAD geometry in the same way mold shrinkage is compensated in injection molding.
Sealing elements printed from ETR 70 have been evaluated in low-pressure, non-contact and lightly loaded face-seal geometries. Published data for this specific configuration is limited, but comparisons to EPDM are constrained by differences in network architecture. EPDM relies on sulfur or peroxide crosslinks between high-molecular-weight polyethylene-propylene chains; ETR 70 forms a methacrylate-rich network from lower-molecular-weight telechelic oligomers. The ETR 70 network therefore displays higher stiffness at low elongation and lower ultimate elongation than a typical 70 Shore A EPDM compound. Short-term compression set under ASTM D395-18 Method B at 70 °C can be below 28%, but oxidative aging and fluid exposure must be validated for each seal environment.
Resistance to mineral oil, glycol-water mixtures, and aqueous salt solutions is not equivalent to EPDM or TPU. The polar urethane and residual acrylate functionality in ETR 70 can increase swelling in polar solvents. For a seal exposed to 80 °C mineral oil, volume swell should be measured according to ASTM D471-16a for 70 h; if the volume change exceeds the dimensional tolerance of the gland, ETR 70 is not a suitable replacement. Compressive stress relaxation should be measured according to ISO 3384-1 under the intended service temperature. Bellow and diaphragm applications should place the highest cyclic strain in the print plane because the interlayer boundary has lower fracture resistance under tensile loading perpendicular to the layers.
Chemical compatibility of printed ETR 70 is not identical to molded elastomers. Immersion testing according to ASTM D471-16a should be performed with the intended fluid at service temperature. Polar solvents, ketones, esters, and chlorinated solvents are likely to cause swelling above 40%; published data for this specific configuration is limited. Water-glycol mixtures are less aggressive, but water absorption can reduce tensile strength by 10–20% after saturation. Continuous exposure to hot air above 120 °C should be avoided because oxidative degradation of the acrylate backbone reduces elongation and increases compression set.
Anisotropy in DLP elastomers is a constitutive property, not a cosmetic artifact. Flat-oriented Type C dogbones printed with 100 µm layers and 405 nm exposure often exhibit elongation at break in the upper part of the range shown in Table 1. Vertical dogbones can lose 30–50% of that elongation because the tensile axis crosses multiple interlayer boundaries. The difference is attributed to incomplete interlayer conversion, oxygen inhibition, and residual monomer migration kinetics in the polymer matrix. Before ETR 70 is used in a load-bearing design, tensile tests should be conducted on specimens printed in the same orientation as the intended part. A minimum set includes five flat and five vertical specimens conditioned at 23 ± 2 °C and 50 ± 5% RH for 24 h before testing under ASTM D412-16.
Post-cure modifies the interlayer boundary by driving residual acrylate conversion. A two-stage post-cure is commonly used: an initial UV stage at 385–405 nm with a total dose of 10–15 J/cm² per side, followed by a thermal soak at 60–80 °C for 2–4 h to complete dark-cure of residual acrylate species. The UV chamber should emit in the same wavelength range as the printer; broad-spectrum mercury lamps should be filtered to avoid excessive 254 nm shortwave radiation that can cause surface microcracking. Thermal soak above 80 °C may cause shape distortion if the part is not supported, because the glass transition temperature of the partially cured network is lower before complete conversion.
Vat maintenance and solvent cleaning affect final mechanical properties. After each print, the resin should be drained into a light-tight container and filtered through a 190 µm stainless-steel mesh to remove partially polymerized particles. Do not use acetone or ketone solvents for cleaning green parts unless the manufacturer explicitly approves them; ketones can extract unreacted oligomers and embrittle the surface. Isopropanol or a supplier-approved hydrocarbon solvent is preferred. Immersion time should not exceed 5 min per wash cycle, and parts should be air-dried before post-cure. Residual solvent trapped in the network can plasticize the elastomer and reduce Shore A hardness by 3–5 points after thermal aging.
The uncured ETR 70 resin is incompatible with strong nucleophiles, basic conditions, and amine-containing surface primers, which can initiate premature crosslinking or exothermic polymerization. It should be stored between 15 °C and 30 °C and protected from ultraviolet and visible violet light. If condensation forms in the vat, the resin should be filtered through a 5 µm mesh before printing; water contamination can alter polymerization kinetics and create surface porosity. A safety data sheet should be reviewed for specific hazard classifications. REACH and RoHS compliance statements should be obtained from the supplier for the specific lot; no independent certification is implied in this technical description.
Because the formulation uses aliphatic urethane acrylate oligomers, ETR 70 exhibits lower yellowing under UV than aromatic urethane acrylate resins. External exposure remains a concern; no long-term weathering data under ISO 4892-2 are published for ETR 70. Parts intended for outdoor use should be subjected to at least 500 h of accelerated weathering and then re-tested for tensile and tear properties. Surface gloss changes and microcracking can occur before bulk mechanical failure.
For gripper jaws requiring conformal contact but no continuous exposure to hot water above 60 °C or hydrocarbon oil, ETR 70 has been used as a direct replacement for cast polyurethane in batch sizes below 100 parts. Build orientation should place maximum tensile strain in the print plane. The production geometry should be validated with a 1000-cycle fatigue test because published fatigue data for ETR 70 DLP parts is limited. Batch-to-batch viscosity variation of ±10% requires re-tuning of exposure dose and recoater speed for each new resin lot. Failure to re-tune has resulted in delamination on large cross-sections and non-uniform cure depth in pilot production.
