| HS Code | 775161 |
| Color | Black |
| Hardness | 65 Shore D |
| Tensile Strength | 30 MPa |
| Tensile Modulus | 1,500 MPa |
| Elongation At Break | 20% |
| Flexural Strength | 45 MPa |
| Flexural Modulus | 1,300 MPa |
| Izod Impact Strength Notched | 50 J/m |
| Density | 1.15 g/cm³ |
| Heat Deflection Temperature At 0 45 Mpa | 55°C |
| Heat Deflection Temperature At 1 82 Mpa | 45°C |
| Water Absorption | 0.3% |
As an accredited 3D Systems VisiJet RBK-ENT-D65 Multi-Material Composites (VisiJet CR-BK + VisiJet CE-NT factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
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In HVAC duct joint prototyping for passenger car instrument panels, the composite designated RBK-ENT-D65 is separated into a rigid CR-BK flange and a CE-NT perimeter sealing bead. The flange is printed with snap hooks and locating ribs, while the CE-NT bead is dimensioned to operate at 18–22% compression in the installed stack height against an injection-moulded ABS or PP mating surface. Compression set is evaluated according to ASTM D395 Method B after 22 h at 70±2°C; a recorded set above 35% is treated as a reject limit for warm cabin air sealing because residual sealing force becomes insufficient on low-closure-force clips. The snap hook retention must be checked separately on the CR-BK material by flexural testing according to ASTM D790 using a 16:1 span-to-depth ratio, because Z-axis printed snap hooks can exhibit premature failure at interlayer boundaries. The combined part is washed in isopropyl alcohol and post-cured in a UV chamber; incomplete post-cure leaves residual acrylate functionality in CE-NT and causes compression set drift during cabin thermal cycling. For instrument panel components exposed to solar soak, accelerated aging according to ISO 188 at 90°C for 168 h should be performed before release, because the CE-NT elastomer is not assumed to be long-term stable above 70°C without lot-specific validation. The design boundary for this application is therefore a sealing bead, not a structural bond: CR-BK provides the retention geometry and CE-NT provides the low-force air seal.
The failure mode most frequently observed on multi-material handheld enclosure prototypes is not bulk elastomer rupture but a peel line at the CR-BK/CE-NT transition after repeated drop impact. Portable electronics housings use CR-BK for latch bosses, snap-fit retention ribs, and battery compartment walls, while CE-NT is overmoulded as a 65 Shore A soft-touch outer layer. Drop testing is commonly performed according to IEC 60068-2-31 from a height of 1 m onto concrete tile; the CE-NT outer layer functions as impact attenuation only if the overmould thickness is maintained above 1.0 mm, because thinner sections show substrate shadowing and locally increased hardness due to UV exposure gradients in the build envelope. Peel adhesion at the multi-material transition is evaluated by a 90° peel fixture based on ASTM D6862, using a 25 mm wide specimen pulled at 50 mm/min. A peel strength below 1 N/mm is generally rejected for snap-fit consumer covers because the CE-NT layer separates from the CR-BK substrate during corner impact. Print orientation is a critical variable: jetted elastomer voxels develop anisotropic crosslink density, so the peel line in the X-Y build plane differs from the peel line across Z-axis layer boundaries. Published data for this specific orientation-dependent interface is limited; therefore, a build-direction control coupon must be included in each lot. The housing is conditioned for 48 h at 23°C and 50% RH before testing according to ISO 291. A production-scale failure observed on actual print runs is CE-NT delamination from CR-BK when the overmould edge terminates without a mechanical interlock; a 0.5 mm recessed lip in the CR-BK substrate increases peel resistance and should be incorporated into the CAD model before printing.
For engine bay wire harness strain relief builds, the CR-BK shell is printed as a split cable gland and the CE-NT component is printed as a conical strain relief sleeve extending from the gland exit. The sleeve inner diameter is designed with 18–22% radial interference to the jacketed cable, a range selected to retain the cable under an axial pull force of 50 N commonly referenced in harness assembly specifications. Tear resistance of the CE-NT sleeve is measured by ASTM D624 die C; if the tear value after 168 h at 100°C is below the design margin, the RBK-ENT-D65 pair is not acceptable for high-temperature engine-bay service near exhaust or turbocharger heat sources. Fluid compatibility is not assumed: CE-NT may swell in engine degreasers, power steering fluid, or hot ethylene glycol mixtures. Immersion screening per ASTM D471 in IRM 903 oil and 50% ethylene glycol/water at 70°C for 168 h is required for each harness environment. The rigid CR-BK gland body must maintain thread engagement into the sheet-metal bracket; axial pull-out is influenced by the printed thread root geometry and should be checked against the bracket slot tolerance. The main processing bottleneck is support removal from the conical sleeve bore: incomplete wax support removal leaves a tacky residue that alters the cable interference ratio, so a borescope inspection after post-cure is recommended for small-diameter openings below 8 mm.
When compressed-air manifolds are printed as a single RBK-ENT-D65 part, the CR-BK body provides rigid port threads and internal flow channels while the CE-NT face seal provides low-torque closure against an aluminium or polyamide countersurface. The face seal is configured in a dovetail groove with a nominal compression of 25%, but the supplier datasheet does not list compression set for this exact groove configuration; a design verification coupon must be printed in the same build orientation and post-cured with the production lot. Gland dimensions are referenced to ISO 3601-1 static O-ring groove practice, though the lower modulus of CE-NT compared with moulded NBR or FKM means that gland fill should remain below 85% to avoid stress relaxation and surface cracking. The manifold is leak tested by pressure decay at 0.6 MPa compressed air for 300 s; a decay above 0.5 kPa is classified as a reject condition for downstream pilot tooling. The CR-BK port threads are not intended for repeated assembly above 5 cycles, because photopolymer thread wear can generate microchips that deposit on the CE-NT sealing face and initiate leak paths. A 40 µm filtration grade on the test air supply is used to prevent particulate embedding. The limiting compatibility concern for CE-NT in this application is exposure to compressor oil mist; if oil aerosols are present, the seal surface should be inspected by ASTM D471 immersion screening before system release. Published long-term sealing performance data for CE-NT under continuous 0.6 MPa air pressure is limited, so the design should be restricted to prototype and short-run functional validation rather than production pneumatic service.
| Application segment | Standard or method | Test parameter | Design boundary for RBK-ENT-D65 |
|---|---|---|---|
| HVAC duct sealing bead | ASTM D395 Method B | 22 h at 70±2°C | Compression set above 35% rejected |
| Handheld device overmould | IEC 60068-2-31 / ASTM D6862 | 1 m drop; 90° peel at 50 mm/min | CE-NT layer thickness 1.0 mm minimum; peel below 1 N/mm rejected |
| Engine bay strain relief | ASTM D624 die C / ASTM D471 | Tear after 168 h at 100°C; fluid immersion | Sleeve interference 18–22%; chemical swelling requires lot-specific screening |
| Pneumatic manifold face seal | ISO 3601-1 / pressure decay | 0.6 MPa air, 300 s | Gland fill below 85%; decay above 0.5 kPa rejected |
Benchtop liquid handling stations and diagnostic instrument housings use CR-BK as a structural chassis and CE-NT as a soft handle overmould for operators handling heavy modules during service access. The application is explicitly non-patient-contiguous; no skin-contact biocompatibility claim is made because the supplier datasheet for CE-NT does not establish mucosal, dermal, or implantable contact status under ISO 10993-1. If a design is reclassified for patient contact, ISO 10993-5 and ISO 10993-10 testing is mandatory on the finished printed part, including post-cured and cleaned surfaces. For laboratory instrument housings, mechanical enclosure testing according to IEC 61010-1 requires a 20 N steady force applied to the handle without cracked CR-BK ribs or CE-NT debonding. Cleaning validation is a major process risk: repeated wiping with 70% isopropanol can induce surface crazing or softening in CE-NT, and oxidising disinfectants such as 0.5% sodium hypochlorite can degrade elastomer elongation. Chemical resistance screening is performed by ASTM D543 immersion or swab cycling; a practical acceptance criterion is no visible surface cracks after 10 cleaning cycles under a 10× stereo microscope. The CR-BK chassis must not transmit screw-torque load through the CE-NT grip, because lateral stress at the material transition can create a hairline separation that accumulates biological soiling in laboratory service. The production printing constraint is that the overmould section must be oriented to avoid trapped support material in the grip undercuts; trapped wax residue can cause localized stain and is removed with a solvent flush followed by 48 h drying at 23°C.
In lightweight collaborative robot gripper builds, the CR-BK material is used for the vacuum channel adapter plate and the CE-NT material is used as the soft contact pad on the gripper jaw. The CE-NT pad at 65 Shore A conforms to surface asperities up to approximately 0.5 mm at a gripping pressure of 50 kPa; this value is a starting point for contact pressure mapping and must be validated with pressure-sensitive film on the actual target surface, because surface roughness and part curvature alter the conformal contact area. Coefficient of friction against borosilicate glass and corrugated board is measured according to ASTM D1894; published friction values for CE-NT are limited, so an internal fixture test with a 100 mm/min sliding speed and 1 N normal load is used to generate application-specific data. The CR-BK adapter plate is mounted to the robot end effector by M4 or M5 machine screws; printed holes are undersized and then reamed to final diameter to avoid thread splitting during assembly. The limiting operational boundary is shear loading at the CR-BK/CE-NT interface during part withdrawal: a 90° peel test based on ASTM D6862 should be performed on the co-printed bond line, because cohesive failure in CE-NT is acceptable while interfacial failure at the CR-BK boundary is not. The gripper pad must be inspected after each 100 pick-and-place cycles for tearing, edge chipping, and loss of Shore A hardness caused by process fluid exposure. No claim is made for food-contact gripping or cleanroom particle transfer without additional lot-specific testing under the relevant end-user standard.
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MultiJet Printing (MJP) of UV-curable resins in a single build cycle is the processing foundation for the material configuration identified as 3D Systems VisiJet RBK-ENT-D65 Multi-Material Composites. The configuration combines VisiJet CR-BK, a rigid black photopolymer, and VisiJet CE-NT, an elastomeric natural photopolymer, in a part-level distribution rather than a compounded polymer blend. The commercial designation can be decomposed as RBK for rigid black, ENT for elastomeric natural, and D65 for the Shore A 65 durometer of the elastomeric phase under ASTM D2240. The combination is intended for functional prototypes and short-run parts in which rigid structure and elastomeric compliance must coexist without adhesive bonding or mechanical fastening. Because the two photopolymers remain compositionally distinct during printing and cure, mechanical interdiffusion at the phase boundary is limited; the interface is a critical design variable when loads are applied across material transitions.
VisiJet CR-BK functions as the load-bearing phase. It is deposited from one material channel of a multi-material MJP platform, typically the 3D Systems ProJet MJP 5500X, while VisiJet CE-NT is jetted from the elastomer channel. 3D Sprint software interprets multi-body CAD data or mesh selections and assigns CR-BK or CE-NT regions according to shell thickness, overmolding masks, or discrete part geometry. The part is built at a layer thickness of 32 µm in standard mode; resolution within the build plane is controlled by the MJP printhead and planarizer. The D65 designation applies to the CE-NT phase durometer, not to the global part hardness. A completely rigid CR-BK portion of the same print remains a rigid photopolymer, while the elastomeric portion remains Shore A 65 under ASTM D2240. This phase contrast is the principal difference from single-resin VisiJet products.
On a multi-material MJP platform, material temperature, jetting waveform, UV cure dose, and chamber environment are controlled. The wet resin film is planarized after each layer and then exposed to UV radiation; the sequence repeats for both deposited phases. Because CR-BK and CE-NT differ in viscosity, surface tension, and cure kinetics, printhead temperature settings and planarizer speed must remain within the equipment manufacturer’s allowable window. Deviation from that window can produce jet dropout, short shots, or interfacial porosity. A sacrificial wax-like support material is deposited alongside the model. After the build, support is removed by thermal melt-out in a controlled oven. Published thermal removal procedures for the composite recommend ramp rates and hold temperatures that avoid distortion of the elastomeric phase; the rigid phase is also constrained by its heat deflection behavior under ASTM D648 at 0.455 MPa. Excessive oven hold time can weaken thin elastomer walls and degrade the rigid-elastomer interface.
For static sealing, a Shore A 65 elastomer is generally expected to conform to irregular mating surfaces under low closure force. In the RBK-ENT-D65 system, that conformance is obtainable, but performance must be confirmed by compression-set testing under ASTM D395 Method B. Photopolymer elastomers can exhibit higher permanent set than heat-cured rubbers after thermal aging; published data for this specific configuration is limited, so users should generate comparative data against the intended production elastomer. For dynamic sealing, the surface of CE-NT is not a filled rubber with internal lubrication or PTFE modification; friction must be measured under ASTM D1894 or a component-level drag test. Thin elastomer sections below 1.0 mm may show orientation-dependent tear resistance. Tear evaluation according to ASTM D624 should be performed on both z-oriented and x-y-oriented specimens to establish workable wall thickness. The rigid black CR-BK phase provides compression-load distribution and prevents gross extrusion of the elastomer when retained within a groove. A seal groove can therefore be printed as a CR-BK retainer with a CE-NT sealing bead, eliminating adhesive assembly.
Chemical resistance is a defined boundary for this photopolymer system. Immersion in aromatic hydrocarbons, ketones, chlorinated solvents, or strong alkaline cleaners can swell or microcrack the CE-NT phase; compatibility should be screened by mass and volume change after 24 h immersion under ASTM D543. The CR-BK phase may show less sensitivity to aqueous acids and alkalis, but the elastomeric phase usually controls the overall chemical limit. Long-term thermal aging of the composite should be evaluated under ASTM D573 at the application-specific temperature. Continuous load-bearing exposure above the published heat deflection temperature of the CR-BK phase is not recommended. Ultraviolet and visible light can cause color shift and surface embrittlement in the photopolymer network. If UV exposure is required, coatings or stabilizers must be qualified separately because post-applied coatings can alter the Shore A 65 surface response and interfacial adhesion.
Interfacial quality at CR-BK/CE-NT transitions depends on layer thickness, jetting sequence, UV dose, and part orientation. In a 32 µm layer build, the transition zone is typically narrow unless deliberate blending is programmed. Shear evaluation on notched composite coupons can be performed under ASTM D3167 for lap-shear configurations or ASTM D6862 for 90° peel when sheet-like features are produced. The failure mode must be classified as adhesive failure at the interface or cohesive failure within the CE-NT phase; cohesive failure indicates that the interface is stronger than the elastomer. Batch-to-batch durometer of CE-NT should be checked with a calibrated durometer under ASTM D2240 using a specimen thickness of at least 6.0 mm. Thinner specimens can produce false Shore A readings because of rigid backing effects. Liquid resin must be stored at recommended room-temperature conditions and protected from sunlight. Resin that has been left open may gain viscosity and cause printhead dropout. The manufacturer’s cartridge shelf life and handling instructions should be applied.
A comparison with single-material rigid VisiJet CR-BK or elastomeric VisiJet CE-NT defines the position of RBK-ENT-D65. In a monolithic CR-BK print, the entire part maintains the modulus and thermal deflection of the rigid photopolymer; there is no strain-relief region. In a monolithic CE-NT print, the article is compliant throughout and may not retain fasteners or hold position under structural load. RBK-ENT-D65 places the stiff phase only where required and the elastomer only where compliance is needed. Compared with two-shot injection molding, the composite removes mold fabrication and permits part-level Shore A 65 feature changes within a single design iteration; the limiting factors are MJP build speed and the thermomechanical properties of photopolymers. Compared with fused filament fabrication of rigid and flexible filaments, the MJP process provides smoother sidewalls and a 32 µm layer thickness but requires thermal support removal and controlled waste handling. No adhesive, primer, or mechanical interlock is necessary to join the phases, but the interface must be designed to avoid peel-dominant loading.
Acceptance testing for RBK-ENT-D65 should be organized around the following standards and equipment. The matrix does not replace the current 3D Systems datasheet but identifies the minimum verification set for technical comparison.
| Material attribute | Test method or standard | Typical target | Observations for RBK-ENT-D65 |
|---|---|---|---|
| Elastomeric phase durometer | ASTM D2240-15 | Shore A 65 | Measure on 6.0 mm minimum thickness; thin sections report erroneously high values. |
| Rigid phase tensile and flexural properties | ASTM D638-14, ASTM D790 | Published CR-BK datasheet values | Report z-axis results separately; photopolymer properties are orientation-dependent. |
| Elastomer tensile and elongation | ASTM D412-16 | Published CE-NT datasheet values | Use Die C; report both x-y and z orientation. |
| Compression set | ASTM D395-16 Method B | Application-specific % set | Photopolymer elastomers may show higher set than molded rubbers. |
| Tear strength | ASTM D624-19 | Report kN/m | Strongly dependent on print orientation and part thickness. |
| Heat deflection of rigid phase | ASTM D648-18 | Current CR-BK published value at 0.455 MPa | Do not exceed during support removal or load-bearing service. |
| Chemical resistance | ASTM D543-20 | Mass/volume change after immersion | Screen against ketones, aromatics, chlorinated solvents, and alkalis. |
| Interfacial adhesion | ASTM D3167 or ASTM D6862 | Report failure mode | Cohesive failure inside CE-NT is preferred over interfacial separation. |
| Color stability | ASTM D2244-21 | Report ΔE after defined UV exposure | Both rigid black and elastomeric natural surfaces may shift. |
Material batches should be conditioned for 24 h at 23 °C and 50 % relative humidity before destructive testing because photopolymer properties respond to temperature and moisture. When translating RBK-ENT-D65 data into a production specification, the design owner must verify the phase fraction, transition location, and build orientation on the coordinates of the actual MJP build tray. If a reliable upper service temperature for the composite is required, thermal aging data should be generated; otherwise, the lower of the CR-BK heat deflection temperature and the CE-NT continuous-use temperature recommended by the manufacturer applies. The material is not a replacement for high-elongation thermoset rubbers, high-impact engineering thermoplastics, or high-temperature rigid resins; its function is limited to applications within the thermomechanical envelope of UV-cured MJP photopolymers.
