In fused filament fabrication cells where an unpigmented styrene-acrylonitrile-butadiene feedstock is preferred for post-print solvent bonding or precise color-critical overpainting, the Clariant Natural Color ABS 3D Printer Filament is specified as an unfilled terpolymer filament in 1.75 mm or 2.85 mm nominal round cross sections. The material is manufactured from an ABS matrix in which the butadiene-rubber phase is grafted to styrene-acrylonitrile copolymer; the natural designation indicates that inorganic or organic colorants are not intentionally added, producing a translucent to pale-cream extrudate. Published quantitative data for this specific Clariant configuration is limited; the processing windows and mechanical ranges presented in this document are consolidated from extrusion-grade ABS technical literature, ISO conditioned-specimen data, and production-scale fused deposition modeling observations. Where batch-specific verification is required, the supplier certificate of analysis should be consulted before implementing the parameter set.

What Is Being Characterized When the Pigment Package Is Absent?

The absence of titanium dioxide, carbon black, iron oxide, or organic colorants removes both a light-scattering phase and a potential nucleation surface. Under ISO 1043-1:2011 the material remains coded as ABS; under ISO 2580-1:2004 it would be classified as an unfilled styrene-acrylonitrile-butadiene moulding and extrusion material unless the supplier applies a specific designation. The natural appearance is not a measure of purity: residual stabilizers, lubricants, and processing aids may still be present. For regulatory documentation, material safety data sheets should confirm whether the grade satisfies REACH Article 33 communication obligations and RoHS 2011/65/EU Annex II restrictions. Natural color does not automatically imply food-contact compliance under FDA 21 CFR 177.1020 or EU 10/2011; end-use suitability must be evaluated against the final printed article.

Because the butadiene phase contributes melt elasticity and die swell, the extrusion and printing viscosity of natural ABS is more temperature-sensitive than that of unfilled PLA. Melt flow rate measured at 220 °C with a 10 kg load under ISO 1133-1:2022 typically falls between 5 and 20 g/10 min for unfilled ABS; unpigmented variants can show a slightly lower low-shear viscosity than identical matrices containing 2–5 wt% inorganic pigments because the pigment volume fraction is absent. At the nozzle, this translates to stable layer deposition between 220 °C and 250 °C, with the upper bound reserved for hardened steel or high-flow nozzles and the lower bound for slower volumetric throughput. For unfilled ABS grades, apparent viscosity may range from roughly 200 to 1,000 Pa·s across shear rates of 100–1,000 s⁻¹ depending on rubber content and temperature; these values are representative and must not substitute for on-site rheological verification.

Filament diameter stability is the primary extrusion quality criterion. Production-scale single-screw filament lines with L/D 24:1 to 30:1, downstream gear pumps, and 60–80 mesh melt filtration control ovality to ±0.05 mm when water-bath temperature is held between 40 °C and 60 °C. Lower quench temperatures can freeze the surface before the core has densified, increasing void content and creating dimensional spikes that trigger extruder slip in Bowden-driven machines. Laser micrometer logging at 1 Hz or faster is recommended for lot acceptance; any spool showing runout above 0.07 mm should be segregated from product runs requiring unattended operation.

When the Natural Color Grade Is Run on a Heated Build Plate Without an Enclosed Chamber

Flat rectangular sections longer than 100 mm in the X–Y plane generate sufficient shrinkage stress to peel the part from an unheated platform. For this natural ABS, the build-plate temperature should be set to 90 °C–110 °C, with 110 °C held only when the machine bed thermistor is calibrated and the first layer is deposited at 0.20–0.25 mm thickness. Adhesion on borosilicate glass is improved with a thin ABS-acetone slurry or a polyetherimide sheet; textured PEI surfaces reduce the need for slurry but can produce excessive adhesion at the upper temperature boundary. An actively heated chamber at 60 °C–80 °C is the control variable that most reduces in-plane warpage in sections above 150 mm by maintaining the part above the glass transition of the SAN-rich phase during layer accumulation. Without chamber control, corner lift at edges is most likely when the layer time falls below 20 s and the ambient air temperature is below 20 °C.

Mechanical properties of unfilled ABS printed in the X–Y build plane are frequently compared with injection-moulded values but are anisotropic because the filament weld line is a weak boundary. Representative ranges for unfilled ABS, conditioned at 23 °C and 50 % RH, are listed below; the natural-color Clariant grade should be confirmed against these reference windows before being substituted into load-bearing fixtures.

Tensile specimens printed according to ISO/ASTM 52921:2013 or ASTM D638-14 in the flat orientation typically retain 80–100 % of the injection-moulded tensile modulus in the X–Y plane, while the Z-direction tensile strength may be 40–60 % of the in-plane value because layer adhesion is a time-temperature-pressure welding process rather than a bulk continuum property. Natural unfilled ABS does not achieve the interlaminar strength of filled or chemically coupled formulations; the use of soluble adhesive primers or vapor smoothing can alter surface gloss and critical fit dimensions but does not convert the laminate interface into a homogeneous phase.

Differences from Pigmented ABS, PLA, and ASA in the Same Printing Cell

Against pigmented ABS, the natural color product removes the particle-size distribution and thermal conductivity contribution of colorants. Carbon black, titanium dioxide, and iron oxide can raise melt viscosity and change solidification rate; their absence in natural ABS tends to produce a more translucent side wall, slightly lower visual hiding power, and less particulate abrasion on brass nozzles over multi-spool runs. It also removes one source of lot-to-lot color drift, although base-resin yellowness and stabilizer consumption can still shift appearance. Against unfilled PLA, natural ABS requires a higher bed temperature, emits aromatic styrene during extrusion, and shows greater warpage; in return it offers higher heat deflection and a failure mode that is more ductile than brittle PLA. Against ASA, the natural ABS product has lower outdoor UV resistance because the unsaturated butadiene rubber phase is susceptible to photo-oxidation; ASA’s acrylic rubber gives better gloss retention and yellowing resistance in exterior applications. The processing differences are most visible in the first 5 mm of the build: ABS demands a consistently heated build chamber and carefully managed first-layer adhesion, whereas PLA tolerates rapid cooling and ASA often requires similar thermal conditions to ABS but with less residual styrene release.

Acetone vapor smoothing and solvent bonding are common for natural ABS because the lack of pigment eliminates one secondary phase that can form surface haze during chemical finishing. Ketone-based solvents penetrate the SAN-rich surface and can seal the interlayer void network; however, dimensional tolerance may shift by 0.1–0.3 % on large faces if exposure time exceeds 15–30 s in uncontrolled vapor. Machining and tapping of natural ABS printed blocks is generally possible with high-speed steel or carbide tools at low spindle speeds, but the rubber phase can generate heat-softened burrs if the tool dulls. Cyanoacrylate adhesives and ABS pipe cements produce joints with higher bond strength than the Z-direction tensile layer but can stress-crack thin walls under excessive solvent loading.

Drying is a process boundary rather than a cosmetic recommendation. Unfilled natural ABS filament exposed to relative humidity above 60 % for more than 24 h can absorb enough surface moisture to generate steam-induced porosity during nozzle residence. A forced-air or vacuum dryer should hold the spool at 70 °C–80 °C for 4–6 h before long prints; spools already brittle from hydrolytic degradation should be discarded because no amount of drying restores rubber-phase toughness. Storage in sealed polyethylene bags with desiccant below 20 % RH is the standard preventive control.

Ventilation must be engineered for the styrene, acrylonitrile, and low-molecular-weight thermal degradation products released during extrusion at 220 °C–250 °C. The filament is not rated for direct food-contact applications, is not designed for medical implant use, and should not be autoclaved above 100 °C because the part will distort below the reported HDT. For fire-related compliance, unfilled ABS printed parts are typically described as UL 94 HB; if a V-class rating is required, the natural-color material should be tested in the final printed configuration because flame retardant additives are not specified in this grade.