Clariant Polylactic Acid Black 3D Printer Filament is supplied as a pigmented polylactide monofilament in nominal diameters of 1.75 mm and 2.85 mm. The commercial designation functions as the grade identifier; no separate numerical model code appears in the consulted technical literature. The compound comprises a semicrystalline PLA carrier resin and a dispersed carbon black pigment system at a loading below 2.0 wt%. Melt volume-flow rate, determined according to ISO 1133-1:2011 at 210 °C and 2.16 kg, falls in the expected range of 8 cm³/10 min to 14 cm³/10 min for this pigment-loaded class. Density is 1.24 g/cm³. Because published data for this specific black formulation is limited, property values in this document are presented as representative ranges for carbon-black-loaded PLA compounds with equivalent filler content rather than as batch-specific values for one production lot.

Dimensional tolerance is specified as ±0.05 mm for 1.75 mm filament and ±0.07 mm for 2.85 mm filament, with ovality not exceeding 0.05 mm. The filament is commonly wound on 1 kg spools and sealed in aluminum-laminated packaging with desiccant sachets before shipment. Storage at 20 °C to 25 °C and 15% RH to 35% RH preserves the dried state; open-spool storage at 60% RH or higher requires pre-drying.

What Distinguishes Black PLA from Natural and Impact-Modified PLA Filaments?

The black grade differs from natural PLA mainly in optical density, crystallization behavior, and melt rheology. Carbon black acts as a heterogeneous nucleating agent; differential scanning calorimetry at 10 K/min typically shows an increase in peak crystallization temperature of 2 °C to 5 °C relative to unfilled PLA when dispersion median particle size remains below 5 μm. The nucleating effect can increase crystallinity after slow cooling and marginally raise the heat deflection temperature, but it can also reduce interlayer fusion at low nozzle temperatures because crystal growth competes with polymer chain diffusion. Compared with natural PLA, the black grade has lower translucency, higher melt density, and slightly lower melt strength. Compared with impact-modified PLA, the material has lower notched Izod impact strength and is not suitable for snap-fit components requiring ductile failure. The following table summarises representative comparative ranges for carbon-black-loaded PLA, unfilled PLA, and ABS.

Dispersion quality is a critical differentiator. If carbon black agglomerates exceed 20 μm, notched Izod impact strength can fall below 2.5 kJ/m² and elongation at break may drop to 1.5%. Masterbatch manufacturing on a 40:1 L/D twin-screw extruder with side feed at 60% of the barrel length is typical for achieving a median particle size below 5 μm. The pigment also raises melt density from approximately 1.08 g/cm³ to 1.12 g/cm³, which changes feed-zone compression behavior during filament extrusion. For applications requiring visible-light shielding, the black pigment provides high optical density and reduces translucency to less than 5% at 2.0 mm wall thickness. This is an advantage for light-shielding housings but a disadvantage for lithophane or backlit display parts.

Pre-drying is mandatory at relative humidity above 60% RH or after open spool storage exceeding 8 h. PLA hydrolysis begins when moisture content exceeds 0.025 wt% at melt temperature; the visible failure modes are filament diameter instability, surface bubbles, and reduced tensile strength. Drying in a desiccant dryer at 60 °C for 4 h to a moisture content below 250 ppm is recommended, with a desiccant bed dew point of -40 °C or lower. Hydrolysis is autocatalytic and accelerates with carboxylic acid end-group concentration. At melt temperatures above 200 °C, moisture at 0.05 wt% can reduce molecular weight by 20% to 30% within 2 min, as measured by gel permeation chromatography. This is why closed-loop desiccant dryers are used instead of simple hot-air ovens in production. The black pigment can mask early yellowing, so moisture-induced damage may not be detected until tensile strength falls below 45 MPa. Incoming QC using a Karl Fischer titration method or a moisture analyzer calibrated for PLA should reject filament above 0.035 wt% moisture.

On a production single-screw filament extrusion line with 25:1 L/D, 2.5:1 compression ratio, and melt pump, a typical melt temperature profile is 180 °C in the feed section, 210 °C in compression, and 205 °C at the die. The die diameter is 2.0 mm for 1.75 mm finished monofilament, and the draw ratio after air-gap cooling is 1.3:1. Batch-to-batch variation in carbon black dispersion can shift melt volume-flow rate by ±1.5 cm³/10 min; incoming QC should therefore include melt flow index testing and optical microscopy at 50× for agglomerate detection.

When Melt Temperature Deviates Outside the Recommended Envelope

The recommended nozzle temperature window for the black PLA filament is 190 °C to 220 °C. Below 185 °C, the melt viscosity rises sharply; carbon black raises low-shear viscosity more than high-shear viscosity, which can suppress oozing during travel moves but may cause under-extrusion and poor layer fusion. At 230 °C and above, PLA undergoes chain scission and lactide regeneration; the melt phase becomes increasingly Newtonian and strand melt strength collapses. Thermogravimetric analysis at 10 K/min in nitrogen indicates the onset of mass loss near 300 °C, but residence time above 230 °C for more than 5 min can already produce yellowing and molecular weight reduction. Capillary rheometry at 210 °C shows shear-thinning behavior; apparent viscosity at 100 s⁻¹ is typically 400 Pa·s to 800 Pa·s for PLA compounds of this melt flow class. The effective processing window is narrower than unfilled PLA by approximately 5 °C at the upper end when carbon black loading exceeds 1.0 wt%.

Differential scanning calorimetry under 10 K/min nitrogen reveals a glass transition at 55 °C to 60 °C, cold-crystallization exotherm onset near 95 °C to 110 °C, and melting endotherm peak at 165 °C to 180 °C for PLA compounds of this class. Carbon black loading below 2.0 wt% raises peak crystallization temperature and reduces cold-crystallization enthalpy because the particles provide nucleation sites. Isothermal crystallization half-time at 110 °C is reported in the literature as 2 min to 5 min for unfilled PLA; carbon black can reduce this half-time by 10% to 30%. These kinetic parameters explain why heated chambers above 40 °C are not required and why bed temperatures above 60 °C can cause first-layer deformation under extrusion pressure.

The upper print speed is limited by melt strength. At infill speeds above 80 mm/s with a 0.4 mm nozzle, the filament can exhibit melt fracture and irregular bead width because the apparent shear rate at the nozzle wall approaches the critical shear rate for PLA. A volumetric flow rate of 8 mm³/s to 10 mm³/s is stable; above 12 mm³/s, the melt transitions from plug-like flow to wall slip, and the extruder stepper motor may lose steps if the nozzle pressure drop exceeds 10 MPa. These values are observed on production FDM equipment for carbon-black-loaded PLA compounds and can vary with nozzle geometry.

On a production FDM platform equipped with a direct-drive extruder and a 0.4 mm hardened steel nozzle, settings of 210 °C nozzle temperature, 50 °C bed temperature, 60 mm/s infill speed, and 0.8 mm retraction distance at 40 mm/s reduce stringing and maintain interlayer adhesion. Build plate adhesion is achieved on glass or polyetherimide beds with a polyvinyl alcohol-based adhesive at 50 °C; bed temperatures above 65 °C are not recommended because the contact surface approaches the heat deflection temperature. When printing a Type 1BA tensile specimen at 100% infill flat on the bed, interlayer tensile strength measured by ISO 527-2:2012 is typically 35 MPa to 45 MPa, or 70% to 80% of the bulk tensile strength. This reduction is attributable to incomplete polymer chain diffusion across the layer interface and is a known limitation of PLA FDM processing rather than a specific defect of the black grade.

Regulatory Status and Material Safety Boundaries

The compound is expected to conform to RoHS 2 2011/65/EU as amended by 2015/863 for lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, polybrominated diphenyl ethers, and the four restricted phthalates. REACH SVHC screening to 0.1 wt% per article is required for each batch because carbon black feedstocks may contain trace polycyclic aromatic hydrocarbons depending on the source and post-treatment. Carbon black as a bound pigment does not present an inhalation hazard during printing; however, sanding or machining printed parts can generate respirable particulate and should be performed with local exhaust ventilation. No claim is made for compliance with FDA 21 CFR food-contact provisions because black pigment systems and processing aids are not universally listed. The following checklist identifies the primary standards applicable to incoming inspection and printed-part qualification.

Applications are limited to non-load-bearing housings, jigs, fixtures, signage, and visual prototypes that do not require continuous service above 55 °C. The black grade is not a replacement for ABS or PETG in under-hood automotive parts because the heat deflection temperature at 0.45 MPa is at least 35 °C lower. Against carbon-fiber-reinforced PLA, the black pigment grade has lower tensile modulus by roughly 1.2 GPa to 2.0 GPa and is non-abrasive to brass and hardened steel nozzles. Against PETG, the black PLA has lower impact strength and lower humidity resistance but higher stiffness and less stringing at equivalent retraction settings. Against ABS, the black PLA produces lower volatile organic compound emissions and lower shrinkage, but it cannot be acetone vapor-smoothed and has inferior thermal resistance. Chemical resistance is limited to weak acids and alcohols; esters, ketones, and strong alkalis cause stress cracking and should be avoided. The material is not intended for direct food-contact applications unless a specific regulatory grade is certified, because pigments and processing aids can migrate under aqueous and fatty simulants.