Clariant Black Polyamide 6 3D Printer Filament is supplied as an unfilled, black-pigmented polycaprolactam feedstock for fused filament fabrication and direct material extrusion. The material is identified in supplier documentation by polymer family and colorant state rather than by a separate numerical model designation; grade-specific values are traceable through lot-level certificates. Nominal filament diameters are 1.75 mm and 2.85 mm; dimensional conformity is verified by two-axis laser micrometry with a resolution of 0.01 mm, and commercial tolerance limits for diameter and roundness are commonly specified at ±0.05 mm. Density of the conditioned polymer is approximately 1.13 g/cm³ at 23 °C and 50 % relative humidity when measured according to ISO 1183-1. The base resin is polycaprolactam with repeating amide linkages along the polymer backbone; the black colorant is dispersed during compounding on a co-rotating twin-screw extruder with an L/D ratio between 32:1 and 44:1, followed by melt filtration before filament drawing. Typical mechanical values for unfilled PA6 conditioned to equilibrium at 23 °C and 50 % relative humidity fall within tensile modulus 2,800–3,300 MPa per ISO 527-2, tensile stress at yield 70–85 MPa, and notched Charpy impact 4–6 kJ/m² per ISO 179-1/1eA. Heat deflection temperature under 0.45 MPa load is typically 160–180 °C per ISO 75-2/B, and Vicat softening temperature under 50 N load is approximately 200 °C per ISO 306/B50. These are unfilled polyamide 6 reference ranges; printed part values depend on build orientation, extrusion temperature, and moisture state. Published data for this specific black-pigmented Clariant filament configuration are limited, so lot-level certificates remain authoritative for design calculations. On receipt, the spool should be checked for vacuum seal integrity, because polyamide 6 moisture uptake begins as soon as the barrier bag is opened. A calibrated micrometer measurement at three points per metre can detect diameter drift; irregularities above 0.07 mm across a 10-metre sample can produce feed-path jams in direct-drive extruders. Filament roundness below 0.95, calculated as minimum diameter divided by maximum diameter, may cause inconsistent retraction and leakage at the hot-end seal. These checks are observed on production lines where open-bay storage is common, and they reduce dimensional rejects in large build jobs.

Does the Black Pigmentation Modify Nucleation, Surface Resistivity, or Ultraviolet Stability?

Black pigmentation in polyamide 6 is generally introduced as a carbon black masterbatch or as a soluble colorant system. Carbon black can act as a nucleating agent, increasing crystallisation rate and raising the crystalline fraction under fast cooling. In extrusion and injection moulding, this may increase melt viscosity and die pressure slightly; in fused filament fabrication, the effect is observed as a marginal reduction in oozing when print temperature is held constant. Carbon black also absorbs ultraviolet radiation and can reduce photodegradation at the exposed surface of outdoor parts. Surface resistivity may shift from the insulating range of unfilled PA6, typically above 10^12 Ω/sq per IEC 62631-3-2, to a lower antistatic range if carbon black loading is sufficiently high; however, no conductivity claim is made for this product unless a separate specification is provided. The black colorant masks oxidative yellowing, which removes one visual indicator of thermal degradation; melt temperature and residence time must therefore be controlled by direct measurement rather than colour change. Pre-drying in a desiccant dryer at 80 °C for 4 h to 8 h reduces residual moisture below 0.02 % by weight, the threshold commonly required to prevent hydrolysis-induced bubble formation and interfacial weakness in polyamide 6. Spools removed from sealed packaging and held in air at 60 % relative humidity can regain 0.1 % moisture within 24 h; at 80 % relative humidity, surface moisture uptake is faster, and dry-box storage at 30–40 °C with a dew point below −20 °C is recommended for continuous operation. Hydrolysis in the melt phase cleaves amide linkages, lowers molecular weight, and produces voids at the nozzle. On production machines, moisture-induced extrusion variation appears as oscillating filament diameter at the nozzle tip, poor interlayer fusion, and steam ejection during rapid retraction. If a spool has been left unprotected in humid air, drying should be extended to 12 h at 80 °C only after confirming the spool core is not softened; temperatures above 100 °C may accelerate oxidative degradation even though the black colour masks yellowing. Residual moisture is typically verified by Karl Fischer titration or by weight-loss methods per ISO 15512; the 0.02 % limit corresponds to approximately 200 ppm water. Gravimetric analysis after drying at 80 °C for 24 h may overestimate moisture if volatile oligomers are released; therefore Karl Fischer titration is preferred for polyamide 6. Rheologically, unfilled PA6 in the melt state typically shows a melt volume-flow rate of 10–20 cm³/10 min at 250 °C and 2.16 kg load per ISO 1133-1. The black-pigmented grade may fall at the lower end of this range because a well-dispersed colorant can increase melt viscosity. Stable filament feeding through a 0.4 mm nozzle requires melt pressure below the extruder drive limit; direct-drive systems with dual-drive hardened gears reduce filament deformation when retraction distance is limited to 1–2 mm at 20–30 mm/s. Bowden systems typically require 4–5 mm retraction and may benefit from a 0.6 mm nozzle to lower backpressure.

Build Platform, Chamber, and Nozzle Settings for Open-Architecture FFF Systems

Polyamide 6 solidifies with higher volumetric shrinkage than amorphous PETG or PLA, so bed adhesion and chamber temperature control are dominant process variables. A build platform temperature of 80–100 °C is used with adhesion media such as polyvinyl alcohol-based glue, polyamide-specific films, or glass-fiber epoxy substrates. On open-architecture machines without a heated chamber, enclosure temperature is typically maintained between 45 °C and 60 °C to reduce thermal gradients. A hardened steel or stainless-steel nozzle of 0.4 mm or 0.6 mm is preferred for consistent melt flow; brass nozzles are acceptable for unfilled material but exhibit increased bore wear when carbon black is present at high loadings. Extrusion temperatures from 240 °C to 270 °C are typical, with first-layer adhesion often improved at the upper end of the range. Print speeds of 30–60 mm/s and layer heights of 0.10–0.25 mm allow sufficient interlayer diffusion; excessive speed below 240 °C produces delamination and low Z-axis tensile strength. For build plates larger than 300 mm × 300 mm, thermal gradients across the plate can cause corner lifting at the perimeter; adhesion strength from polyvinyl alcohol layers varies with ambient moisture and surface preparation. Residence time in the hot end should not exceed 10 min at temperatures above 260 °C; prolonged exposure leads to chain scission and a progressive increase in melt flow rate, which can be mistaken for moisture-related viscosity loss. The black colour masks yellowing, so thermal degradation is usually detected by spatter, a sharp acrid caprolactam odour, or a measurable increase in melt volume-flow rate rather than by visual inspection.

When Black PA6 Replaces PETG or PA12 in Functional Prototypes

Selection of black PA6 over PETG is justified when continuous service temperature or abrasion resistance exceeds the practical limit of PETG. The heat deflection temperature of PA6 under 0.45 MPa load is roughly 160–180 °C, whereas PETG typically deflects at 70–80 °C under the same condition. PA6 also resists aliphatic hydrocarbons and many lubricating oils better than PETG or PLA. Selection over PA12 is based on higher tensile modulus and lower feedstock cost, with the trade-off of higher moisture uptake and greater warpage. PA12 absorbs less than 1 % moisture at 50 % relative humidity, while PA6 can absorb 2.5–3.5 %; dimensional expansion and modulus reduction in humid environments are therefore greater for PA6. The table below summarises comparative property ranges for unfilled PA6 filament and common FFF comparator materials; values are typical ranges for conditioned or printed specimens, not guaranteed product specifications.

Comparative property ranges for unfilled PA6 filament and common FFF comparator materials

Property	Test standard	Black PA6 filament	PETG	PLA	PA12
Tensile stress at yield, XY printed	ISO 527-2	45–65 MPa	40–55 MPa	50–65 MPa	35–50 MPa
Tensile modulus	ISO 527-2	2,800–3,300 MPa	2,000–2,400 MPa	3,000–3,500 MPa	1,400–1,800 MPa
Heat deflection temperature at 0.45 MPa	ISO 75-2/B	160–180 °C	70–80 °C	50–60 °C	90–110 °C
Moisture uptake at 50 % RH	ISO 62	2.5–3.5 %	0.2–0.4 %	0.3–0.5 %	0.7–1.0 %
Typical heated bed temperature	process recommendation	80–100 °C	60–80 °C	20–60 °C	90–110 °C

Compared with carbon-fibre-filled PA6 grades, the unfilled black PA6 filament has lower tensile modulus and lower nozzle abrasion, but higher elongation at break and lower tendency to warp. Glass-filled PA6 similarly increases modulus and reduces thermal expansion but reduces surface finish and increases nozzle wear. The unfilled grade is therefore less demanding on hardened tooling than filled PA6, although a hardened nozzle remains recommended for black pigmented material.

Mechanical Property Ranges in Dry and Moisture-Conditioned Printed Specimens

Polyamide 6 printed properties shift with moisture. Dry-as-moulded specimens tested immediately after annealing show higher tensile strength and modulus but lower impact resistance; conditioned specimens at 50 % relative humidity show lower modulus and yield stress but higher elongation at break. This plasticisation effect is reversible but affects dimensional fit. For printed parts, Z-axis tensile strength is typically 25–40 MPa in dry condition and may decrease by 10–20 % after moisture conditioning because interlayer interfaces absorb water. The material should be annealed at 80–100 °C for 30–60 min to relieve residual stress, but annealing outside the fixture may cause distortion in thin walls. Tensile properties measured on printed specimens according to ASTM D638-14 Type IV are highly orientation-dependent; XY specimens generally yield 45–65 MPa tensile stress, while Z specimens produce 25–40 MPa because layer adhesion limits failure. Operational boundaries for this material include a maximum continuous service temperature of approximately 120 °C under low mechanical load; above this, oxidative degradation accelerates and the polymer embrittles over time. The filament should not be exposed to concentrated sulfuric acid, formic acid, phenolic solvents, or strong oxidising media, which attack polyamide 6. Continuous contact with boiling water or steam above 100 °C accelerates hydrolysis, particularly in thin walls. For industrial applications requiring food-contact compliance, the specific pigment package and processing additives must be confirmed against FDA 21 CFR 177.1500 or EU 10/2011; the base PA6 resin may comply, but the black colorant system requires separate documentation. Published data for this specific configuration on migration testing is limited. For general industrial use, the material is typically supplied with a statement of conformity to REACH and RoHS Directive 2011/65/EU; lot certificates should be checked before deployment.