The Clariant Natural Polyamide 6 3D Printer Filament is supplied as an unfilled, natural-coloured polyamide 6 monofilament for fused filament fabrication. It is available in nominal diameters of 1.75 mm and 2.85 mm, with a typical diameter tolerance of ±0.05 mm. The product designation is an unfilled natural PA6 filament without added carbon black, titanium dioxide, or organic pigments, so melt clarity and contamination can be inspected after drying. Packaging is commonly supplied in 750 g and 2.5 kg spool configurations, although converter-specific packaging may differ.

Filament ovality and diameter consistency are measured on production lines with two-axis laser gauges. Control of ovality is critical because PA6 is hygroscopic and dimensional variation beyond 0.05 mm can produce extrusion-flow instability. Spools are wound with controlled traverse tension to avoid core collapse, filament overlap, and frictional scuffing that would damage the natural surface. Unfilled PA6 has a nominal density of 1.13–1.15 g/cm³ when tested according to ISO 1183-1:2019. Melt volume-flow rate for unreinforced PA6 extrusion grades measured at 235 °C under a 2.16 kg load according to ISO 1133-1:2022 typically falls between 20 cm³/10 min and 30 cm³/10 min. Lot-specific values should be verified against the certificate of analysis, because residual moisture and drying history shift apparent viscosity.

What Processing Window Is Required for Unfilled Polyamide 6 Extrusion?

Polyamide 6 is hygroscopic and process-stable only after drying. The filament should be dried in a dry-air dryer at 80 °C for 4–8 h, with a dew point at or below −20 °C, to reach a residual moisture target below 0.05 wt%. At relative humidity above 60 %, direct exposure to ambient air for more than 30–60 min can raise surface moisture sufficiently to generate steam voids at the nozzle. When a vacuum oven is used instead of a dry-air dryer, drying at 80 °C for 8 h under reduced pressure is often sufficient. Desiccant dryers without verified dew-point control are not reliable for PA6 because the material releases moisture rapidly during heating.

Printing is typically conducted with a nozzle set point of 250–270 °C, a heated bed at 60–90 °C, and an enclosed chamber at 35–50 °C. Part cooling air is usually disabled for the first layer and limited to 0–20 % thereafter to avoid crystallisation stress and layer splitting. Print speeds of 30–60 mm/s are typical for unfilled PA6. For direct-drive extruders, retraction distances of 0.8–2.0 mm reduce nozzle weep; Bowden extruders generally require 4–6 mm. A hardened steel or stainless nozzle is not required for natural unfilled PA6 because abrasive fillers are absent.

Melt residence time in the hot end should be limited. At 270 °C, idle residence beyond 15 min can initiate thermal-oxidative yellowing and molecular-weight loss. If a machine pause exceeds this threshold, the nozzle should be purged and the filament retracted into a cooled zone. The filament path from dryer to extruder should be sealed and purged with dry air if ambient relative humidity exceeds 60 %.

Typical mechanical and thermal reference data for unfilled natural PA6 filament are given in Table 1. The values are general unfilled PA6 data; Clariant product-specific batch data should be obtained from the current technical datasheet. Printed FFF tensile data frequently fall below injection-moulded datasheet values because of residual void content and raster-direction anisotropy.

When Natural PA6 Replaces PLA, PETG, or ABS in Functional Prototypes

Natural PA6 occupies a different material-selection position than PLA, PETG, ABS, and PA12. PLA has higher dry stiffness and easier printability but fails at lower temperature and shows brittle fracture. PETG has lower moisture sensitivity and less warpage but lower heat deflection temperature than PA6. ABS offers similar heat resistance but poorer resistance to oils and aliphatic hydrocarbons. Unfilled PA6 has a dry tensile strength of 65–80 MPa, which is above typical PLA, PETG, ABS, and PA12 ranges. Its heat deflection temperature at 1.8 MPa is 65–85 °C, similar to PETG and below ABS but higher than PLA. Compared with PA12, PA6 absorbs more moisture, has higher stiffness and tensile strength, and usually shows greater warpage because of higher crystallisation shrinkage.

Warpage must be considered when PA6 substitutes PETG or PLA. Unfilled PA6 exhibits linear mould shrinkage of 1.0–1.5 %, whereas PLA and PETG typically show lower and more isotropic contraction. FFF parts from PA6 therefore require higher chamber heat, a adhesion primer or polyvinylpyrrolidone-based glue, and often brim or raft structures.

Compared with carbon-fibre or glass-fibre filled PA6, the natural unfilled filament has lower tensile strength and lower modulus but greatly reduced nozzle abrasion. It contains no conductive carbon and is not electrostatically dissipative. Published data for this specific Clariant unfilled natural filament in fibre-filled comparative trials are limited, but the general property trend is well documented for PA6 compounds.

Moisture Uptake, Interlayer Adhesion, and Shrinkage Compensation

Moisture is the dominant process variable. At 23 °C and 50 % RH, unfilled PA6 absorbs 2.5–3.0 wt% water; saturation in water reaches 9–10 wt%. Water plasticises the amorphous phase and reduces tensile strength and modulus while increasing impact toughness. Reported strength reductions for saturated unfilled PA6 frequently fall between 30 % and 50 % relative to dry values, so dry-as-printed data are not sufficient for wet-service design. Dried filament must be fed from a sealed dry box or active desiccant hopper; exposure in a humid print room can exceed the safe moisture threshold within 1–2 h.

The water absorption reaction is reversible. Drying printed parts at 80 °C for 6–10 h removes a substantial fraction of absorbed moisture, but rapid water uptake begins again on exposure. Design calculations should use conditioned properties when service humidity is above 50 % RH.

Interlayer adhesion in fused filament fabrication is governed by polymer diffusion across the weld line. Reported Z-axis tensile strengths of unfilled PA6 printed specimens typically reach 40–70 % of the XY tensile strength when the chamber and nozzle temperatures are held near the upper limits and layer times are short. Lower chamber temperatures or high fan speeds reduce local melt temperature and deposit poorly fused layers. The use of a sacrificial raft, brim, or PA-specific adhesion primer on glass or carbon-fibre build plates reduces corner lifting. Unfilled PA6 exhibits crystallisation shrinkage and anisotropic part contraction; linear mould shrinkage values of 1.0–1.5 % are common for injection-moulded PA6, while FFF parts show raster-dependent contraction that can exceed 0.5 % in long unsupported sections. Scaling compensation in the slicer is usually required for features longer than 100 mm.

Solidification and crystallinity are also process-sensitive. Non-isothermal DSC according to ISO 11357-7 indicates crystallisation onset for PA6 typically in the range of 170–180 °C at cooling rates of 10–20 °C/min. In a heated chamber, slower cooling raises crystalline content and can improve modulus and creep resistance, but increases layer-time-dependent shrinkage and warpage. Rapid cooling with a fan suppresses spherulite growth and can reduce interlayer crystalline bridging, lowering Z-axis strength. The natural unfilled grade has no nucleating pigments, so crystallisation behaviour is governed mainly by melt temperature, cooling rate, and moisture.

Unfilled natural PA6 resists aliphatic hydrocarbons, mineral oils, greases, many ketones, esters, and dilute alkali solutions at ambient temperature. It is attacked by strong acids, phenols, chlorinated solvents under stress, and strong oxidising agents. Continuous immersion in boiling water or hot ethylene glycol is not recommended because hydrolysis and plasticisation reduce molar mass and load-bearing capacity. Published data for this specific Clariant natural filament in prolonged hot-water service are limited; printed parts should be exposed to end-use fluids only after physical testing of finished samples.

Post-print annealing can be carried out at 80–100 °C for 1–4 h in mineral oil or moisture-controlled air to increase crystallinity and stabilise dimensions. Annealing produces dimensional change of 0.5–1.5 % and may darken the natural colour. Machining of printed PA6 is feasible by reaming, tapping, and thread forming if cutting temperatures are kept low; local frictional heating above the melt point can smear the surface.

RoHS, REACH, and Food-Contact Boundaries Are Not Interchangeable

Regulatory documentation for the raw filament includes safety data sheets and lot traceability. REACH SVHC content declarations are made under Article 33 of Regulation (EC) No 1907/2006. RoHS compliance is assessed against Annex II of Directive 2011/65/EU. The natural unfilled PA6 raw material is not automatically compliant with food-contact requirements; no FDA 21 CFR 177.1500 determination should be assumed for printed parts because voids, surface roughness, and additive migration are process-dependent. For applications requiring food-contact, medical, or potable-water suitability, the printed component must be validated under the relevant end-use standard.

Continuous service under mechanical load should not exceed approximately 60–80 °C in air for unfilled PA6, because oxidative embrittlement and creep limit long-term performance. Short-term exposure to 120 °C may be tolerated only for unstressed or lightly loaded parts. The heat deflection temperature measured at 1.8 MPa is a short-time test and does not define a continuous use temperature. Field observations on production-scale equipment identify three recurring failure modes: steam voids from undried filament, nozzle jams from excessive retraction or melt residence, and build-plate delamination when chamber temperature is below 35 °C or when the bed coating is contaminated. The filament should not be held at 270 °C or above for more than 15 min without extrusion. Avoid amine-based bed adhesives because they can dissolve or stress-craze the lower surface of the part. If a machine pause exceeds the melt residence threshold, the nozzle should be purged and the filament retracted into a cooled zone.