Clariant Natural Polycarbonate 3D Printer Filament is an unfilled, natural-grade thermoplastic feedstock based on bisphenol-A polycarbonate supplied for fused filament fabrication. The material is distributed in 1.75 mm and 2.85 mm diameter formats, with typical spool net weights of 0.75 kg or 1 kg where regional packaging permits. Unlike pigmented or compounded polycarbonate grades, the natural variant contains no visible colorant and exhibits translucency after processing; optical transmission is lower than cast polymethyl methacrylate because printed layer interfaces, flow lines, and microvoids scatter light. Dimensional acceptance is commonly referenced to ISO 286-1 limit designations or supplier-specific laser-gauge records, with roundness deviation monitored to ±0.05 mm for 1.75 mm feedstock. The material is intended for functional prototypes, fixtures, jigs, and short-run tooling where higher temperature resistance and impact strength are required relative to acrylonitrile-butadiene-styrene and poly(ethylene terephthalate) glycol. Published data for this specific configuration is limited when no distributor-controlled datasheet accompanies the lot; the following sections therefore use reference data for unfilled polycarbonate filament and identify where end-user verification is required.

Why Does Residual Moisture Dictate the Lower Usable Barrel Temperature?

Moisture uptake is the controlling pre-processing variable for polycarbonate. Unfilled bisphenol-A polycarbonate filament exposed to 23 °C and 50 % RH typically equilibrates to 0.15–0.20 wt% water; at 60 % RH the value can exceed 0.25 wt%. Extrusion stability with a 1.75 mm filament requires a residual moisture content below 0.02 wt%. Above 0.03 wt%, hydrolytic chain scission during the 260–300 °C melt residence produces surface splay, reduced interlayer tensile strength, and visible voids in the weld bead. Drying is performed in a forced-convection oven or desiccant dryer at 80 °C for 6–12 h, or in a vacuum oven at 80 °C and pressure below 50 mbar for 4–8 h. Desiccant dryers should deliver a dew point no higher than -40 °C. Spools removed from sealed packaging at ambient humidity above 60 % are pre-dried before printing. A dry box or heated filament cabinet maintained at 60–70 °C with a desiccant bed is advised for long builds exceeding 8 h. Batch-to-batch variance in moisture content has been observed when storage conditions differ across distributor warehouses; a previously opened spool exposed to ambient air for more than 24 h must be re-dried. Failure to dry is not corrected by raising nozzle temperature, because hydrolysis accelerates with temperature and the melt becomes lower-viscosity and gas-laden.

Warp Control, Enclosure Thermal Bias, and First-Layer Adhesion Limits

Polycarbonate solidifies with a coefficient of linear thermal expansion near 65–70 × 10⁻⁶ K⁻¹ below the glass transition. The resulting shrinkage during deposition creates a warping moment at the build-plate interface. The heated bed is set to 90–110 °C for unfilled polycarbonate; below 85 °C, edge lift often begins before the tenth layer in parts with footprints larger than 80 mm. A fully enclosed build chamber stabilized at 60–80 °C reduces the vertical thermal gradient and is required for dimensionally stable sections above 100 mm in the longest axis. Printing without a chamber is possible only for small parts under 50 mm when bed adhesion is optimized. The first layer is deposited at 5–10 °C above the regular bed setpoint, with a first-layer height of 0.20–0.30 mm and a speed reduction to 15–25 mm/s. Adhesion systems commonly use polyetherimide or polycarbonate sheet at 100–115 °C, or adhesive formulations that develop peel strength above 0.2 N/mm at operating temperature. Nozzle temperature for unfilled natural polycarbonate is set between 260 °C and 300 °C, with printed bead tensile strength falling below acceptable limits below 260 °C. The processing window is narrow: a ±5 °C variation around the optimum can shift surface gloss and weld-line strength. Hardened steel or tool-steel nozzles with orifice diameters of 0.4–0.6 mm are recommended; brass nozzles are acceptable at low throughput but show faster wear when filled or reclaimed polycarbonate feedstocks are substituted. Print speeds are typically 30–60 mm/s, with volumetric throughput kept below 8 mm³/s to avoid melt fracture and pressure fluctuation on direct-drive extruders. Retraction distance should be limited to 1–2 mm on direct-drive and 4–6 mm on Bowden systems, with retraction speed below 30 mm/s; excessive retraction pulls humid air into the hot zone and generates nozzle drool or carbonization.

Because melt flow and dimensional tolerance jointly fix the maximum stable deposition rate, unfilled natural polycarbonate filament for fused deposition is characterized by a melt volume-flow rate in the extrusion-grade range rather than injection-molding grades. The value measured at 300 °C under 1.2 kg load according to ISO 1133-1:2022 is commonly 5–12 cm³/10 min. Lower melt flow improves interlayer melt strength but reduces maximum stable volumetric throughput; higher melt flow improves fluent deposition but increases susceptibility to stringing and shorter continuous-use thermal stability. Diameter control is maintained by multi-axis laser gauging during filament production. For reliable feed, a 1.75 mm filament should exhibit ovality no greater than 0.03 mm, while a 2.85 mm filament should remain within ±0.05 mm along the spool. Table 1 lists typical reference data for unfilled polycarbonate filament; these values are not substitutes for lot-specific certificates of analysis.

When High-Temperature Rigidity and Translucency Outweigh Processing Difficulty

Polycarbonate is selected over acrylonitrile-butadiene-styrene when parts must resist creep at service temperatures above 85 °C. ABS typically exhibits heat deflection around 85–100 °C at 1.8 MPa under ISO 75-2, while unfilled polycarbonate remains serviceable to 110–125 °C. Polycarbonate also demonstrates higher notched impact toughness than PETG and ABS, with Izod notched values of 15–30 kJ/m² compared with typical ABS values of 10–25 kJ/m² and PETG values of 5–15 kJ/m²; however, the upper end is dependent on moisture state and fusion quality. Relative to PETG, natural polycarbonate provides higher modulus and much higher heat deflection temperature, but PETG prints at lower bed temperatures and has lower susceptibility to warp. Relative to carbon-fiber-filled polycarbonate, the natural unfilled grade is electrically non-conductive, lower in stiffness, more translucent, and non-abrasive to brass nozzles. Carbon-fiber-filled polycarbonate may reach tensile modulus values above 6,000 MPa, but it sacrifices impact toughness and translucency. The unfilled natural grade is therefore used for translucent light diffusers, prototype electrical enclosures, inspection fixtures, and hot-air ducting where the part must survive brief excursions to 120 °C. It is not the first choice for high-abrasion locating fixtures or for high-cycle injection mold tooling; glass- or carbon-filled polycarbonate or tooling resins are selected there. The processing burden includes drying, enclosure temperatures above 60 °C, and bed temperatures not less than 90 °C, which restrict use on printers without heated chambers or high-temperature beds.

Before lot introduction to production, regulatory screening of the natural unfilled polycarbonate filament is usually assessed against the heavy-metal and restricted-substance requirements of RoHS 2011/65/EU Annex II and the candidate-list obligations of REACH. Because the material is unfilled and uncolored, certain additive-related screening burdens are lower than for pigmented or flame-retarded grades. However, compliance is not self-certified; each production lot must be verified through supplier documentation. Table 2 lists the main screening areas and the relevant test or document type.

On production floors, the filament is used for vacuum forming fixtures, robotic end-of-arm tooling, and inspection gauges where dimensional stability under overhead lighting and brief contact with warm parts is required. A fixture printed at 0.2 mm layer height with 100 % rectilinear infill and annealed at 120 °C for 4 h can withstand contact with workpieces at 100 °C without gross deformation, provided the load is compressive. If the fixture sees clamping forces, the bolted joint should include metallic bushings; direct thread engagement in unfilled polycarbonate at ambient temperature can initiate radial cracking at fastening torques above 1.5 N·m in M5 bosses printed without heat-set inserts. The annealing cycle must use constrained support or a flat platen because printed polycarbonate parts can distort above the glass transition. Annealing also reduces residual stress and improves chemical resistance but may increase opacity slightly in natural translucent sections. Production-scale behavior has shown variable part shrinkage across build chambers when the chamber fan cycles unevenly; parts located near the door may lose interlayer bonding due to a 10–20 °C local air temperature drop. Therefore, thermocouple-logged chamber mapping is recommended before batch production.

Solvent incompatibility remains a strict boundary. The material should not be exposed to ketones such as acetone and methyl ethyl ketone, chlorinated hydrocarbons such as methylene chloride, or aromatic hydrocarbons such as toluene and xylene, because stress cracking or dissolution occurs. Alcohols may be used for mild surface cleaning but should be evaporated before thermal processing. The filament should not be combined with amine-based additives or flame-retardant masterbatch without compatibility testing, because certain amine species accelerate chain scission at processing temperatures. For outdoor use, UV stabilization must be confirmed separately; natural unfilled polycarbonate without UV protection develops yellowing and loss of surface gloss after extended exposure under ISO 4892-2 weathering cycles. End-use parts in continuous contact with water above 70 °C may undergo hydrolytic degradation unless annealed and stress-relieved. Published data for this specific configuration is limited for long-term creep in printed, void-containing geometries, so load-bearing parts require application-specific validation under ISO 899-1:2024 or similar.