Clariant Natural Color Polyethylene Terephthalate Glycol 3D Printer Filament is an unfilled glycol-modified polyethylene terephthalate copolymer supplied as round monofilament. The product is identified by its polymer chemistry—poly(ethylene terephthalate-co-1,4-cyclohexanedimethanol terephthalate)—rather than by a single universal article number across all distribution regions. Where a manufacturer-specific item code is required, the procurement specification should list “PETG natural” as the material descriptor together with diameter and spool mass. The natural-color configuration contains no carbon black, titanium dioxide, or organic colorant in the melt stream, so the extruded filament retains the intrinsic translucency of the copolymer. Regional packaging for this product class commonly includes 1.75 mm and 2.85 mm diameters, a diameter tolerance of ±0.05 mm, a roundness deviation of ≤0.03 mm, and net spool masses of 750 g or 1 kg. Because colorant carriers can alter melt flow and crystallization nucleation, the unpigmented grade is often used as a process-qualification baseline for downstream filament extrusion and printability trials. Lot-specific dimensions, moisture content, and melt flow are controlled by the certificate of analysis; published data for the exact Clariant natural-color configuration is limited, and the following technical discussion uses unfilled PETG copolyester data that must be verified against the lot-specific document.

What Is the Role of Cyclohexanedimethanol in Suppressing PET Crystallization?

The copolymer contains 1,4-cyclohexanedimethanol units that replace a portion of ethylene glycol. The cycloaliphatic ring disrupts chain packing and reduces the rate of spherulitic crystallization that otherwise embrittles polyethylene terephthalate during slow cooling from the melt. Differential scanning calorimetry of unfilled PETG in this class typically shows a glass transition temperature near 78–80 °C and no sharp melting endotherm, whereas a semi-crystalline PET filament may exhibit a peak melting temperature near 245–260 °C. The result is an amorphous natural-color filament that can be printed with lower volumetric shrinkage than semi-crystalline PET and with a wider processing window than unmodified PET. The natural color is not merely aesthetic: because no pigment particles are present, the solidification front does not encounter nucleating surfaces that can trigger local crystallinity and haze. However, the absence of pigment also removes a source of melt stiffness; unpigmented PETG may string more readily than pigmented grades at the same nozzle temperature. For applications where translucency is secondary, a pigmented PETG can be selected to alter the flow behavior, but that changes the comparison basis against this natural-color product.

In fused filament fabrication, the material is processed at a nozzle setpoint of 230–250 °C and a bed setpoint of 70–80 °C. The melt volume rate of unfilled PETG in this product class is typically 8–15 cm³/10 min at 250 °C under 2.16 kg load per ISO 1133-1:2022, but the actual melt temperature inside a hot end may differ from the setpoint by ±5 °C depending on thermistor calibration and heater block geometry. This offset is operationally significant because the processing window is narrow: below 230 °C, melt viscosity rises enough to reduce interlayer diffusion and produce delamination; above 255 °C, the natural-color melt may generate acetaldehyde and shift from water-white to yellow if the residence time exceeds 20–30 min. The result is a practical processing window of ±5 °C around the optimal setpoint on many bench-scale printers. For 1.75 mm filament, a direct-drive extruder typically uses retraction of 1.5–3.0 mm at 30–40 mm/s, while a Bowden feed path may require 4–6 mm at 25–35 mm/s. Part-cooling fan speed is held between 20% and 50% after the first layer; higher fan speeds can freeze the strand surface before interlayer welding is complete, lowering Z-axis tensile strength. Layer height between 0.10 mm and 0.20 mm and print speed between 40 mm/s and 80 mm/s are common for unfilled 1.75 mm PETG, but the acceptable range depends on hot-end heat capacity and nozzle orifice diameter. A 0.4 mm brass nozzle works for short runs; a hardened steel nozzle may require a 5–10 °C higher setpoint due to lower thermal conductivity. With a 0.25 mm nozzle, the extended shear stress can generate local melt temperatures above the setpoint, so the practical speed ceiling drops to 30–50 mm/s on unvented hot ends. Batch-to-batch variance in melt flow rate of unfilled PETG can be ±1.5 cm³/10 min; this matters when reproducing identical tool paths across spools. If a new spool shows stringing at the previously validated retraction settings, the first corrective action is to dry the filament and verify the actual hot-end temperature with an external probe. On a production-scale twin-screw extrusion line with L/D 40:1, the transition from pigmented to natural-color PETG can shift the melt-pressure reading at the die by 5–10% because pigment particles alter wall slip and shear heating. Filament producers compensate by adjusting barrel zones 2–4 rather than by changing the die. In printing, this upstream variance may appear as spool-to-spool differences in die swell and stringing. Published data for this specific Clariant configuration is limited; therefore, the values given here are not a substitute for a printer-specific process qualification.

If a Moisture-Laden Spool Is Loaded Directly into a Bowden Extruder, Hydrolytic Degradation Can Begin Before the Melt Leaves the Nozzle

Unfilled PETG absorbs enough atmospheric moisture to generate extrudate voids when the moisture content exceeds 0.04 wt%. Pre-drying at 65 °C for 4–6 h in a desiccant dryer with a dew point below −30 °C reduces moisture to ≤0.02 wt% as determined by ISO 15512. In a Bowden system, the long feed path delays the escape of water vapor and increases the probability of back-pressure fluctuations at the melt zone. Hydrolysis cleaves ester linkages, lowering molecular weight and reducing interlayer fracture resistance even when visible bubbles are absent. The failure mode can be non-obvious: a wet spool may print with acceptable visual quality but show a measurable drop in Z-axis tensile strength. Storage above 60% relative humidity without a sealed container or desiccant defeats the drying intervention. If a spool has been exposed to ambient air for more than 24 h at 50–60% RH, re-drying is required before a critical print. A hopper dryer with a dew point above −20 °C may leave the filament at 0.05 wt% moisture, which is outside the recommended envelope. Do not use a kitchen oven without closed-loop temperature control; local radiant over-temperature can deform the spool core or fuse adjacent strand turns.

Differences from other unfilled filament classes are summarized below. The values are representative ranges for natural-color PETG, general-purpose PLA, and general-purpose ABS; they are not lot-specific certificates for the Clariant product.

Compared with PLA, natural-color PETG has lower tensile yield strength but higher elongation at break and a higher heat deflection temperature. Compared with ABS, PETG has lower heat deflection temperature but can be printed at lower bed temperature and without styrene odor. The absence of styrene and the lower printed-bar deviation are primary reasons PETG is selected over ABS for open-frame printers. Compared with semi-crystalline PET, the glycol comonomer prevents the rapid crystallization that can cause warpage and interlayer opacity in PET printing.

Print-chamber Ventilation, Bed Adhesion, and Fan-speed Conflicts

An enclosed chamber is not mandatory for natural-color PETG. When chamber ambient temperature rises above 40 °C with the bed at 80 °C, thin vertical features may soften, and heat creep in an inadequately cooled hot-end throat can cause filament swelling and intermittent feed. A chamber temperature of 30–40 °C is usually sufficient for stress relief in structural prints. The part-cooling fan should not be disabled entirely for bridging: a fan speed of 20–30% after layer 2 reduces curl while preserving interlayer diffusion. On a glass bed coated with PVP, adhesion may be excessive; a release layer of water-soluble adhesive is recommended because PETG can pull glass chips from the build plate if the bed is not cooled to below 45 °C before part removal. On textured PEI, bed temperatures of 70–80 °C are sufficient; on bare glass, the upper end of the bed range is used with an adhesive interface. Spool-to-spool variation in melt flow can require a 5 °C bed adjustment when the fan speed remains constant.

Application contexts include transparent functional prototypes printed on open-frame fused filament fabrication machines, where the as-built material is expected to retain a tensile yield strength of 45–50 MPa and elongation at break of 15–25% under ISO 527-2. Electronics assembly fixtures and jigs are specified where the heat deflection temperature of 68–72 °C at 0.455 MPa under ISO 75-2/B defines the upper continuous-use boundary. Snap-fit enclosures require a minimum elongation at break above 10%; natural-color PETG typically satisfies this condition while PLA may not. The natural-color grade is also used for process qualification because the absence of colorants removes pigment-related nucleation and melt flow shifts. It is not an optical substitute for injection-molded PETG or polycarbonate; printed layer lines scatter light, and as-built haze is higher than a polished transparent molding. The material should not be specified for load-bearing food-contact articles or implant housings without written regulatory-grade evidence. For living-hinge applications, PETG is not equivalent to polypropylene; repeated flexing at a sharp notch can initiate stress cracking, especially when the print direction places layer boundaries perpendicular to the hinge axis.

Natural-Color PETG Does Not Automatically Inherit Food-Contact Status from Generic PET

The absence of carbon black or organic colorant is not proof of food-contact compliance. General-purpose unfilled PETG may contain stabilizers, catalysts, or process aids that are not evaluated under FDA 21 CFR 177.1630 or EU Regulation (EU) No 10/2011. For industrial use, documentation generally follows REACH Regulation (EC) No 1907/2006, Article 33 SVHC communication, and Directive 2011/65/EU as amended by (EU) 2015/863. The table below lists the usual compliance framework for general-purpose unfilled PETG filament; a lot-specific safety data sheet and certificate of conformance remain the controlling documents.

The operational envelope is defined by moisture, melt temperature, and bed temperature. Avoid blending the natural-color filament with amine-based colorants or additives not formulated for copolyesters because amine-functional species can accelerate ester cleavage at processing temperatures. If a print job is paused with the hot end held above 250 °C for more than 30 min, purge 20–30 mm of filament before resuming to remove heat-affected material. Natural-color PETG may adhere to polycarbonate build plates and can cause surface damage if part removal is forced before the bed cools to 45 °C. For bonded assemblies, solvent welding with methyl ethyl ketone or dichloromethane may be possible on annealed surfaces, but tensile shear data for this specific Clariant configuration is limited. When documented tensile impact, Charpy notched impact, or UV weathering performance is required, request a lot-specific external test report; generic PETG datasheets do not cover every printed geometry. The product should not be used in continuous service above the heat deflection temperature of 68–72 °C under 0.455 MPa load without a mechanical support strategy.