Clariant Natural Color High Impact Polystyrene 3D Printer Filament is a pre-compounded, unfilled, impact-modified styrene thermoplastic supplied for fused filament fabrication and material extrusion on open-architecture and enclosed platforms. The resin consists of a continuous polystyrene matrix with dispersed polybutadiene domains, commonly reported in the 0.5 µm to 5.0 µm range for extrusion grades; this two-phase structure converts crack propagation from brittle crazing to shear-yield deformation, yielding notched Charpy impact values of 8 kJ/m² to 15 kJ/m² under ISO 179-1/1eA at 23 °C. The natural-color designation means the compound is formulated without carbon black, titanium dioxide, or organic pigments, which removes particulate contrast agents that complicate solvent-support separation and optical dimensional verification. The filament is supplied in nominal diameters of 1.75 mm ± 0.05 mm and 2.85 mm ± 0.10 mm. Batch certificates typically report density of 1.03 g/cm³ to 1.06 g/cm³ by ISO 1183-1:2019 and melt flow rate of 4 g/10 min to 7 g/10 min at 200 °C with 5.00 kg using ISO 1133-1:2022. Published lot-specific data for this Clariant configuration are limited; the numerical ranges cited here are representative for unfilled high-impact polystyrene extrusion grades and should be checked against the spool label or batch certificate.

What separates this natural HIPS filament from pigmented ABS and conventional PLA support grades?

The primary differentiation is selective dissolution. Unlike PLA, which has no practical low-temperature solvent for fused-deposition support structures without attacking the part, HIPS can be removed by immersion in d-limonene at 30 °C to 40 °C. Polyvinyl alcohol and butanediol vinyl alcohol copolymer supports are water-soluble, but their equilibrium moisture uptake at 23 °C and 50 % RH is often 8 % to 12 % by weight, requiring sealed storage; HIPS absorbs approximately 0.1 % to 0.3 % under the same conditions when measured by ISO 62:2008. ABS shares hydrocarbon solvent sensitivity, but commercial ABS filament is almost always pigmented or compounded with processing aids that slow solvent penetration at the support-part interface. The natural HIPS grade also sits between ABS and PLA in tensile modulus: representative unfilled filament values are 1500 MPa to 2200 MPa for HIPS, 1900 MPa to 2600 MPa for ABS, and 3000 MPa to 3500 MPa for PLA, all measured according to ISO 527-2:2012 at 23 °C. The lower modulus reduces warping forces on large, flat layers, but the Vicat softening temperature of 85 °C to 100 °C under ISO 306/B50 is lower than many ABS grades and limits continuous service above 80 °C in load-bearing geometries.

In dual-extrusion use, this grade functions as a breakaway support for ABS and, to a lesser extent, for styrene-based terpolymers. Its value relative to acid-soluble or water-soluble support materials is that the support can remain dimensionally stable in a non-climate-controlled build room for longer periods than PVA or butanediol vinyl alcohol copolymer. Open spool exposure at 55 % RH and 23 °C for 24 h typically produces surface moisture below the threshold required to cause nozzle steam blistering, whereas PVA under the same condition may become unprintable. Micrographs of support-interface cross sections from dual-extruder parts printed with ABS reveal a sharp phase boundary when the HIPS layer is applied at 240 °C and the ABS layer at 250 °C. The absence of pigment reduces entrained solid particles at this boundary.

Drying is not optional when previously opened spools have been stored at ambient relative humidity above 60 %. A recirculating dehumidified air dryer at 70 °C for 4 h reduces moisture to an acceptable level; a convection oven without desiccant air exchange is less effective because the humidity inside the chamber is not swept away. Vacuum drying at 80 °C and −0.09 MPa for 2 h is suitable for lot sizes under 1 kg. Hot-end oozing, diameter expansion at the nozzle, and surface splay on the first layer are field indicators that moisture has exceeded 0.1 % by weight. If the first layer is printed on a borosilicate glass plate with a polycarbonate adhesion film, the bed temperature should be 100 °C to 110 °C for the first three layers and 90 °C to 100 °C thereafter. Build-chamber air temperature should be kept at 40 °C to 60 °C for parts with long straight walls longer than 150 mm. An enclosure is required below 35 °C ambient temperature to prevent corner delamination; a polycarbonate or polypropylene enclosure panel reduces drafts but does not replace a heated chamber. Bed adhesion can be enhanced with a thin styrene-acrylonitrile copolymer film or high-temperature polyester tape; silicone release agents are not recommended because migration to the part surface interferes with d-limonene wetting during support removal.

The linear coefficient of thermal expansion for unfilled HIPS is typically 8 × 10⁻⁵ K⁻¹ to 2 × 10⁻⁴ K⁻¹ between 23 °C and 80 °C under ISO 11359-2:2021. This value is higher than many ABS grades in the print direction and explains why large flat parts require an actively heated chamber or high-temperature bed on open machines.

Dimensional tolerance, batch-certified physical property ranges, and extrusion melt stability

Inline two-axis laser micrometers operating at 1 m/min to 3 m/min measure diameter and ovality. The production specification for the 1.75 mm filament is a maximum ovality of 0.03 mm; for 2.85 mm, maximum ovality is 0.05 mm. Spool winding tension is maintained at 1.5 N to 3.0 N to prevent interlayer stretching and self-overlap binding. Batch-release testing includes melt flow rate under ISO 1133-1:2022, density under ISO 1183-1:2019, tensile yield and modulus under ISO 527-2:2012, and notched Charpy impact under ISO 179-1/1eA. A batch is non-conforming if moisture after 24 h water immersion at 23 °C exceeds 0.15 % by weight, as that indicates microvoids or surface contamination that will cause nozzle outgassing.

On the melt-processing side, polybutadiene domain coalescence is the critical degradation mode. In twin-screw compounding trials using a co-rotating 40:1 L/D extruder with vacuum devolatilization at −0.08 MPa, melt temperatures above 240 °C for residence times exceeding 90 s produced a reduction of notched Charpy impact from 12 kJ/m² to 7 kJ/m² in subsequent injection-moulded test specimens. Fused-filament printers should therefore limit nozzle setpoint to 220 °C to 245 °C and keep the heat-break cooling fan at the manufacturer-specified speed. Direct-drive extruders with hardened steel gears are preferred for the 2.85 mm diameter because the lower melt-flow grade creates feed-roll slip on poorly tensioned Bowden tubes.

Mixing of this grade is not performed by the end user.

The comparative data in the table are not a substitute for lot-specific batch certificates. The Clariant natural HIPS grade is typically selected when the part requires low moisture sensitivity, hydrocarbon-solvent support removal, or translucent dimensional-reference features. It is not selected when tensile yield strength above 30 MPa or continuous service above 80 °C is required.

When d-limonene exposure is used for sacrificial support removal

Support dissolution follows a mass-transfer-limited process that depends on solvent temperature, support wall thickness, and agitation. At 30 °C, a solid HIPS support block 10 mm thick may require 8 h to 12 h to soften; the same volume in an ultrasonic bath operating at 40 kHz to 80 kHz and 35 °C softens within 2 h to 4 h. Thin support walls below 0.8 mm dissolve first, while enclosed cavities and blind holes retain a gel layer of swollen HIPS. Mechanical removal of the gel is performed with brass or acrylic scrapers; steel tools can score the ABS part surface. d-Limonene is a skin and respiratory irritant; extraction should be performed under local exhaust ventilation with nitrile gloves and polycarbonate splash goggles. The solvent should not be heated above 45 °C because oxidation products can deposit on the part. Post-dissolution rinsing with isopropanol or ethyl alcohol at 20 °C to 25 °C removes residual terpene oils before sanding or priming.

Thermal aging shifts the lower-bound notched impact resistance of unpigmented HIPS prints

Unpigmented HIPS is not an outdoor or high-temperature material. Continuous exposure to air at 70 °C for 500 h can embrittle the polybutadiene phase, reducing notched Charpy impact from 12 kJ/m² to below 6 kJ/m² in unconditioned specimens. UV exposure causes yellowing and surface crazing within 200 h to 400 h under ASTM D4329-13 cycle A or equivalent xenon arc conditions; a clear acrylic lacquer can slow this but is not a substitute for a styrene-acrylonitrile shell. The material is attacked by aromatic hydrocarbons, chlorinated solvents, ketones, and gasoline; it is resistant to aqueous acids and bases only at low concentrations and low temperatures. Stress-cracking can occur when a printed part is bolted to a metal fixture while solvent residue is present. Users should pre-drill holes with 0.1 mm to 0.2 mm clearance to reduce clamping stress.

A compliance checklist matrix is provided below for regulatory and test-standard traceability.

The natural HIPS filament should be stored in a sealed moisture-barrier pouch with silica gel or molecular sieve desiccant at 15 °C to 25 °C. Once opened, the spool should be returned to the pouch within 8 h if ambient relative humidity exceeds 60 %. The grade is not suitable for direct food-contact applications unless migration testing under Regulation (EU) No 10/2011 has been completed for the specific printed shape. Flammability is classified at HB under UL 94 for thicknesses 1.5 mm and 3.0 mm; this is not a V-0 or V-2 rated material. REACH and RoHS compliance for the natural color compound should be confirmed by supplier declaration; the absence of heavy-metal pigments and brominated flame retardants is consistent with the natural high-impact polystyrene compound, but processing aids and mineral oil residues may be present at levels below regulatory thresholds. For industrial users with ISO 13485 or IATF 16949 quality systems, the batch certificate should be retained for traceability. Published data for this specific Clariant configuration are limited, and the numerical values in this document are representative engineering data for unfilled high-impact polystyrene extrusion grades rather than a substitute for the manufacturer’s lot-specific datasheet.