Envalior Novamid AM1030 FR (F) is an unfilled polyamide 6/66 filament grade formulated for fused filament fabrication. The grade carries a halogen-free flame-retardant package and is classified UL 94 V-0 at 1.5 mm and 3.0 mm thickness under the vertical burn method. The parenthesized F designation corresponds to the filament extrusion stream of the Novamid family and distinguishes the material from pellet-based injection-molding grades. Manufacturer-published typical data place melt temperature near 198 °C by ISO 11357-3 at 10 °C/min, density near 1140 kg/m³ by ISO 1183-1, and Vicat softening temperature near 196 °C by ISO 306 under 50 N and 50 °C/h. The mechanical property envelope quoted for dry specimens includes tensile modulus near 3100 MPa, yield stress near 66 MPa, and notched Charpy impact strength near 7.5 kJ/m² at 23 °C when tested according to ISO 527-1/-2 and ISO 179-1/1eA.

The choice of a PA6/66 copolymer rather than a PA66 homopolymer lowers the peak crystallization exotherm and reduces in-plane shrinkage that can produce lifting and Z-axis delamination in open-chamber machines. The same copolymer structure reduces heat deflection temperature compared with glass-filled PA66 fire-retardant compounds. The grade is therefore used in printed parts where fire performance is required but sustained structural load at elevated temperature is not the primary service condition. The base formulation contains no glass fiber, mineral filler, or carbon fiber; the unfilled nature preserves filament flexibility and reduces nozzle wear compared with reinforced flame-retardant materials. Printed tensile data are not equivalent to injection-molded data because raster anisotropy, void fraction, and interlayer contact are process variables.

How Does the Halogen-Free Phosphorus–Nitrogen System Attain UL 94 V-0 in a PA6/66 Matrix?

The flame-retardant chemistry operates through phosphorus-driven char formation in the condensed phase and nitrogen gas-phase dilution. During vertical burn testing, a coherent intumescent char layer forms at 1.5 mm and 3.0 mm thickness, preventing dripping and ignition of the cotton indicator. UL 94 V-0 requires total afterflame time no greater than 50 s across five specimens, no single afterflame time greater than 10 s, and no flaming drips. The limiting oxygen index of the dry compound is commonly reported near 32 % under ISO 4589-2. The char layer is thin and coherent; it does not show the glass-fiber wicking effect observed in reinforced systems in which reinforcement can transport fuel to the surface and disrupt intumescence. The product meets the halogen-free limits of IEC 61249-2-21, which sets bromine and chlorine thresholds at 900 ppm each and total halogen at 1500 ppm. Because the flame-retardant package is not brominated, combustion by-products are not dominated by the same brominated dioxin or furan profile; however, all engineering thermoplastics release toxic gases under fire, and fume extraction during processing and burning remains mandatory.

Before Printing, Condition the Filament as a Hydrolysis-Sensitive Melt

Conditioning of the filament follows a hydrolysis-controlled protocol. At 23 °C and 50 % RH, equilibrium moisture uptake is approximately 2.4 % according to ISO 62; saturation moisture content for the polyamide can exceed 9 %. Open spools are dried at 80 °C for 4 h to 12 h in a dry-air oven with dew point no higher than -30 °C. On production floors, filament is kept in a heated dry-box with dew point below -40 °C during long prints. Ambient relative humidity above 60 % can raise spool moisture above 0.15 % within 8 h. Wet filament produces visible surface foaming, poor layer fusion, and hydrolysis-induced molecular weight loss; these defects cannot be recovered by raising nozzle temperature. Dried spools should remain sealed until installed, and feed paths should minimize open-air residence time.

Melt Rheology and Extrusion Hardware Boundaries

The melt volume-flow rate of the grade is nominally 10 cm³/10 min at 260 °C and 2.16 kg per ISO 1133-1. This places the material in a viscosity range requiring a direct-drive or high-torque Bowden extruder with a hardened-steel or ruby orifice. Brass orifices can be used at the lower temperature boundary, but phosphorus-containing decomposition products accelerate surface oxidation of copper alloys at sustained 260 °C exposure. The standard extrusion range for 1.75 mm filament is 250 °C to 270 °C; 2.85 mm filament is processed near the upper end of the range when nozzle diameter exceeds 0.6 mm. Bed temperature is held at 100 °C to 110 °C for first-layer adhesion on PEI or PVA-coated glass, with chamber heating to 60 °C where available. All-metal hot ends are required because PTFE-lined hot ends degrade above 250 °C and cause unstable melt temperature. The practical nozzle-temperature window extends from approximately 245 °C to 280 °C. At temperatures above 280 °C, phosphorus-flame-retardant volatilization can create nozzle deposits; below 245 °C, insufficient melt thermal energy reduces interlayer diffusion. Long melt residence times above 30 min in a hot nozzle or heat break are avoided because phosphorus-based flame-retardant packages undergo thermal discoloration and may lose vertical burn performance.

Nominal Published Property Set for AM1030 FR (F)

Values are manufacturer-published typical data for the filament grade. They are not lot-release specification limits and do not represent printed-part properties at all orientations.

In printed-specimen testing under ISO/ASTM 52921, measured tensile modulus and strength vary with raster angle, extrusion multiplier, layer height, and layer time. XY-oriented specimens may diverge from the injection-molded values listed above by 15 % to 35 %. Z-oriented specimens generally exhibit lower tensile strength because interlayer diffusion is the controlling failure mechanism. Published data for Z-strength specific to this configuration are limited; process qualification therefore requires a build-orientation matrix on the same machine, nozzle size, and chamber temperature used for production.

When the Grade Replaces Unfilled PA6 or PA12 in Open-Chamber FFF Lines

Unfilled PA6 filament in the same application class commonly carries no V-0 rating and can drip under vertical burn, while AM1030 FR (F) forms a stable char at 1.5 mm and 3.0 mm. Compared with unfilled PA6, the flame-retardant package increases melt viscosity and reduces elongation at break. The tensile modulus remains similar to a typical PA6/66 base. In a direct comparison on the same open-platform FFF system, replacing PA6 filament with AM1030 FR (F) typically requires raising the extruder setpoint by 10 °C to 20 °C and increasing the first-layer bed temperature by 10 °C. The extrusion multiplier may require adjustment because melt density and die swell differ from unfilled PA6. Field data from open-platform systems indicate increased nozzle pressure with 0.4 mm nozzles; a 0.5 mm or 0.6 mm orifice reduces backpressure for long deposition runs without shifting XY tensile properties outside the same order as baseline PA6.

Compared with unfilled PA12, AM1030 FR (F) requires a higher bed temperature and more aggressive drying but provides a halogen-free V-0 option that unfilled PA12 without flame retardant cannot. The moisture regain is higher than PA12, and continuous immersion in hot water above 80 °C should be avoided because hydrolysis degrades the amide backbone. Relative to brominated flame-retardant PA66 compounds, the halogen-free chemistry avoids antimony trioxide and brominated flame-retardant listing concerns under IEC 61249-2-21. Halogen-free systems typically produce denser char and lower visible smoke density in standard laboratory observations, but published comparative smoke-density data for this specific compound are limited. Against carbon-fiber-filled print grades, the unfilled flame-retardant system is not electrically conductive and has lower stiffness; short carbon fiber increases tensile modulus but creates nozzle wear and can reduce surface resistance to flame spread by splitting the char layer.

The compliance matrix below summarizes resin-level declarations. These declarations do not cover pigments or additives introduced by masterbatch at the converter, and they do not replace certification of the printed article.

What Operational Boundaries Limit Long-Term Part Service?

The heat deflection temperature under 1.8 MPa is near 72 °C by ISO 75-2. Load-bearing printed parts should not operate above this value without creep testing, because the HDT method does not represent continuous stress at elevated temperature. Hydrolysis is the major chemical boundary: exposure to hot water, acids, or glycol-water mixtures above 60 °C reduces molecular weight and causes surface cracking. The grade is not recommended for continuous contact with strong acids or polyol-based brake fluids. Stress concentrations from holes, sharp radii, and support scars initiate interlayer cracks before bulk material yield; design radii should be maximized and supports removed before annealing. Annealing at 90 °C to 100 °C for 2 h can reduce residual stress but may alter flame-retardant exudation and dimensions; any annealed part must be re-evaluated for UL 94 classification at the final wall thickness.

Raw material UL 94 V-0 classification does not automatically transfer to end-product flammability certification. Final printed parts can differ by wall thickness, infill density, surface roughness, and flame exposure orientation. End-use certification requires testing the printed configuration in the final thickness and orientation. Combustion gases remain hazardous; thermal decomposition releases carbon monoxide, nitrogen oxides, and phosphorus-containing species, so fume extraction is required.