Covestro Addigy FPB 2684 000000 A is a flame-retardant polycarbonate/acrylonitrile-butadiene-styrene blend supplied as fused filament fabrication feedstock. The 000000 A suffix identifies the standard black color and additive package. The grade is positioned for additively manufactured components that require a combination of UL 94 V-0 classification at 1.5 mm wall thickness, higher heat resistance than unfilled ABS, and lower warpage than neat polycarbonate. Filament is available in nominal diameters of 1.75 mm and 2.85 mm; lot-specific diameter and ovality data should be obtained because deviations greater than ±0.05 mm alter volumetric flow prediction in direct-drive and Bowden toolheads. Density is approximately 1.17 g/cm³ by ISO 1183-1. Supplier technical literature reports a tensile modulus of 2300 MPa and a tensile stress at yield of 51 MPa by ISO 527-2. The nominal strain at break exceeds 50% under the same standard, distinguishing the product from stiff, brittle flame-retardant ABS compounds. Vicat softening temperature B50 is approximately 105 °C by ISO 306, and heat deflection temperature at 1.8 MPa is approximately 92 °C by ISO 75-2. The product is intended for FFF systems with an actively heated build plate and preferably a closed, ventilated build chamber.

The values in Table 1 are typical lot averages and are not specification limits; FFF process parameters, part density, raster orientation, and annealing history shift final part properties. Printed Z-direction tensile strength is lower than in-plane values and must be characterized with printed coupons rather than molded plaques or filament data.

Because the PC phase undergoes hydrolysis at melt temperature, moisture content above 0.03 wt% reacts with carbonate linkages during extrusion above 260 °C, reducing molecular weight and producing splay, nozzle pressure instability, and weak interlayer fusion. The established drying protocol is 80 °C for 4 h in dehumidified air with a dew point below -30 °C. Spools left unprotected at 23 °C and 50 % RH for more than 2 h should be re-dried before printing. In long prints, the spool should remain in a sealed dry box because PC/ABS filament regains surface moisture rapidly; a passive desiccant chamber is insufficient if ambient absolute humidity exceeds 10 g/m³. Lot-to-lot variation in filament diameter and moisture content remains a practical bottleneck in production. Users running high-volume print farms should log filament diameter with a two-axis laser micrometer and adjust the extrusion multiplier per lot; a diameter shift from 1.75 mm to 1.70 mm changes the cross-sectional area by approximately 6%, which is sufficient to produce under-extrusion porosity in pressure-tight parts. Spools should be weighed before and after drying; mass loss above 0.1 wt% after 80 °C drying indicates free surface moisture rather than deep resin moisture, and the drying cycle should be extended only if a moisture analyzer still indicates unacceptable residual water.

Processing Window, Heater Setpoints, and the Consequences of Overshoot

Nozzle setpoints for FPB 2684 are typically 270–290 °C, with build plate temperatures between 100 °C and 120 °C. The closed-chamber air temperature should not exceed 60 °C unless the part is self-supporting or printed with removable support because the ABS phase loses modulus above that threshold, leading to overhang sag. Print speeds of 30–60 mm/s are used with 0.4 mm nozzles; larger 0.6 mm and 0.8 mm hardened steel nozzles can operate at the upper end of the speed range but require a proportional increase in extrusion temperature to maintain melt flow. The flame-retardant package increases melt viscosity relative to unfilled ABS; filament grinding during high-speed infill is common when the idler tension is set too high. Use of hardened steel or ruby nozzle assemblies is recommended because the flame-retardant additive system may accelerate brass nozzle wear over runs longer than 250 h. Retraction distance for direct-drive toolheads is normally 0.8–1.5 mm; Bowden systems longer than 400 mm may require 4–6 mm but should be optimized because excessive retraction creates voids at seam locations.

Build plate preparation uses a PEI film, a PC/ABS-compatible adhesive, or a heated glass bed with a dedicated bond layer; painter’s tape is generally unsuitable because the bed temperature exceeds 100 °C and adhesive breakdown causes localized lifting. A brim or raft is recommended for parts with sharp corners and continuous flat spans longer than 100 mm to distribute shrinkage stress. Print acceleration and jerk settings should be reduced on large flat parts because abrupt direction changes at the perimeter can amplify edge stress and initiate delamination before the first layer has cooled below the glass transition range.

Large-frame production machines with 0.8 mm hardened steel nozzles and actively heated chambers typically operate at the upper end of the temperature range because the higher volumetric flow rate shortens polymer residence time. Process logs from production printing of PC/ABS show that melt-pressure fluctuation below ±0.3 MPa is a useful control boundary; larger fluctuations correlate with moisture, partial nozzle clogging, or filament diameter drift. If the hot-end pressure signal exceeds this window while the measured filament diameter remains within tolerance, the build should be paused because continued extrusion can deposit degraded material in the part.

The primary difference from unfilled ABS filament is the retention of UL 94 V-0 at 1.5 mm after printing; unfilled ABS typically occupies UL 94 HB. Compared with neat polycarbonate filament, FPB 2684 has lower heat deflection temperature but substantially lower shrinkage stress. Neat PC often requires chamber air temperatures above 80 °C and build plate temperatures near 120 °C to suppress delamination on large flat sections, whereas FPB 2684 prints at chamber air temperatures of 40–60 °C with fewer edge-lift failures. Compared with mineral-filled or glass-filled flame-retardant PC/ABS compounds, this grade retains a nominal strain at break above 50%, which is advantageous in snap-fit geometries and impact-loaded housings. The trade-off is lower stiffness; parts requiring flexural modulus above 4000 MPa should be evaluated against filled grades rather than FPB 2684. Within the Covestro Addigy portfolio, FPB 2684 is positioned as a flame-retardant PC/ABS, whereas neat PC filament grades have higher heat resistance but require more aggressive chamber heating. The product is not a general-purpose ABS replacement because drying is mandatory and nozzle temperatures are higher, but it is a lower-warpage alternative to neat PC for medium-size electrical housings where UL 94 V-0 is required.

What Limits the Use of FPB 2684 in Live-Edge Electrical Applications?

Flame-retardant PC/ABS grades are specified for power-supply housings, electrical enclosures, and battery-management brackets because they combine fire resistance with moderate toughness. For FPB 2684, the UL 94 V-0 classification at 1.5 mm is a small-scale vertical burn test result; it does not automatically confer compliance with IEC 60695-2-12 glow-wire end-product requirements or IEC 62368-1 for information technology equipment. Printed wall thickness, shell count, infill density, and layer orientation all shift flammability behavior relative to the supplier’s molded or printed test specimens. For printed electrical enclosures, clearances and creepage distances must be validated on printed coupons under IEC 60664-1; interlayer voids may reduce dielectric withstand and create partial discharge paths. Published data for the comparative tracking index of FPB 2684 under IEC 60112 is limited, so printed CTI must be measured rather than assumed from molded PC/ABS literature. The compound is not recommended for direct contact with ketones, chlorinated solvents, strong aqueous alkali, or aromatic hydrocarbons; the PC phase is susceptible to environmental stress cracking under constrained load, and surface crazing may appear before mechanical failure.

Primary use cases are printed non-structural electrical housings, enclosures with limited mechanical load, wire guides, battery-management brackets, and interior transportation clips where flame retardancy and moderate heat resistance are required. For structural end-use parts, printed coupon testing under ISO 527-2 and ISO 179-1eA is required because FFF part strength is anisotropic and depends on raster orientation. In pressure-containing components, the product has not been qualified under pressure vessel standards; published data for this specific configuration is limited.

Where the Processing Window Narrows: ABS-Phase Degradation and Interlayer Fusion

At nozzle setpoints above 300 °C, residence time becomes critical because the butadiene phase and the flame-retardant package degrade in parallel. The degradation signature is a color shift from black toward brown, increased melt-pressure oscillation, and a sharp styrenic odor. Melt residence time in the hot end should be kept below 5 min during pauses; idling at 280 °C for more than 10 min can form carbonaceous deposits that intermittently clog 0.4 mm nozzles. Interlayer fusion strength in FFF PC/ABS is controlled by polymer diffusion at the road interface; part strength in the Z direction is lower than in-plane and typically falls to 40–65% of the XY value depending on nozzle temperature, layer height, and chamber air temperature. For load-bearing brackets, a layer height below 0.2 mm and a chamber air temperature of 40–60 °C are used to extend contact time and reduce premature quench. Production-scale large-format printing with 0.8 mm nozzles has shown that extrusion multipliers above 1.0 are often needed to fill interlayer voids, but overextrusion above 1.15 produces nozzle plowing and surface roughness.

In service, the PC phase provides dimensional stability and impact resistance; the ABS phase contributes processability and lowers notch sensitivity compared with neat PC in some geometries, but low-temperature impact is less forgiving. Components required to meet low-temperature impact specifications should be tested by ISO 179-1eA at the actual service temperature because published Charpy notched impact data for FPB 2684 are generally reported at 23 °C. Annealing is possible only below 95 °C; higher temperatures distort thin walls and relieve stresses unevenly. The material is supplied in black under the 000000 A code; alternative colors should be specified through separate material codes. Filament should be stored in sealed containers with desiccant after opening, and partially used spools should not be left on open machine mounts in humid production rooms for more than one shift.