BASF 3D Ultrafuse PAHT CF15 Fused Filament, Conditioned is a short-carbon-fiber-reinforced high-temperature polyamide compound produced for material extrusion. The product contains **15 wt%** carbon fiber in a semi-aromatic polyamide matrix. It is supplied in **1.75 mm** and **2.85 mm** nominal diameters with a standard spool mass of **750 g**. The conditioned designation refers to the moisture-controlled packaging in which the filament is shipped: desiccant-loaded barrier film, heat-sealed closure, and an internal atmosphere kept below the threshold at which absorbed water would flash to steam during extrusion. Solid density is specified as **1.15 g/cm³** under **ISO 1183-1**. The melt-zone temperature recommended by the supplier is **270 °C to 300 °C**, while the heated build surface is set between **90 °C and 120 °C**. These parameters place the material in a higher thermal class than unfilled PA6 and many PA12-based carbon-filled filaments.

The semi-aromatic polyamide backbone provides elevated heat deflection response, while the **15 wt%** carbon fiber reduces in-plane shrinkage and raises modulus. Mechanically, printed coupons tested in the XY orientation under **ISO 527-2** typically fall between **80 MPa and 90 MPa** tensile strength, **4.0 GPa and 5.0 GPa** tensile modulus, and elongation at break below **5 %**. Flexural modulus under **ISO 178** exceeds tensile modulus because the flexural fixture constrains the compressive face. Heat deflection temperature under **ISO 75-2** at **1.8 MPa** is reported above **130 °C**; method B at **0.45 MPa** is reported above **140 °C** for printed test coupons. These values are not isotropic. Z-direction tensile strength and interlayer bond strength are lower than XY values and are strongly influenced by chamber temperature, layer time, and raster offset.

What is the Practical Significance of the Conditioned Designation in Fused Filament Fabrication?

The conditioned packaging controls the initial moisture state of the filament at the moment of extrusion. Polyamide absorbs water through reversible hydrogen bonding at the amide groups. If a spool equilibrates with ambient air above **60 % RH**, the absorbed water enters the heated melt zone and volatilizes, producing steam that disrupts the melt bead. The resulting failure modes include intermittent foaming, nozzle drool, poor first-layer adhesion, reduced melt viscosity, and surface pits on the printed wall. Drying before processing is therefore mandatory after prolonged exposure. The supplier-specified drying regime for this product is **80 °C** for **8 h** in a forced-air convection oven with a dew point below **-30 °C**. A shorter alternative of **100 °C** for **4 h** may be used when the spool has been exposed to ambient air for fewer than **12 h**. Over-drying above **120 °C** is not recommended because oxidative embrittlement of the polyamide matrix and spool deformation can occur.

Moisture uptake after printing is a separate phenomenon from filament conditioning. Test coupons should be conditioned under **ISO 291** or **ASTM D618** at **23 °C/50 % RH** until mass equilibrium before reporting mechanical properties. In the dry as-printed state, tensile modulus and tensile strength are higher, while elongation at break and impact energy absorption are lower. After moisture conditioning, water molecules penetrate the amorphous regions and disrupt interchain hydrogen bonds, reducing the glass-transition temperature and increasing chain mobility. The resulting property shift is reversible but not negligible. For carbon-filled polyamide, the fiber-matrix interphase can act as a capillary path, so moisture ingress in a printed coupon may be faster than in the unfilled matrix despite the hydrophobic nature of the carbon fiber itself. Published data for the exact moisture diffusion rate through printed PAHT CF15 under **ISO 62** is limited; however, weight gain after **40 h** at **23 °C/50 % RH** can fall in the range of **1.0 wt% to 2.0 wt%**, depending on void content and infill density.

Moisture also changes rheology. A polyamide conditioned to **0.15 wt% to 0.25 wt%** moisture has a measurably higher melt volume rate than the same resin dried below **0.05 wt%**. The viscosity shift changes die swell, layer squash, and the tendency to stretch molten filament across concave radii. On production-scale direct-drive systems equipped with hardened steel **0.6 mm** nozzles, batch-to-batch differences in fiber length distribution can alter hot-end pressure drop by as much as **10 % to 20 %**, even when the nominal carbon fiber content remains **15 wt%**. This variation originates in the compounding step, where twin-screw extruders with L/D ratios between **40:1** and **48:1** are used to side-feed carbon fiber downstream of the polymer melting zone. Side-feeding limits fiber attrition and preserves aspect ratio, but it also introduces lot-to-lot variability in fiber length and dispersion. These differences are not captured by a simple carbon content specification.

Nozzle Abrasion, Extrusion Temperatures, and Chamber Thermal Requirements

Carbon fiber at **15 wt%** is sufficiently abrasive to exclude brass and aluminum-bronze nozzles from production use. Orifice wear becomes measurable within the first kilogram of throughput and widens the nozzle bore, producing over-extrusion in thin wall sections and a loss of toolpath accuracy. Hardened tool steel, silicon carbide, or ruby nozzle orifices of **0.6 mm** minimum are specified. A **0.8 mm** orifice is preferred for long-duration runs because the larger bore reduces residence time and lowers the probability of fiber-bundle clogging at the orifice entry. Nozzle wear beyond **0.05 mm** in bore diameter is enough to alter extrusion width and should trigger nozzle replacement in dimensionally critical parts. Layer height is typically maintained between **0.15 mm and 0.25 mm** with a **0.6 mm** nozzle, keeping the layer height below **0.4** of the nozzle diameter to maintain interlayer pressure.

Heated chamber control is a critical boundary for this material. The part must remain above the matrix recrystallization temperature during deposition so that the frozen skin of the previous layer can fuse to the new layer. A chamber temperature of **50 °C to 80 °C** is specified depending on part wall thickness and overall build height. Below **50 °C**, differential shrinkage between the upper and lower regions of a thick wall creates interlayer tensile stress that may exceed the Z-direction bond strength, leading to delamination. Above **80 °C**, over-softening of the part can cause slumping in tall components, especially in low-infill sections. The build plate is held at **90 °C to 120 °C**, with the upper range used during the first layers and the lower range used once the chamber reaches steady state. A recirculating heated chamber is preferred over an open Cartesian frame because carbon-filled polyamide has higher thermal conductivity than unfilled PA6, drawing heat away from the extrudate more rapidly. This rapid heat loss can create non-uniform crystallinity across layer boundaries and is a common source of warping in reinforced polyamides.

Volumetric flow should be maintained between **2.0 mm³/s and 6.0 mm³/s**. Above **6.0 mm³/s**, the filled melt exhibits melt fracture and surface sharkskin because the carbon-filled melt has a higher storage modulus and shorter stress relaxation time than the unfilled matrix. Below **2.0 mm³/s**, residence time in the nozzle becomes excessive and thermal degradation of the antioxidant package may occur, visible as yellowing or a reduction in interlayer toughness. The following table summarizes the main processing window for the conditioned filament.

The material is routinely processed on hard-tool dual-extrusion systems where a water-soluble support is not used. Support structures, when required, are printed from a breakaway or thermally stable support material capable of surviving the chamber temperature range. Soluble support materials based on polyvinyl alcohol are not suitable because the chamber temperature can exceed the softening point of the support, causing bond failure and dimensional drift. In addition, the carbon-filled surface is more abrasive to drive wheels and guide tubes than unfilled polyamide; frequent inspection of extruder drive gears for fiber-filled polymer dust is a standard maintenance practice on high-throughput equipment.

Printed components made from PAHT CF15 are used for short-run manufacturing fixtures, robotic end-effectors, inspection gauges, welding jigs, and functional brackets exposed to elevated temperature. The heat deflection temperature above **130 °C** under **ISO 75-2** at **1.8 MPa** supports short-term exposure in under-hood and machine-tool environments. However, continuous load-bearing use above the heat deflection temperature is outside the product’s mechanical boundary unless creep-rupture data under **ISO 899-1** are generated for the specific printed density, wall count, and orientation. For applications involving contact with hydrocarbons, brake fluid, or glycol-based coolants, immersion testing under **ISO 175** is required because polyamide chemical resistance is environment-specific and the carbon fiber may create additional wicking paths into the laminate.

In comparison with an unfilled PA6, the carbon fiber reduces in-plane coefficient of thermal expansion and raises stiffness while reducing fracture toughness. Unfilled PA6 can exhibit elongation at break above **20 %** in the XY orientation, whereas the **15 wt%** carbon-filled PAHT remains quasi-brittle with elongation values below **5 %**. This is a design boundary: unfilled PA6 absorbs more impact energy under **ISO 179-1eU**, but PAHT CF15 retains a larger fraction of its storage modulus at elevated temperature. Compared with a PA12-based carbon-filled grade, PAHT CF15 typically provides higher heat deflection temperature and higher tensile strength, while PA12 CF offers lower moisture uptake and improved chemical resistance in certain hydrocarbon environments. The selection is governed by the temperature-humidity regime and the tolerance for anisotropic shrinkage during printing, not by a single strength ranking.

When Carbon Fiber Loading Reaches 15 wt% Relative to Unfilled or Glass-Filled Polyamide

The use of **15 wt%** carbon fiber rather than higher loadings creates a specific processing boundary. At higher carbon fiber content, the interlayer bond strength declines because fiber ends concentrate at raster boundaries and reduce the available polymer-to-polymer welding area. The **15 wt%** level leaves enough matrix resin to maintain interlayer fusion while still increasing stiffness and reducing warpage relative to an unfilled semi-aromatic polyamide. Glass-fiber-filled polyamide may offer similar stiffness at lower cost, but carbon fiber provides a higher stiffness-to-density ratio and modifies the thermal conductivity of the printed laminate. The carbon fiber also lowers surface resistivity compared with neat polyamide, although the product is not classified as an electrically conductive filament and published data for printed surface resistivity of PAHT CF15 is limited.

Reinforcement changes moisture equilibrium in a way that is not captured by a simple rule of mixtures. Carbon fiber itself is hydrophobic and does not absorb water, but the fiber-matrix interphase can generate microvoids and capillary paths within the printed solid. Consequently, the measured moisture uptake under **ISO 62** at **23 °C/50 % RH** in a printed PAHT CF15 coupon may be lower than the unfilled matrix at equilibrium but faster in the early absorption phase. The lower equilibrium moisture content has a practical consequence: the drop in tensile modulus from dry to conditioned state is smaller in PAHT CF15 than in an unfilled polyamide of the same amide group density. This improves dimensional repeatability for parts that operate in fluctuating ambient humidity but does not eliminate the need to dry the filament before extrusion.

The product is not a direct substitute for continuous-fiber-reinforced engineered plastics in primary structural components. Its performance envelope is defined by the material extrusion process, the printed wall count, and the layer-bond microstructure. Components with sharp corners, thick-to-thin transitions, or large flat sections require evaluation of residual stress and warpage before full-scale production. Published data for PAHT CF15 under combined thermal and hygrothermal aging is limited, so applications involving long-term exposure to both heat and moisture should be validated against **ISO 527-2**, **ISO 75-2**, and **ISO 179-1eU** on printed coupons representative of the final build orientation.