Ensinger TECAFIL PEEK VX CF30 black is a 1.75 mm nominal-diameter fused filament fabrication feedstock in which polyetheretherketone is compounded with a nominal 30 wt% carbon fiber reinforcement. The designation distinguishes the material from unfilled TECAFIL PEEK VX black and from glass fiber reinforced PEEK grades. The black color is a consequence of the carbon fiber fraction, not a separate pigment addition. Under ISO 1183-1, the filled material is typically specified in the density range 1.39 g/cm³ to 1.42 g/cm³, compared with 1.30 g/cm³ to 1.32 g/cm³ for unfilled polyetheretherketone. The PEEK matrix retains a glass transition near 143 °C and a crystallite melting point near 343 °C; however, the mechanical response of a printed part depends on the crystalline fraction developed during deposition and on any subsequent annealing.

The product is supplied in 1.75 mm format for high-temperature direct-drive extrusion systems. Lot-specific certificates should be consulted for diameter tolerance, ovality, and roundness because carbon fiber loading influences die swell during filament extrusion. Vacuum-sealed spools with desiccant are standard for storage; once opened, the filament should be maintained below 10% relative humidity or dried before processing. The filament is intended for fused filament fabrication systems with actively heated chambers and hardened extrusion hardware; unheated or PTFE-lined hot ends are outside the operating envelope.

What limits interlayer fusion when the chamber remains below 120 °C?

Interlayer fusion in carbon fiber reinforced PEEK is controlled by the thermal history of the previously deposited road surface. PEEK crystallizes slowly; if the chamber and build surface are held below 120 °C, the deposited road may cool into an amorphous or low-crystallinity condition before the next layer is applied. The carbon fiber fraction increases melt viscosity and restricts bulk flow at the road-to-road interface, so low chamber temperature produces elongated microvoids and low molecular interdiffusion. In this condition, tensile strength perpendicular to the build direction has been reported below 50% of the in-plane ultimate tensile strength in printed coupons tested according to ISO 527-2. Heated-chamber systems maintained at 140 °C to 180 °C reduce the cooling rate, permit crystallization to proceed, and improve interlayer consolidation. Chambers that cannot reach 120 °C are not recommended for structural parts made from this material because the interlayer boundary becomes the dominant failure location.

Predrying is mandatory before extrusion. The spool should be dried at 120 °C for 6 h in a vacuum oven or at 150 °C for 4 h in a circulating-air oven with a dew point below -20 °C. Residual moisture above 0.02 wt% generates steam at the nozzle and produces surface porosity, dimensional variation, and reduced interlayer fracture toughness. Drying above 180 °C is not recommended because oxidative degradation of the PEEK matrix can alter melt viscosity and narrow the process window. After drying, the spool should be held at 10% relative humidity or lower during printing; otherwise, moisture re-adsorption occurs within hours at ambient humidity.

At processing temperatures above 390 °C, moisture is not the only volatile risk. Carbon fiber ends may accelerate oxidative degradation at the surface, and excessive residence time at 430 °C or above can produce dark discoloration, increased nozzle pressure, and reduced melt strength. The practical processing window is therefore narrower than for unfilled PEEK. For long-duration builds, the hot end should be purged according to the supplier's residence-time recommendation, and the print schedule should be structured to avoid prolonged idle heating.

Comparative property envelope for unfilled PEEK, PEEK GF30, and PEEK VX CF30

Table 1 lists representative published property ranges for 30 wt% carbon fiber reinforced PEEK, 30 wt% glass fiber reinforced PEEK, and unfilled PEEK. The values are not a specification for any specific spool; they are initial screening ranges. Final design allowables should be derived from printed-coupon testing because layer orientation, chamber temperature, and post-annealing change the mechanical response.

The carbon fiber grade differs from glass fiber filled PEEK in electrical and thermal behavior. Under ASTM D257, glass fiber filled PEEK remains insulative, while carbon fiber filled PEEK may fall into the static-dissipative range with surface resistivity below 10⁶ Ω/sq. The carbon fiber grade also has higher thermal conductivity, which reduces thermal gradients in the deposited layer but increases heat loss to the chamber air. These differences make carbon fiber filled PEEK more suitable for fixtures that must not accumulate static charge, but less suitable for electrical isolation components unless post-coated or verified for dielectric strength.

When the spool is transferred to a direct-drive high-temperature print head

Processing requires hardware rated for continuous operation at 400 °C. The nozzle must be constructed from hardened tool steel, stainless steel with a hardened insert, or ruby/diamond-coated brass; uncoated brass, aluminum, and standard PTFE-lined hot ends are not acceptable. The carbon fiber reinforcement produces abrasive wear on the nozzle orifice, feed path, and drive gears. A minimum orifice diameter of 0.40 mm is recommended because the 30 wt% fiber loading increases the risk of clogging below this diameter. Extrusion temperatures are typically set between 390 °C and 430 °C, with the exact setpoint adjusted for thermocouple offset, print speed, and layer height. The build plate is held at 150 °C to 180 °C, and an actively heated chamber is maintained above 120 °C, preferably between 140 °C and 180 °C, to prevent warpage and delamination. Print speeds are usually limited to 20 mm/s to 50 mm/s depending on extrusion geometry because the melt viscosity of carbon fiber filled PEEK is higher than unfilled PEEK. Layer heights from 0.15 mm to 0.25 mm are common; layer heights below 0.10 mm increase shear rate and may not be practical.

The higher apparent viscosity of carbon fiber filled PEEK affects pressure drop in the hot end. Typical melt volume-flow rate tested according to ISO 1133-1 at 380 °C with 5 kg may lie between 2 cm³/10 min and 8 cm³/10 min for this filler loading, whereas unfilled PEEK commonly falls above 10 cm³/10 min. The exact value depends on fiber length distribution and compounding history. A direct-drive extruder with a high-torque stepper motor and a short, constrained filament path is required; Bowden systems are not recommended. The cold-end heat sink must keep the feed zone below 60 °C to prevent premature softening and buckling. The part-cooling fan is normally disabled because localized air flow below 120 °C chamber temperature causes skin formation and delamination.

On borosilicate glass, carbon fiber filled PEEK does not adhere reliably unless the build surface is treated. High-temperature polymer films based on polyetherimide or PEEK, or coated aluminum substrates, are used with a build plate temperature of 150–180 °C. The first layer should be deposited at 10–20 mm/s with a layer height of 0.20 mm and no part-cooling fan. If the chamber is below 120 °C, the first layer may release during the build because the differential contraction between the solidified PEEK and the build plate exceeds the available adhesion.

After deposition, annealing is performed at 200 °C to 220 °C for 2 h to 4 h in a circulating-air oven. The part should be fixtured because stress relaxation can produce distortion in thin walls. Annealing increases crystallinity, raises heat deflection temperature, and reduces residual stress, but it can also cause dimensional changes of up to 0.2–0.5% depending on toolpath and fiber orientation. For parts requiring tight tolerances, post-annealing machining is recommended.

The filled material exhibits a lower coefficient of linear thermal expansion than unfilled PEEK, typically 15–25 ppm/K below the glass transition, which reduces warpage during heated builds and improves dimensional stability in fixtures exposed to 20 °C to 250 °C service conditions. The same carbon fiber fraction reduces elongation at break to approximately 1.5–2.5%; snap-fit and high-strain elements that depend on ductile yield are outside the material’s operational boundary. The printed surface has a matte black appearance and may show fiber ends at road boundaries. If the part is used as a bearing or wear surface, published pin-on-disc data for compression molded carbon fiber reinforced PEEK show reduced specific wear rate against hardened steel counterfaces compared with unfilled PEEK, but published data for fused filament fabrication coupons of this exact Ensinger grade are limited and should be generated before use in a qualified wear application.

Candidate production applications include high-temperature assembly fixtures, inspection gauges, static-dissipative handling equipment, and mechanical test fixtures exposed to repeated thermal cycling. The material is also used for short-run functional prototypes of compression molded or machined PEEK components when an isotropic molded blank is not available. In all cases, the anisotropy introduced by fused filament fabrication must be accounted for in the design; the carbon fiber orientation follows the toolpath and produces higher in-plane stiffness than through-thickness stiffness.

Chemical resistance follows the PEEK matrix; the grade is resistant to hot water, steam, many acids, bases, and non-halogenated organic solvents. Concentrated sulfuric acid, concentrated nitric acid, and some halogenated hydrocarbons can attack the matrix at elevated temperature. The carbon fiber filler may also participate in galvanic reactions when placed against dissimilar metals in humid electrochemical environments; printed parts intended for such service should be tested under the actual electrolyte and potential. Compliance with RoHS 2011/65/EU and REACH 1907/2006/EC is evaluated by the filament supplier on a lot-specific basis; carbon fiber reinforcement does not normally introduce heavy metals, but the finished filament article status may depend on the importer and the specific substance list. Food-contact and medical use are not assumed for this carbon fiber filled product. Published data for this exact configuration under FDA 21 CFR 177.2415 or ISO 10993-1 are limited, and end-use migration or biocompatibility testing is required before those applications.