PAHT-CF High-temperature carbon-fiber nylon (QIDI PAHT-CF, also sold as PPA-CF)

PAHT-CF is a high-temperature nylon reinforced with chopped carbon fiber. QIDI sells it under both names, PAHT-CF and PPA-CF, and describes the base as a semi-aromatic polyamide. PPA, polyphthalamide, has stiff ring structures in its backbone that raise heat resistance and stiffness and cut water uptake compared with ordinary nylon. QIDI says its base absorbs about one tenth the moisture of PA6 at saturation.

It is among the strongest and most heat-resistant materials we print. As printed, it's stiff and strong but handles heat only a little better than PETG. Once annealed, the heat resistance at light load more than doubles, which is what puts it in a different league. QIDI's blog notes other brands use both labels for different formulations, so a datasheet from another supplier may not match.

PAHT-CF is abrasive, needs a hardened nozzle of 0.4 mm or larger, and must be printed from very dry filament below 15% RH. QIDI does not recommend it in the QIDI Box or any PTFE-fed multi-material system, so we feed it from a sealed dry box on a single extruder path. That rules out multi-color or soluble-support combinations in one print.

If you need even more, QIDI's UltraPA-CF25 (PPA-CF25) is a higher-end sibling with 25% carbon fiber, which we can quote on request; details are in the FAQ below.

PAHT-CF is very stiff. QIDI's blog lists Young's modulus of 7492.51 MPa as printed and 8114.10 MPa annealed, and bending modulus around 7 GPa, which is close to double PA12-CF. Bending strength of 144.00 MPa as printed is the highest in our nylon range apart from UltraPA-CF25.

Annealing raises stiffness and heat resistance, but it reduces toughness. QIDI's notched Charpy impact falls from 10.37 kJ/m² as printed to 5.62 kJ/m² annealed, and recovers to 8.61 kJ/m² after the annealed part absorbs moisture. Elongation at break drops from 1.92% to 1.52%. So an annealed part is stiffer and handles heat better but is more brittle under sharp impacts.

Anisotropy, meaning different properties in different directions, is pronounced. QIDI lists tensile strength of 93.15 MPa in XY versus 51.03 MPa in Z, so layers are the weak plane. Fibers also align along the toolpath, so loads along printed lines are carried best. We orient parts accordingly and need to know your load direction.

Creep resistance is good for a printed plastic, especially annealed, so it holds bolted joints better than unfilled nylon. Still, use metal inserts and washers rather than relying on the plastic alone under heavy, constant clamping loads.

HDT, the heat deflection temperature, is the temperature at which a standard bar bends a set amount under a fixed load: 0.45 MPa for a light load and 1.80 MPa for a heavier one. QIDI's blog gives PAHT-CF both. As printed: 84.8 °C at 0.45 MPa and 82.0 °C at 1.80 MPa. Annealed at 100 °C for 8 hours: 190.7 °C at 0.45 MPa and 117.5 °C at 1.80 MPa.

Two points matter for buyers. First, unannealed parts don't have the high-heat performance this material is known for; if heat is the reason you chose it, budget for annealing. Second, the heavier-load figure is much lower than the light-load one, so a heavily stressed part in heat has far less margin than the 190.7 °C headline suggests.

Moisture affects these values. After the annealed part absorbs water to saturation, QIDI reports 194.5 °C at 0.45 MPa but 101.5 °C at 1.80 MPa. Plan around the moisture-saturated, heavier-load number for parts that are both humid and heavily loaded.

Annealing can shrink parts slightly; QIDI advises measuring a test piece before and after. We anneal only by agreement, and we test a sample first when dimensions are critical.

Carbon black and fiber give PAHT-CF reasonable UV resistance compared with unfilled nylon. Long-term sun can still fade and chalk the matte surface and expose fibers; a UV-resistant coating helps for cosmetic parts.

Weather means moisture, too. QIDI's saturated water absorption of 1.37% is lower than PA12-CF's, but outdoor parts will still absorb some water, which reduces stiffness slightly and lowers heavy-load heat resistance.

PAHT-CF generally resists oils, greases, fuels, coolants and many solvents, and QIDI markets it for chemical resistance. PPA-based materials are generally more resistant to hot water and automotive fluids than PA6 or PA12.

Strong acids and oxidizers generally attack polyamides, including PPA. If your part will sit in a specific fluid at temperature, tell us and test a sample before ordering a batch.

PAHT-CF is very moisture-sensitive during printing: QIDI warns that absorbed moisture causes oozing, bubbles and rough surfaces. We dry it at 80–100 °C for 4–6 hours and keep it below 15% RH while it prints, fed from a sealed dry box. QIDI ships it in vacuum foil packaging for the same reason.

Once printed, parts take on some water. QIDI's wiki, quoted in its PAHT-CF guide, says nylon parts in humid air or water gradually lose some strength and stiffness and become tougher, especially thin, slender parts. QIDI's own figures show this: annealed impact strength rises after moisture saturation, while heavy-load HDT falls.

PAHT-CF prints with a deep matte black finish that hides layer lines well and looks technical. Supported surfaces are rougher than top and side faces.

Very fine details are softened by the 0.4 mm minimum nozzle. Color is generally black only.

Annealing is the key post-process and is done only by agreement. Parts can be drilled, reamed and tapped; heat-set inserts work well at suitable temperatures. Sanding works but exposes fibers, and carbon dust should be handled with a mask.

Vapor smoothing isn't something we offer for this material. QIDI advises removing supports from PA parts within 2 hours of printing, which we do on our side.

Fiber reinforcement keeps shrinkage and warping low, so PAHT-CF holds dimensions well as printed, and QIDI claims it prints without warping. Annealing can shrink parts slightly, so finish critical fits after annealing or let us test first.

Holes print undersized as with all FDM parts. PAHT-CF drills and reams cleanly, so design precise holes slightly undersized and ream to size.

Moisture uptake after printing is lower than with PA12-CF, so dimensions drift less in humid environments, but they still shift a little. For bearing seats and precision fits, tell us the tolerance you need; we'll recommend whether to ream, anneal first or condition the part before final measurement.