PA-CF, PPA-CF or PEEK-CF?
Short answer: PA-CF covers the majority of functional components used at temperatures up to approximately 100 °C and is the most cost-effective of the three variants. PPA-CF can be used continuously at higher temperatures up to around 180 °C, making it the material of choice for engine compartments and drive systems. PEEK-CF starts above this and extends to a continuous operating temperature of 260 °C, in addition to contact with aggressive chemicals and components subjected to tribological stress. The choice of material rarely depends on tensile strength, but rather on temperature, medium, and budget.
PA-CF, PPA-CF or PEEK-CF in numbers
All values are taken from our material data sheets, measured on printed test specimens from the respective filament manufacturers.
Key figure | PA6-CF15 | PPA-CF25 | PEEK-CF30 |
Fiber content | 15% | 25% | 30% |
Density (g/cm³) | 1.25 | 1.23 | 1.41 |
Tensile strength XY (MPa) | 110 (0°) | 121 | 169 |
E-modulus of train XY (MPa) | 10,500 (0°) | 10,220 | 17,310 |
Elongation at break XY (%) | 0.98 | 1.6 | 3 |
Glass transition temperature Tg (°C) | 68 | 80 | 143 |
HDT 1.8 MPa (°C) | 120 | 126 (tempered) | n/a |
HDT 0.45 MPa (°C) | n/a | 199 (tempered) | n/a |
Maximum continuous operating temperature (°C) | approximately 100 | approximately 180 | 260 |
Water absorption (%) | > 0.3 (24 h) | 1.09 (ISO 62) | 0.50 (ISO 62) |
Test standard train | ISO 527 | ASTM D638 | ISO 527 |
A preliminary note to put part of the table into context: The tensile strength values for PPA are determined according to ASTM D638, while the values for PA and PEEK are based on ISO 527. These two standards specify different specimen geometries and testing speeds. Therefore, a comparison down to the last percentage point is not permissible. For material selection, considering the order of magnitude is sufficient; for design purposes, you should use the value specified in the standard according to which the calculation is performed.
The second point is the more interesting one: At room temperature, PA6-CF15, with a Young's modulus of 10,500 MPa, is practically as stiff as PPA-CF25 with 10,220 MPa. If stiffness alone is considered, the use of the more expensive material cannot be justified. The crucial difference lies in its behavior at temperatures above 80 °C.
PA-CF: the all-rounder for everything up to 100 °C
PA6-CF15 and PA12-CF15 are the workhorses of functional FFF printing. They are characterized by high stiffness, good resistance to oil, grease, and fuel, minimal warpage in large-format components, and moderate material costs. For fixtures, gauges, holders, housings, and functional prototypes, they are the right choice in nine out of ten cases.
The limiting factor is thermal resistance. The glass transition temperature of PA6-CF15 is 68 °C. Above this temperature, the matrix softens. While the fibers continue to provide structural stability, the stiffness of the component measurably decreases. The heat deflection temperature of 120 °C at 1.8 MPa is a standard value under defined bending stress and does not imply suitability for continuous use at 120 °C. We consider the practical upper limit to be around 100 °C, and below that for significant mechanical loads.
Within this category, PA6-CF15 is recommended for applications requiring maximum stiffness, as well as for planar components subjected to in-plane loading. PA12-CF15 is suitable for lightweight structures with a density of 1.07 g/cm³, for tougher components, clips and snap connections, and for all applications where moisture absorption affects dimensional stability. An important note regarding PA12-CF15: Our data is based on the manufacturer's reference values and not on printed test specimens. The stated HDT values are very close to the melting point and are not to be expected in a printed component.
Furthermore, a note on anisotropy. This affects all three materials, but is particularly evident here: PA6-CF15 reaches 110 MPa in the path direction (0°) and 70 MPa perpendicular to it. In this case, the path orientation has a greater influence than the choice of material.
PPA-CF: the automotive class between 100 and 180 °C
PPA, a semi-aromatic polyphthalamide, bridges the performance gap between PA-CF and materials such as PPS and PEEK. Typical automotive applications include engine compartment components, charge air and cooling systems, sensor and connector housings, motorsport components, and test fixtures for temperature-controlled environments.
PPA-CF25 exhibits a tensile strength of 121 MPa, a modulus of elasticity of 10,220 MPa, and a flexural strength of 185 MPa. The filament has a core-sheath structure: the fibers are located in the core, while the sheath consists of fiber-free PPA. Its water absorption according to ISO 62 is 1.09%, a value significantly lower than that of an aliphatic PA 6 until saturation. This is a crucial advantage for manufacturing dimensionally accurate components for use in humid environments.
A crucial detail regarding PPA is not found in the main table, but in a footnote: The specified properties apply to tempered components. Untempered, the heat deflection temperature of PPA-CF25 is 97 °C (test stress 0.45 MPa), while tempered this value increases to 199 °C. This corresponds to a difference of more than 100 K for the same component. Those who use untempered PPA have paid the additional cost compared to PA-CF without gaining the high-temperature material. Conversely, tempering comes at the expense of toughness: The Charpy impact strength drops from 13.1 to 7.3 kJ/m², a decrease of more than 40%.
The temperature rating is equally important. The value of 199 °C applies to a test voltage of 0.45 MPa, while the datasheet specifies a value of 126 °C for 1.8 MPa. Both values are correct, but the value corresponding to the specific temperature rating is decisive for the design. If electrical insulation or a light component color is required, PPA-GF15 from the same product family is the more suitable choice, as it has a lower anisotropy of 1.41:1. For true ESD protection with proven surface resistance, we offer PA612-ESD, although this material exhibits the temperature limitations typical of PA materials.
PEEK-CF: High-end, when the requirement demands it
PEEK-CF30 exhibits a tensile strength of 169 MPa and a modulus of elasticity of 17,310 MPa. This corresponds to a stiffness approximately 65 to 70% higher than that of the other two materials. The glass transition temperature is 143 °C, the continuous service temperature is 260 °C, and the melting point is 343 °C. Furthermore, the material offers superior chemical resistance compared to PA and PPA, tribologically optimized properties for sliding and wear applications, and semi-insulating electrical properties, a beneficial characteristic in ESD-sensitive environments. Typical applications include aerospace, defense, the chemical and process industries, and test bench construction.
Two limitations must be considered. First, the anisotropy: The values in the XY plane are 169 MPa and 17,310 MPa, while in the Z direction they are only 71 MPa and 4,165 MPa. The fibers reinforce the web, not the interface between the layers. In PEEK-CF, the drop in stiffness perpendicular to the web is most pronounced, by a factor of four. This makes component orientation a design aspect and not merely a manufacturing issue.
Secondly, consider this option: If biocompatibility, compliance for food contact according to Regulation EC 1935/2004, or maximum toughness are required, then unreinforced PEEK 450 natural with an elongation at break of 19% is not the right material. For applications requiring increased stiffness with electrical insulation, GF-PEEK is the appropriate choice. Within the PEEK product family, carbon fiber is a choice based on stiffness and tribology, not automatically the best PEEK variant.
Regarding the budget: PEEK is significantly more expensive than PPA, while PPA is in turn significantly more expensive than PA-CF. For larger components and small production runs, we reduce costs by using the FGF (Fused Granulate Fabrication) process on our ExAM-510 system. Granules are considerably more cost-effective than filament, and the build volume reaches up to approximately 510 × 510 × 410 mm. We manufacture PA-CF and PPA-CF components using the FFF process with dimensions of up to 350 × 350 × 450 mm.
Three questions that decode every datasheet number
Tempered or untempered? For PPA, this determines approximately 100 K of heat resistance; for PEEK, it determines crystallinity, strength, and dimensional stability during operation.
At what load level? HDT at 0.45 MPa and HDT at 1.8 MPa often differ by 70 K. The decisive factor is the actual temperature level present in the component.
In which direction? XY values are path values. The layer boundary in Z carries significantly less tensile strength in fiber-reinforced materials, only around 40% in PEEK-CF.
Decision based on five questions
Ask | PA-CF | PPA-CF | PEEK-CF |
Continuous operating temperature | up to approximately 100 °C | 100 to 180 °C | up to 260 °C |
Media contact | Oil, grease, fuel | additionally hot air, coolant | additionally aggressive chemicals, steam |
Stiffness requirement | high (10,500 MPa) | high (10,220 MPa) | very high (17,310 MPa) |
Sliding and wear load | no | conditional | Yes, tribologically optimized |
Budget | cheapest class | middle class | highest class, FGF defused |
As a rule of thumb: start with PA-CF and only switch to a higher-grade material if a specific requirement necessitates it. The most common mistake in material selection is not choosing a material that is too weak, but one that is too expensive. This is usually triggered by peak temperatures that only occur for a few minutes a year, or by stiffness requirements that could just as easily have been met by a stiffening rib on the component.
What this means for your request
To provide a reliable recommendation, we need three pieces of information: continuous and peak temperatures and their respective durations, the concentration and temperature of the medium, and the direction of the component load. Based on this information, the material class can usually be determined during a phone call, including whether tempering is required as part of the manufacturing process.
Our material data sheets for PA-CF, PPA-CF and PEEK are available as PDFs upon request and contain all test standards and footnotes. Please contact us at info@malping.de .
Frequently Asked Questions
What are the differences between PA-CF, PPA-CF and PEEK-CF?
All three are carbon fiber-reinforced thermoplastics for FFF printing; they differ in temperature resistance. PA-CF can be used up to approximately 100 °C, PPA-CF (tempered) up to around 180 °C, and PEEK-CF up to a continuous operating temperature of 260 °C. Stiffness and price increase in the same order, but the significant jump in stiffness only occurs between PPA-CF and PEEK-CF.
Up to what temperature can I use PA-CF?
The practical upper limit for PA6-CF15 is around 100 °C, and lower under significant mechanical load. The glass transition temperature is 68 °C; above this temperature, the matrix softens. The datasheet value of 120 °C is a standard heat deflection temperature of 1.8 MPa and does not indicate approval for continuous operation.
Why is PPA-CF more expensive than PA-CF if the stiffness is the same?
At room temperature, it is indeed 10,220 MPa compared to 10,500 MPa. The difference arises above 80 °C. When tempered, PPA-CF25 maintains a heat deflection temperature of 199 °C at 0.45 MPa, while PA6-CF15 is already well above its glass transition temperature in this range. Anyone not exceeding 100 °C doesn't need PPA.
Does PPA need to be tempered after printing?
Yes, if high-temperature properties are required. Untempered, PPA-CF25 achieves a heat deflection temperature of 97 °C at 0.45 MPa; tempered, it reaches 199 °C. Tempering also reduces the Charpy impact strength from 13.1 to 7.3 kJ/m².
How much does the strength of PEEK-CF decrease in the Z-direction?
PEEK-CF30 achieves a tensile strength of 169 MPa and a modulus of elasticity of 17,310 MPa in the XY plane, and 71 MPa and 4,165 MPa, respectively, in the Z direction. This represents approximately 40% of the strength and about a quarter of the stiffness. Therefore, component orientation should be considered during the design phase, not during work preparation.
Which PEEK variant is suitable for medical technology or food contact?
Unreinforced PEEK 450 natural. It is biocompatible, suitable for food contact according to EC 1935/2004, and with an elongation at break of 19%, it is the toughest PEEK variant. PEEK-CF is the choice for stiffness and tribology, while GF-PEEK is used for electrical insulation with increased stiffness.
How large can the components be?
We manufacture PA-CF and PPA-CF using the FFF process up to 350 × 350 × 450 mm. We also produce PEEK using FGF granule printing on the ExAM 510 up to approximately 510 × 510 × 410 mm, which significantly reduces material costs for larger components and small production runs.
What information does Malping need to recommend a material?
Continuous and peak temperatures with their respective time fractions, the medium with its concentration and temperature, and the load direction within the component. With these three pieces of information, the material class can usually be determined in a single phone call.
Author: Dr.-Ing. Bastian Gaedike, Founder and Managing Partner, Malping GmbH, Neuhausen auf den Fildern | malping.de | #MATERIALPENGUIN
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