PEEK vs PEKK vs PPSU vs Ultem (PEI)

PEEK, PEEK CF, PEKK, PPSU and Ultem (PEI) are all high performance polymers offering dimensional stability, heat resistance, high strength and broad chemical resistance. All of these filament materials are also UL 94-V0 rated – self-extinguishing in <10 seconds. 



PAEK refers to all the materials within the Poly Ether Ketones family, including PEEK, PEEK-CF and PEKK.

Whilst both PEEK and PEKK have high mechanical strength, high temperature resistance, fatigue resistance and low flammability, chemical differences exist. The molecular structure of PEKK provides higher heat resistance than PEEK – a heat deflection temperature (HDT) of 160°C versus 145°C. PEKK is inherently more expensive compared to PEEK.

PEEK, PEEK CF, PEKK, PPSU and Ultem (PEI) Filament

PEEK-CF is PEEK reinforced with carbon fibre – this improves the stiffness and compressive strength enormously which makes this material suitable for dynamically stressed parts. Furthermore, HDT is significantly higher than PEEK and even PEKK, at 280°C.

Ultem is the brand name for PEI products. A key difference between PEEK and Ultem is their different morphological structures – Ultem is amorphous while PEEK is semi-crystalline. This influences the performance at elevated temperatures. 


The biggest difference between these two plastics is cost. PEEK is one of the most expensive polymers on the market, on the other hand, Ultem offers comparable properties at lower cost. In regards to heat resistance, whilst Ultem offers continuous use up to 170 ºC, PEEK can operate well above 250°C without deforming. This makes PEEK more suited to high-load, high-temperature applications. Ultem is more easily (post)-processed than PEEK, which typically requires CNC milling for machining purposes.

PPSU is similar to Ultem in that it is a similar material that is also amorphous, but exhibits impact resistance and chemical resistance superior to Ultem. It can operate in temperatures up to 180°C and offers an excellent resistance to hydrolysis, making it perfectly suited to plumbing applications. Versus PEEK, PPSU is inferior when it comes to compressive strength, tensile strength and elasticity

Mechanical Properties Overview

ProductTensile strength at yieldTensile strength at breakElongation strain at breakElongation strain at yieldTensile (E) modulusFlexural strengthFlexural modulus
PEI ULTEM 908588 MPa (ISO 527)71 MPa (ISO 527)50% (ISO 527)6.7% (ISO 527)3050 MPa (ISO 527)90 MPa (ISO 178)2750 MPa (ISO 178)
PEI ULTEM 1010105 MPa (ISO 527)54 MPa (ISO 527)60% (ISO 527)6% (ISO 527)3200 MPa (ISO 527)160 MPa (ISO 178)3200 MPa (ISO 178)
PPSU77 MPa (ISO 527)77 MPa (ISO 527)60-120% (ISO 527)7.3% (ISO 527)2410 MPa (ISO 527)108 MPa (ISO 178)2380 MPa (ISO 178)
3F PEEK CF 9676126 MPa (ISO 527)3.9% (ISO 527)7800 MPa (ISO 527)
3F PEEK 958197 MPa (ISO 527)5% (ISO 527)3800 MPa (ISO 527)145 MPa (ISO 178)3400 MPa (ISO 178)
3F PEKK 5008290 MPa (ISO 527)5% (ISO 527)3000 MPa (ISO 527)150 MPa (ISO 178)2500 MPa (ISO 178)


Thermal Properties Overview

ProductVicat softening temp.Heat deflection temp
PEI ULTEM 9085173°C (ISO 306)152°C (ISO 75)
PEI ULTEM 1010211°C (ISO 306 B50)200°C (ISO 75-2)
PPSU207°C (ASTM D648 1.8MPa)
3F PEEK CF 9676280°C (ISO 75)
3F PEEK 9581145°C (ISO 75)
3F PEKK 50082160°C (ISO 75 – Printed)


Filamentive PRO is a specialised portfolio of high performance and engineering 3D printing filament for industrial applications.

Filamentive PRO currently offers the following filament for 3D printing: