Poly(ether ether ketone)s processed through extrusion-machining and 3D printing: A comparative study on mechanical, thermal and fracture properties at ambient and cryogenic environments

Poly Ether Ether Ketone (PEEK) is a very promising engineering thermoplastic material having capability to perform over wide service temperatures from cryogenic to around 300 degrees C. Processing of PEEK is a challenging task, owing to its physical, thermo physical properties and chemical nature. The present paper envisages processing of PEEK by two different techniques viz, 3D printing and extrusion and assessment of properties of respective specimens at 30 degrees C and -196 degrees C. Thermal and mechanical properties and fracture morphological features of PEEK specimen, processed using these techniques are compared. Samples processed by extrusion possessed higher mechanical properties both at 30 degrees C and -196 degrees C. The 3D printed samples, though exhibited inferior strength and modulus, showed significantly higher elongation (150-250%) at 30 degrees C. All samples showed ductile fracture behavior at 30 degrees C. At -196 degrees C, the fracture morphology got transformed in to a pattern typical of brittle materials, as expected. Extruded specimens showed lower thermal expansion coefficient compared to the 3D printed specimens. Thermal expansion characteristics were different in the X, Y and Z directions for 3D printed specimens due to the anisotropy resulting from printing direction which is corroborated by the morphological studies. The results of this investigation enable designing and fabrication of PEEK based structural components of desired geometries for various applications.